Rebuilding Power Head

[MASTER Brian]

Re: Rebuilding Power Head

Well, I went out and pulled the plugs and tried looking into the cylinders. Several of the plugs looked very black and sooted up. The others appeared to be on their way to getting that way. I wonder if some of the poor performance wasn't fouled plugs from the double oil, assembly lube, etc. I can't tell about the pistons, because of their shape.

I'll perform a compression and spark test later. Then track down the fuel leak and the linkage issue.

 

[funpilot]

Re: Rebuilding Power Head

Brian, here is a thread on my spark tester: I like it because I can see the spark on each cylinder while linking and synching.

http://forums.iboats.com/bbBoard.cgi?a=viewthread;fid=28;gtid=1139916;gpid=1140215#gpid1140215

When I first ran my rebuild, I was only able to get 4700 RPM on it, but a link and synch took care of that. Now as soon as I have time and I stop playing with the Jet Boat I'm going to experiment with motor height as I top out at 5200 RPM. And, as I check my GPS speed against a theoretical slippage of 10% my tach could be indicating low.

If you are leaking fuel you could have a high float, or a bad hose or a recirculation problem such as a bad check valve or unconnected hose. Leaking fuel could also mean a lean condition to a cylinder, but if all your plugs are dark, I doubt it.

Run it on muffs or in a tank and see if you can observe where the fuel is coming from. As KYHunter said, you did rebuild the carbs, right?

fp

 

[MASTER Brian]

Re: Rebuilding Power Head

Thanks fp, that is helpful. My only question is about the ground wire(s). It looks like you put "eye" terminals on each ground on the board, then tied them all together and ground on one point at the motor. Is that correct? Also, you mentioned the allegator clip vs. the eye terminal on the engine side. Will that provide enough of a ground for the whole board?

I did not do a complete rebuild on carbs, only because I don't have the gauge needed to do this. I am trying to find one, but am unsure if this is a universal gauge or something that has to be from OMC. The gauge I'm speaking of is the one that checks the float. I did check the rest out and made sure what I had apart was clean and looked good, but I didn't replace the little misc pieces. I didn't want to do this in stages. Maybe I should have and I will do all this. It was just very obvious these had fairly recently been done. Were they done correctly? I don't know, but the guy I bought it from wasn't the type to do the work himself, which leads me to believe he had a shop do it and based on the markings, it was obvious they seemed to know what they were doing. Being my 1st out board carb rebuild, I trusted them more than myself I guess.

As for timing, I tried to set the timing, by the method described in the link and sync, but I never hooked it to a timing light. The main reason on that is that it looked like the motor needed to be ran at full throttle and being as it's a fresh motor that hasn't been broken in, that didn't seem right. Maybe I mis-read something.

I'll go back over the sync and link and see if I missed something or set it incorrect. I had a friend helping, maybe we mis-communicated on something!!

Why wouldn't the prop engage in reverse? That seems like a lower unit issue and not a sync issue. I say this, because I can unhook the cables and manualy shift it and the prop free spins when it should be inreverse. Maybe the shift rod to the connection at bottom of power head is wrong. We did fight getting that hooked up for some time. Very tight fit to get to.

I checked compression this AM and I'm not sure if I should be worried or not. I got around 90 psi +/- a few psi on each cylinder. I'm hoping this is because the rings haven't set yet. Like I said it hasn't been run long, maybe 15-20 minutes total and not very high RPM's. I also don't seem to be getting full throttle opening. I did read somewhere on here that you don't need full throttle to do a compression check, but I always seem to get higher compression the more the carbs are opened.

I checked all plug boots, etc were tight, but I would also be shocked if several of those plugs weren't fouled. I'll clean/replace them and test that spark.

Regarding the "Maximum Spark Advance Adjustment" is this crucial? I ask because the manual states to do this with a test wheel, not a prop. I guess this is also the step that says to connect a timing light to the No. 1 cylinder. It says a minimum of 5000 RPM's. I'm at the step in break-in with a maximum of 3000 RPM's.:/

As for the fuel leak, I didn't put the gasket or all the bolts in that hold the front cover of the carb cover in. I set the cover on with a few bolts just to keep water from being able to splash up. This is where the fuel seems to be dripping from. I did get fresh fuel to that spot when doing the compression test. I plan on pulling that cover and seeing if I can find the problem/source. Could the auto choke be causing this?

Basically at this point, my game plan is to unhook the linkages and see if I can find reverse. Look for the fuel issue, check spark and then reset the timing and the sync and link. I'll also likely get some new plugs and if I can get the gauge do the carb rebuild. Any other recommendations?

 

[KYHunter2]

Re: Rebuilding Power Head

Brian,

You can get the timing very close or right on , by doing Joe reeves method.

Basically, you need to remove and ground the plugs, advance the throttle to wide open, turn over engine and set 4 degrees after recommended timing.

Thats it basically, but do a search , I may have missed a step.

You'll need to verify on the lake , either tied to trailer , or going down the lake at WOT.

But, I've never had a problem running motor through breakin , then checking at WOT.

You told me in an earlier reply that you verified it was going into reverse, didn't you ?

Yes max spark advance and everything else in the link and sync. is CRITICAL.

You wont get any higher compression at WOT, then you will doing it with all plugs out.

I've never even heard of checking it with motor running.

Yes when your rings seat your compression will go up .

You also know that the wiseco pistons must be warmed up before your comp. reading will be correct.

All comp. tests are more accurate on a warmed up motor , but with wiseco's its even more crucial, because there forged.

The carbs don't effect compression readings.

Again anything but a thorough and complete rebuild of carbs , is NO GOOD !

With the money you have in the rebuild, its rediculous, and VERY risky , to not rebuild them.

You don't have to have the guage, most kits come with a paper one thats ok.

Not really needed though .

Set floats level with the carb base or ever so slightly higher.

And be sure there level across the front of float to carb .

The choke solenoid , should have been checked during link and sync.

There are no short cuts to the procedure, it must be followed to the letter in the order given.

If you keep taking shortcuts, ie: carb rebuild , timing not set , max advance , etc.

Your going to be right back where you started , with a ruined motor.

Please do these things correctly and completely,
Its A MUST !!!

One more thing you said its only run 15 - 20 min.

What the heck breakin procedure are you following, because its not RIGHT.

Your idle breakin alone is more then 15-20 min.

Brian , check your pm's
KYHunter

 

[funpilot]

Re: Rebuilding Power Head

Brian, correct on the spark tester grounds. Use a decent size allegator clip, doesn't have to be huge, it is a lot of voltage but little current.

If you can shift it in reverse with the cable disconnected, you have to adjust the thumb nuts on the motor end of the cable to shorten the housing relative to the cable to get it to go into reverse when operating it with the cable and throttle, and then check to make sure that it goes into neutral and forward properly. If it doesn't, the shift rod is at the wrong height.

I also agree with everything KTHunter says. except that you set the timing four degrees after the recommended timing. i.e, if your timing is to be 28 degrees, you use 24 degrees. The powerpack senses a less than full RPM condition and retards the timing about that much, to save the engine in the event of a timing problem. Since you are turning it over at much less than 5500 RPM on the starter during the 'Joe Reeves' method, you have to use the more retarded value. Under actual conditions the timing will jump to the proper value.

Use the timing light during the link and synch, spark plugs hooked to the tester. Do the synch first so you know the carbs are opening together and going to WOT, and then do the link adjustment for the timing and idle.

fp

 

[KYHunter2]

Re: Rebuilding Power Head

Sorry my fault , typed it wrong. Brain fart. I meant minus 4 degrees . Just worded it arse backwards.

As funpilot said it will make up the 4 degrees, its amazing how accurate it is.

Just be sure to verify after breakin.

Edit : I corrected my error.

KYHunter :$

 

[MASTER Brian]

Re: Rebuilding Power Head

I will print these out tomorrow and follow them. I put together a spark tester and I got a chance to weld up a better piston stop tool.

KY, I'm following what Wiseco told me as well as the manual on the break-in. I'm not anywhere near finished and barely even started. I may be off on the time I typed, it was a quick guesstimation after a long day and somewhat sleepless night.

Here is what I did. I backed boat on trailer into water and ran through 3 heat cycles per wiseco's instructions. I'm not sure of the exact time on that. I was told to start the motor up, let idle until operating temp, then shut down and allow to cool. I did that 3 times, then after that. I loaded the boat in the water and idled it for another 5 minutes or so, then got the boat on plane and varied the throttle at under 3000 RPM's. I ran it that way probably another 5 minutes, before it lost a bit of power and I then ideled it back to shore and loaded her up.

The manual calls for 10 minute high idle. I figure that was covered with the wiseco instructions and the idle out of the no-wake area. Wiseco acted as though once done with their heat cylce, I was ready for low speed runs.

The carb kit didn't have a gauge, I'll see if the dealer has/can get one fairly quickly. Otherwise I'll just go with your recommendation on that.

As far as reverse, I had it before all this happened and I was sure I had it when I put all this together yesterday. At least I thought I did. At this point, I'm 2nd guessing that though...

I hope I didn't miss anything.

 

[MASTER Brian]

Re: Rebuilding Power Head

KY, I checked the PM's but didn't find anything. Let me know if I need to check it again.

 

[KYHunter2]

Re: Rebuilding Power Head

Im not trying to say the breakin your following is wrong.

It just seems like a short idle breakin to me.

Some say with the new components today a breakin is not needed.

I run mine for an hour at various idle rpm's.

Instead of typing it all .

This is from the Max rules site , and is basically what I've followed, with good results.



Powerhead Break-In Recommendations

Break In Your Motor Right!

Before starting your overhauled engine please do the following:

Test/replace the thermostat(s). Pressure relief bypass valves should be serviced for correct operation.
Examine or Replace the water pump.
Retard the timing 2-4 degrees. This can be done on most engines by turning in the timing screw towards the timer base 2-4 turns.
Check to be certain you have the correct heat range spark plugs.
Make sure you have fresh, clear 89 octane premium fuel and TCW-III oil -- I strongly recommend using oil supplied by one of the major engine manufacturers. e Even better are the newly available synthetic blend oils as they will prevent carbon accumulation. Cheap oil and gas are a false economy on modern engines. I recommend extra oil for the first 10 hours -- double oil seems to foul the plugs and 1 ½ oil seems to work.
Check the high speed jet sizes in the carburetor. Check for the latest factory recommendations and use them or one size larger.

Break-in Procedure
Start your engine at home base using flush muffies to see that it actually does start and doesn't have any obvious problems i.e. - water leaks, etc... Once it is obvious the engine will start and run I suggest the engine be put in the lake and run for 20 minutes at high idle RPM (750 - 850) unloaded or out of gear. Check the plugs and carefully feel the engine to make sure it is not overheating. Restart the engine and then move it up to around 1500 RPM loaded in gear and vary the speed from idle until you have two hours on the engine. All the foregoing may be accomplished on the trailer. It is time consuming and tedious but it is the basis for long and happy engine life. If everything seems to be okay check the timing on #1 & #2 cylinders on a V-4 or V-6. Use the cylinder with the highest reading and set the timing 2-4 degrees less than the factory specs. If the spec is 24 degrees BTDC set the engine at 22 degrees. Leave the engine at this setting for the break-in period. If later you want more power the timing can be advanced to the factory spec but the engine will live longer if you leave the timing retarded. Don't guess. Use a timing light and set the timing UNDER LOAD, at FULL ADVANCE! Don't run it there other than to check the timing.

At this point you can run the boat, cruise at 3000-3500 RPM, periodically giving it short runs up to full throttle. This should continue until there are ten hours on the engine, then your powerhead should be broken in. If you follow the outlined procedures you will get better service from your engine. Be sure that at maximum throttle the engine will turn up to 5500 RPM, the top operating RPM for most 2 strokes. If it doesn't the propeller should be changed until the engine runs at or slightly over the rated operating range with a light load. The wrong prop can cause the motor to lug, overheat or at the other extreme over rev and destroy all your good work. Be sure to check and retorque the cylinder head gaskets.

Rebuilt Motor DO's and Don'ts
You must determine the reason the original powerhead failed. If the problem is not identified and corrected it is almost certain the newly rebuilt powerhead will fail. If a restricted (lean) carburetion problem caused the original powerhead to fail, the new one will also fail unless the problem is corrected. Guaranteed!

The most common causes of engine failure are detonation, pre-ignition, and overheating or any combination thereof. The result of these problems is that the temperature in the combustion chamber gets too high. As soon as the temperature in the chamber gets higher than normal the engine begins to run poorly and the damage to the engine begins. Detonation is usually caused by the air/fuel mixture being lean and the erosion of the piston starts at the edge or outer diameter of the piston. If the erosion starts in the center of the piston it is probably an ignition problem. An engine running hot due to deteriorated water pump or cooling system blockage compounds the problem.

The other common failure mode I see is scuffing and/or cold seizure which occurs mostly in new or rebuilt engines. When the engine is started, the piston heats up and expands quicker than the cylinder walls which are liquid cooled. When the engine is broken in and running at the correct operating temperature it runs with around .002 clearance. Normal human hair is about .003 inches. Once the rings are seated and a glaze forms on the cylinder walls this problem is not likely to occur. This makes the break in period very critical. The proper break in of a new or rebuilt powerhead will help insure that you get good value from your investment.


The only thing I do different is the hour at idle. And try to get rpms closer to 6k.

Also I use dbl. oil , fouling hasnt been a problem.

As far as the section on changing the prop, theres more to it then that.

When you get to the set-up, part of your engine/boat.

There are some experts here, that can help you get your rpm's ,where they need to be.

Thats who I ask.

KYHunter

 

[MASTER Brian]

Re: Rebuilding Power Head

KY, thanks. I need to print all of this out, so I have it.

I should have 15 minutes or more, most likley more, on my engine at a higher idle unloaded. I can't say for certain on that only because I did not time that part, because I was only allowing the cylinder to get hot and then I left it there for a few minutes and shut it down. I'd guess from 5-8 minutes each time for 3 times. Not near as much as your hour, but what my manual calls for.

After reading your article, I see where you are coming from.

I'll back track to the beginning of the link and sync and let you know how things go. I'll also go through the carbs fully. It may be a few days, but I'll post any findings I have. I have a spark tester ready to go, as well as a GOOD piston stop tool.

Thanks once again for all of the help.

 

[MASTER Brian]

Re: Rebuilding Power Head

I hope that didn't sound like I was arguing with your recommendation on the hour, I was just saying I did what I thought Wiseco and OMC suggested. Sort of a combination of the two anyway. Your method seems very good and thorough and I'll probably follow it from here on out.

As for the Joe Reeves method, I'm trying to find that. I can't ever get the search functions on these forums to work for me. After spending an hour, I came up with a date of the post, but the search won't let me go that far back!!:% Luckily I found Joe Reeves email addy, so I sent him an email. Hopefully he responds or someone can point me in a better direction on this.

One question I did come across is the "quick start" feature. I guess it interfere's with Joe Reeves' method. Does my boat have that? I know the manual says something about an auto timing advance at higher RPM's???

 

[MASTER Brian]

Re: Rebuilding Power Head

It looks like I finally found it....

Joe Reeves -

- Re: Test Tank/Ignition Testing? (1:36pm 10 Sept '03)
Mako171.... You can blow up to a couple thousand on the type test tank you're speaking of.

However, you do not need to run the engine as the manual states. The timing can be checked and set as follows.

(Timing At Cranking Speed 4°)
The full spark advance can be adjusted without have the engine running at near full throttle as follows.

To set the timing on that engine, have the s/plugs out, and have the throttle at full, set that timer base under the flywheel tight against the rubber stop on the end of the full spark timer advance stop screw (wire it against that stop if necessary).

Rig a spark tester and have the spark gap set to 7/16". Hook up the timing light to the #1 plug wire. Crank the engine over and set the spark advance to 4° less than what the engine calls for.

I don't know the full spark advance setting your engine calls for, but to pick a figure, say your engine calls for 28°, set the timing at 24°. The reasoning for the 4° difference is that when the engine is actually running, due to the nature of the solid state ignition componets, the engine gains the extra 4°.

If you set the engine to its true setting at cranking speed, when running it will advance beyond its limit by 4° which will set up pre-ignition causing guaranteed piston damage! You don't want that to take place.

No need to be concerned about the idle timing as that will take care of itself. The main concern is the full advance setting.

Be sure to use your own engines spark advance settings, not the one I picked out of the air here in my notes. Good luck.......

[/quote]

Joe Reeves

- Re: Test Tank/Ignition Testing? (5:09pm 11 Sept '03)
Clanton is correct. It had slipped my mind about the "Quick Start" feature. That feature would need to be disabled in order to use the 4° timing procedure that I mentioned.

[/quote]

So, does my engine have this feature? If so, how do I disable it??

 

[MASTER Brian]

Re: Rebuilding Power Head

Well, I found my fuel leak, it was where the fuel line leaving the pump, meets the inlet that feeds the carbs. That could explain low power.

I also found why I don't have reverse. The shift rod is obviously too low. I don't understand why, but it obviously is. Now for the tedious task of trying to turn the rod, while the PH is on. I don't want to pull the LU anymore, unless I absolutely have to. I just feel the more I pull it, the better chance for a stripped thread.

Did we decide that in gear is in gear, meaning that if it shifts and I get reverse, neutral and forward, that I'm good or is there a point, I'll get slippage if it's not far enough?

 

[MASTER Brian]

Re: Rebuilding Power Head

Well, I am hoping I have the rod in the correct place. If not I shouldn't be more than 1 turn up or down. Tomorrow, I plan on hooking up the linkages and trying it out. I don't have the carbs on right now, so I couldn't hook the linkages up, but I can move it and get it to go in foward, neutral and reverse.

 

[funpilot]

Re: Rebuilding Power Head

Brian, listen for the detents as you shift it. That should tell you if you are OK. I think we decided that as long as you hit the detents you are in gear.

Glad you found the fuel leak. The float bowls are small, so perhaps it couldn't fill them fast enough, and with a low fuel height, you would be lean and low on power.

I can't answer your question on Quick Start.

fp

 

[KYHunter2]

Re: Rebuilding Power Head

Sounds like your going to get it right.

As long as go through the carbs means a thorough cleaning , and rebuild.

As far as link and sync. , do yourself a favor.

After carb rebuild , start from the beginning of the procedure , and go step by step , no deviation.

Any other way , is futile .

ie: just doing this or that , you may think is wrong, and leaving anything else the way it is , was , etc.

You'll save yourself alot of aggrivation, and be sure everything is correct.

And when you do the rest of the idle breakin . ( up to 1500 rpm's ).

What I do is stand , sit, and keep varying the rpm's almost constantly, very short durations at one rpm.

This is just for the idle portion.

After that I dont cruise at the same rpm's for more then 15 - 30 seconds .

Though the changes aren't drastic , just a few hundred rpm's one way or the other, when on plane.

I just try not to come off plane.

And your very welcome.

The carb rebuild and proper link and sync. , may seem like a long job.

But actually a few hours , is all it will take, since the carbs are off.

KYHunter

 

[MASTER Brian]

Re: Rebuilding Power Head

Brian, listen for the detents as you shift it. That should tell you if you are OK. I think we decided that as long as you hit the detents you are in gear.

Glad you found the fuel leak. The float bowls are small, so perhaps it couldn't fill them fast enough, and with a low fuel height, you would be lean and low on power.

I can't answer your question on Quick Start.

fp

Are the detents the clicking? If so, I think I have it. I just hope I don't need to back it off a turn, but if I do, I think I finally have the technique down, so it's not too bad anymore. I just wish they could have buried that shift rod in a little more stuff!!:^

The worst part is I have to have the carbs mounted to know for sure, so I can secrure the cables.

 

[MASTER Brian]

Re: Rebuilding Power Head

KY, I will run through it per the book with the only deviation being using Joe Reeve's method instead of the books for the Maximum spart advance.

Reading through this I am a bit confused on the "Cam Follower Pickup Timing". The part I'm confuse on is the 2nd step which reads, "2. Advance the throttle by moving the throttle control lever until tip of the amplifier begins to move. Remoce the amplifier but do not move the throttle control lever."

What is the amplifier? Maybe it'll be obvious when I am at the boat going through this, but I can't find it in the manual or in the parts catalog, which has been great in helping identify parts. At this point, I don't want to guess!

Oh yeah, what do I use to clean the carbs? Mine are gold and appear to be a cast metal of some sort. I read somewhere on here not to use carb cleaner for some of them. Not sure if that was for mine or not. I have carb cleaner, solvent, WD-40, spray silicone, brake cleaner, and spray and can deep creep. Will any of those work?

 

[funpilot]

Re: Rebuilding Power Head

Brian, I believe the amplifier is a tool you can make, a little alligator clip with a wire soldered to it (or screwed to the end) which you can use to see if the shaft begins to move when the roller comes in contact with the follower. Instead of looking at the shaft and checking for movement on a 1/16 inch radius, you can look at a four or six inch one with the alligator clipped to the shaft.

I have a gallon container of carb cleaning solution with a parts basket from NAPA. The carb cleaner is basically a naptha with some other chemicals. You can soak each carb once you have them apart and then spray some areosol carb cleaner through them followed by dry, compressed air. Remove the welch plugs with a sharp punch before hand so you can get at all the passages. The carb kits will come with new welch plugs, gaskets, o-rings and float needles and seats. Get the kits with floats too.

Stay away from anything too harsh, and silicon, and especially stay away from WD-40 which will leave behind a varnish when it evaporates.

good luck,
fp

 

[MASTER Brian]

Re: Rebuilding Power Head

fp, it looks like you are correct.

I have been using my OMC manual while doing all of this, but they don't go into a lot of depth on some things, such as tools, etc. They take for granted the person using their manual, knows some of this stuff. Anyway, I can't get the shift linkage set right, so I finally decided I'd break into my clymers manual to see if it said anything.

So far, nothing on adjusting that linkage, but they do explain things such as the amplifier, how to make one, and they go into a little more detail on the carbs as well.

It was brought up earlier about the Clymer's not being as good as the OEM, but I'm not sure I'll agree. It may not be as good, but it's definately a very good reference for the person who hasn't done one of these before and doesn't know all the technical stuff. They even went into detail on the rod caps, they suggest using a pick. Wish I had referenced that sooner.

Anyway, thought that should be said in case someone is watching this thread on their own rebuild.