Rebuilding Power Head

[MASTER Brian]

Re: Rebuilding Power Head

Does anyone know of a good parts supplier for these engines? P.H.E. was who I was planning on using as they have an entire kit, but I've tried to call a few times this week and everyone keeps being out to lunch, I leave a message and never get a call back. I'd like to get some stuff ordered, so I can get going on this.<br /><br />The local marine dealer is out of the question at this point, because they don't have a kit and they said parts will be over $2k. P.H.E. has the kit and wants under $1k for it.

 

[Dhadley]

Re: Rebuilding Power Head

Call Kurt or Dan at Mar-Fab at 800-476-1554. They have every possible part you need (and then some) plus they can do the machine work or the complete rebuild. Excellent people and they do great work.

 

[MASTER Brian]

Re: Rebuilding Power Head

Thanks, I'll give them a call!

 

[MASTER Brian]

Re: Rebuilding Power Head

Ok, well I finally got this motor stripped apart and ready to go to the machine shop in the morning. It was definately a ring that let go. It was the top ring on the #5 (?) cylinder that had the issue.

I can't find anything that caused this. All the bearings look to be in good order, of course I will replace all but probably the upper and middle main bearings, unless I find they are worn out. There doesn't appear to be any discoloration anywhere either. The only thing I have found is what appears to have been some carbon buildup around the area where the ring let go. About 1 1/2" of ring is missing along with a pitted head and a slightly grooved cylinder. I'm actually thinking a good honing might fix it.

Everyone says to find the cause, am I missing something or could the carbon buildup have caused this? I plan to have the machine shop give me an opinion as well, but would like more input.

 

[funpilot]

Re: Rebuilding Power Head

Carbon build up can make a ring start to stick, it then rocks in the grove and eventually snaps, sending nasty parts throughout the cylinder and head. Make sure the engine will clean up (your machinist will let you know) and the size he goes to before you order pistons and rings. I like to replace all the pistons and rings when I do a rebuild, regardless of whether the cylinders are honed or actually bored out. My favorite is Wiseco, because they are forged, not cast. Make sure your head is smooth, as it will build up carbon there if there are nicks.

Some causes of carbon build up include not enough cooling on one bank or another due to bad exhaust cover gaskets, failed thermostats (so check them carefully, I use a sauce pan and a thermometer to verify opening), too hot of a plug (only use Champion plugs) lack of maintenance (i.e. not running a decarb every season or 100 hours of use, whichever is more often, I like Seafoam Deep Creep) advanced timing or a dirty carb. Lugging the engine (propped wrong) can also be a problem source, and not using a quality two stroke oil. Those with more wrench experience will likely add or correct some of this.

I think the '86 has a VRO, and if yours does, the VRO unit is pretty reliable, but on your rebuild, you will need to run both the VRO pump (don't forget to squeeze the VRO bulb a few times to fill the pump) AND a 50:1 mix in your FRESH fuel to break in. Follow break in recommendations. I use 3/4 throttle max during the first hour, and no one power setting for more than 5 minutes, and I avoid idling for an extended period. After the first hour, and for the first tank of gas occasional full power can be used, but then give it two minutes of 3/4 power or less to allow for cooling. Check that the VRO is working (it will use some oil) and from there on, you just need to keep things clean inside the engine.

Not an expert, but it works for me...
fp

 

[Dhadley]

Re: Rebuilding Power Head

Were the top rpm's in the low 5000 range? Maybe 5500 or so tops?

 

[MASTER Brian]

Re: Rebuilding Power Head

I have ordered the weisco's 30 over, per the machinist, who won't finish the job until he has the pistons in house, so he can insure a perfect fit.

Thanks for your break-in routine, I'll see how it is compared to the manual. Somewhere I have one from evinrude as well.

Dhadley, I don't know what the rpm's where, but I think you are close!

 

[MASTER Brian]

Re: Rebuilding Power Head

I have been looking into replacing the waterpump. I was told I should do it while I'm repairing the powerhead, because I'm already there, but it looks like I have to pull the entire lower unit in order to replace the pump.

I guess my question is how does doing this now save me any time? The only part that looks to be done is the unhooking of the shift linkage. Am I overlooking something? The water pump seemed to be working fine when the PH went down and the previous owner told me he had, had the entire lower unit rebuilt about 1 1/2 years ago at which time I would figure they would have replaced the pump as well.

Am I crazy if I don't replace it? I have one on order, I don't want to cut corners, but at the same time, I don't want to be down any longer at this point.

 

[MASTER Brian]

Re: Rebuilding Power Head

I think the '86 has a VRO, and if yours does, the VRO unit is pretty reliable, but on your rebuild, you will need to run both the VRO pump (don't forget to squeeze the VRO bulb a few times to fill the pump) AND a 50:1 mix in your FRESH fuel to break in. Follow break in recommendations. I use 3/4 throttle max during the first hour, and no one power setting for more than 5 minutes, and I avoid idling for an extended period. After the first hour, and for the first tank of gas occasional full power can be used, but then give it two minutes of 3/4 power or less to allow for cooling. Check that the VRO is working (it will use some oil) and from there on, you just need to keep things clean inside the engine.

Not an expert, but it works for me...
fp

I thought I had a factory specified break-in procedure somewhere, but of course now that I will be needing it soon, I can't find it. I did however find something that said to premix the first tank, what I couldn't tell is what ratio. It looked like they were saying 100:1, but I don't know if that's figuring 50:1 in the tank and the other 50:1 being made up via the VRO. Any ideas? You state 50:1 in the tank in addition to the VRO.

My next question is approximately how many gallons of fuel should I run through on the break-in? Again they state 1 tank, but tanks vary in size and my boat has 2) 12 gallon tanks.

I thought I read somewhere that break-in was about 10 hours, is that too long??

Thanks...

 

[KYHunter2]

Re: Rebuilding Power Head

!0 hours is the procedure I've allways used .

No problems .

I wouldn't worry about , tearing into the lower unit.

If its been operating correctly, and not leaking.

I'd just drain and refill with new lube.

You may never have any trouble with it.

If a seal begins to leak , etc.

Then you can tackle that job.

Just rebuild powerhead and get back on the water.

A tip I have a vacuum sealer and I save the old , used bags.

Then I seal the various nuts, bolts etc. in a bag.

Labeled , as to where they came from .

There are alot of S/S bolts that are basically the same except for length.

Use the slightly longer bolts in the wrong place, and you'll be looking for them later.

1/4" , can make a big difference. LOL

Just ask my EX. LMAO !!!!

KYHunter d

 

[MASTER Brian]

Re: Rebuilding Power Head

I checked with the previous owner and he didn't know if the water pump had or had not been replaced, but I haven't had any issues yet.

KY, bagging the bolts is exactly what I did. As I tore into one area, I placed the bolts and any smaller pieces, like clamps, etc. in a ziplock bag labeled it and even numbered it based on what step in the book I was on. I also took pics with my digital camera of every tear off that had wires or hoses routed, so I can just pull them up on my laptop in front of me when I start to rebuild it. They should be in the correct order and all.

I'm waiting on the rebuild kit to arrive, but I am curious about gasket sealing. Is there a rule of thumb when to use gasket sealer and when not to? For ski's I've always used Threebond 1211http://www.threebond.co.jp/en/product/series/sealants/1200list.html gasket sealer on pretty much all gaskets and to seal the case halves together.

The kit comes with gasket sealers and crankcase sealer, but I'm not sure if it tells me which gaskets get the sealer and which don't. Maybe the manual will tell me...

 

[wilde1j]

Re: Rebuilding Power Head

If you're getting an OEM manual, it will tell you where to use which sealer.

 

[MASTER Brian]

Re: Rebuilding Power Head

If you're getting an OEM manual, it will tell you where to use which sealer.

I have an OEM manual, I'll look at it and see what it says. So far I've only been through the tear down part and a few other misc things.

Thanks.

 

[MASTER Brian]

Re: Rebuilding Power Head

Ok, I finally got the rebuild kit in and I have the block back from the machine shop.

I now have a few questions.

1) Any good tips/tricks to putting the needle bearings into the piston end of the rod? I know to use grease, but any other tips? My motor doesn't use caged bearings for this.

2) Can marine grease be used in place of OMC Triple -Gaurd grease?

3) The manual says to use an OMC Alignment Fixture to install and torque the screws. Why is this? I know they have jagged edges that need to be perfectly lined up, what does the alignment tool do? If I make 100% certain the caps are on correctly and torque the bolts back and forth, until proper torque is that sufficient? I am concerned, because there is a [colour=red]NOTE: Torquing the screws without OMC Alignment Fixture, or using an incorrect procedure, could cause permanent damage...[/colour]

I also noticed, when accidently looking through the 120, 140, 200-225 rebuild section, they mentioned oiling the cap bolts. Why is that? I would think they would require loctight. It says nothing about either for the XP 150!!

4) What is the purpose of the AMC Locquic Primer? I have the loctight, but not a primer. Do I need to pick up some primer? I've never used that before.

I think that is enough for now, thanks for any info and if you have any other pointers that I might come accross!

 

[MASTER Brian]

Re: Rebuilding Power Head

I thought I would add, in the rebuild kit, I have the following....

Pro Marine Gasket sealer, which I'll use according to manual.

I have needle bearing assembly grease, which I use to install the needle bearings. Can this also be used in place of OMC Triple-Gaurd Grease?

Loctite 518 gasket maker....I'm guessing this is used in place of OMC Gel Seal.

I also have Loctite 271, which is the threadlocker. Do I need a Lozquic Primer as well???

Sorry for all the questions, just don't want to mess this up....

 

[KYHunter2]

Re: Rebuilding Power Head

As far as the triple guard grease , its not the same as assembly grease.

I use any good marine grease as well as triple guard if I have it.



If locktite 518 is an anaerobic sealant ,(dries without the presence of air). I use it for the crankcase halves.

I've used the locktite anerobic , before and its the same as gel seal .

Haven't had a problem , I just can't recall the number on it.

I'd look but its in the shop, not at my home.

I use locktite on most of the bolts, not head bolts .

Nothing on them.

Never used the primer, and haven't had a problem.

I chase the threaded holes and replace or clean up all bolts.

If the gasket sealer is the type with the brush in the lid of the can.

I use it on everything but the crankcase halves.

If you have trouble with the assembly grease, being too runny ,when trying to install needle bearings.

On piston pin end or con rod to crank end .

Vaseline works better, that is if yours are loose, if they're caged no need.

Be sure to get the head gaskets on correctly.

If you don't the cooling passages will be blocked.

 

[Mark42]

Re: Rebuilding Power Head

My OMC manual lists 12 gal of pre mix with VRO before running straight fuel.

I have been throught the break in proceedure twice now. I prefer to be alone in the boat during the first two hours so no one distracts me from paying close attention to the motor's performance and gauges (and sound).

Also not a bad idea to take the boat out empty (no load) so the motor does not have to work hard when running at less than WOT during the first few hours.

When you first take it out, be sure to mark the VRO tank with some masking tape while the boat is on the trailer in a level location. So when you come back you can tell if the level changed. The oil level in the VRO tank goes down so slowly, it is critical to ensure that oil is actually being pumped out of the tank and into the fuel.

The 25:1 mix is not just in case the vro is not working, the motor needs the extra lube during break in for proper ring and bearing seating. So check that the vro bulb stays firm during the first few hours.

 

[MASTER Brian]

Re: Rebuilding Power Head

One thing that still isn't clear is the oil in the tank mix, when using a VRO pump.

I have been hearing 50:1 in the tank, but it looks like the manual is calling for 100:1 fuel/oil mixture in the fuel tank in addition to the VRO system.

Next it says for 1st 5-10 minutes, operate engine at fast idle. I'm taking that to mean, no wake speed.

After that the next hour should be at about 1/2 throttle. Then for the next hour (second hour) 3/4 throttle, both with boat on plane. During the 2nd hour it says to apply full power for about 1-2 minutes at a time going back to 3/4 throttle for cooling.

Then after the 2nd hour up to the next 10 hours, not to appl full-throttle for extended periods.

Does this sound about what all of you would recommend as well?? Which is it....50:1 or 100:1 in addition to VRO pump?

Also, am I correct, not to leave at the same exact throttle position for more than a few minutes at a time during break-in?

One last question...what about using engine pre-lube, like you would use to lube a car engine, while re-building? Or does 2 stroke oil suffice?

 

[KYHunter2]

Re: Rebuilding Power Head

Ive never used anything but 2 cycle oil , and assembly grease.

I brush the pistons , bearings on crankshaft etc. with straight 2 cycle oil while assembling.

Never had any problems at all.

KYHunter

 

[Mark42]

Re: Rebuilding Power Head

Generally OMC wants to mix the gas at 50:1 (same as you would regular pre-mix on motor without vro). Then, assuming the VRO is working, (also giving aprox 50:1 mix) you end up with a 50:2 or 25:1 total mix. That means twice as much oil as normal for additional protection of new rough surfaces (cylinder walls, bearing races, etc) while the parts wear in.

You said the motor is a '86, so I'm sure that the 50:1 premix in addition to running the vro is the way to go.

Also, check with the rebuilder. If you sent the complete power head, then chances are the rebuilder already ran the motor at high idle for 10 minutes on a fixture before you got it to ensure that it will just not "grenade" when you fire it up for the first time.

If you did not send the complete power head, but just the short block for boring and assembly, then it is up to you to ensure that the first 10 minutes are high idle (about 1200 - 1500 rpm) running only do not idle. Again, if you are not sure, ask the rebuilder what he wants you to do to preserve any warranty on the parts and labor they offered.