Vacuum on carbs 1 & 2 a lot more than 3... What gives?

[Laddies]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

The job requires a special speedy sleeve that is sold by any Mercury dealer, cost is about $25 here's the service bulletin.

 

[honda460ex]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

Thanks a ton Laddies! That gave me the info I needed to search it out. I found a link from another iboats thread thanks to a search on that part number.

http://www.boatpartguys.com/ocart/86349A1

Ordered and hopefully will see it soon! Ordering another water jacket cover too. Got the old one back today and it is to far warped to bring back. Thanks again all, this is why I love this site!

 

[honda460ex]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

Ok all. Looks like my lower seals are working now with the sleeve. But I still have an issue. Carb 3's idle adjustment is having no affect on the idle. All the way in or out makes no difference. Carb problem you say, no says I. Have a whole other set I cleaned and bolted on, same issue. (And yes I replaced the gasket and have checked for a vacuum leak around the carb) Swapped carb 2 that was working fine to carb 3's location and you guessed it, same problem. Adjustment does not work. I replaced the reeds a short time ago and have had no luck ever since. Idles a ton better, but this problem with carb three is killing me. Tore it down again today to check the reeds and make sure they were still ok. They look good. But, I got an idea of what my problem may be. When I disassembled the reed blocks to replace reeds I didn't put them back in the same position that they came apart (1, 2, 3). Could it be possible that this reed block was wore bad enough from being in another location that a vacuum leak problem between cylinders 5 and 6 could cause this? Thoughts? This motor is driving me nuts. All new gaskets, seals, electrical, etc... etc... etc... It's had it all.

 

[honda460ex]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?



Here is the best pictures my camera would let me take of the reed block on the bottom two cylinders.

 

[CharlieB]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

What could be some possible causes for this issue? It's an '83 115hp inline 6. ................................ You can place your hand over carb 3 and the motor will keep on running for a little while before it will finally die down and start dripping fuel out of the front of the carb.. The carb IS getting fuel. I really believe the lack of vacuum though is causing it to not pull enough fuel and hence the miss at idle. Spark plug 5 is slightly wet. Not much, but some. Spark plug 6 barely has any fuel on it at all. Almost totally dry..............................................

When you had the crank out to get at the reeds, did you mic the cyls and pistons?

two stokes wear the cyls more at the middle of the cyl around the ports, they can loose ring seal in the lower half and reduce crankcase vacuum yet still have upper cyl seal and compression.

 

[honda460ex]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

Thanks Charlie B, hadn't thought of that. I did not mic them. I do have it apart at the moment though so I will have to check it before putting it back together. I found a used set of reed blocks that are supposedly in good shape along with new needle bearings for the two main center bearings and a new lower crankshaft bearing. Going to replace all of them because I noticed that I do have a little play in each of them except the upper. The miss did go away when I swapped carbs, but the adjustment still wouldn't work. And when you would place your hand over carb 3 this last time around it would cause the motor to die fairly quick. That old carb had to have something in those idle ports that I just couldn't seem to get out. But, this last time running I had no miss. So like you said, I guess it could be in the cylinder and I will check it out. Thanks for the help! I'll post back when I know!

 

[oldman570]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

How dose the bleed hose and fittings look on the block lower end? If one of the hoses leaking or a fitting is cracked it might be sucking air there and cause low vacum in the crankcase? Just a thought.
Oldman570

 

[asm_]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

sub to this thread.

I too have a similar problem a year ago. 1982 In-line 6 with top two carbs doing all the work. In my case, my did work in gear up until 1800RPM. I have spent so much time on it that I finally decided to just leave it for while.

 

[honda460ex]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

Well guys, I am officially going nuts and officially out of ideas. I need help in the worst way on this one. Mic-ed the cylinders this last time apart and found no difference really all the way up and down inside the lower two cylinders from all different angles. Changed out the reed blocks with some used ones that were in much better shape and kept the reeds on them because they seemed to be in really good shape. Replaced the lower and upper one way valves and hose that sits on the side of the powerhead. Replaced lower crankshaft seals once again and replaced with three new ones all in the same way they had originally been. All back together and yet again carb threes idle adjustment does nothing. I even clamped off the enricher valve and tested it to make sure it wasn't leaking down excess fuel with no luck. I checked the mating surface of carb 3 and the block and found both to have a perfectly level surface. When I pulled the plugs on cylinders 5 and 6 after letting it run on muffs for a while I found both to have some fuel on them but not significantly wet. You can pull plug wires on cylinders 5 or 6 one at a time with little effect on the motors idle when on muffs. Checked spark on both plugs once again and both are firing a good gap. I am stumped all and chasing my tale on this one. Lol, and I thought rebuilding the boats transom, stringers, and floor this last year was a pain! ANY HELP GREATLY APPRECIATED! Or any knowledge of anyone in the Northern Kentucky / Greater Cincinnati area that is a VERY GOOD outboard mechanic who DOESN'T CHARGE A FORTUNE and is willing to let me watch and learn on this one...

 

[honda460ex]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

I am leaning towards a vacuum leak somewhere but have yet to find one even with WD-40. Does anyone also know if it possible to do a leak down test on this outboard and if so where would you get adapters and such to do so?

 

[Chris1956]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

Have you checked the cylinder balance hoses? OK, an '83 should have sidebowl carbs, with backdraft jets. You have cleaned the idle restrictor tube and the rest of the idle circuit? There are some pin holes in the carb throat, that need to be clean. The holes in the main nozzle also need to be clean. Sometimes if you try to remove the idle restrictor, a piece of brass will fall into it. Did you seal the brass plugs over the idle restrictor? Check the screen under the brass elbow on the bottom carb cover? They can get clogged.

 

[honda460ex]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

Thanks Chris. I have done all of that though. I even replaced the carbs with another set of identical carbs with the same jet sizes, same housing, and same class of carbs. I even took one form the old set that I knew was working properly, just to see, and replaced it with carb 3 with the same results. I spoke with a good friend of mine who has his own boring and honing shop for small engines who has been doing it for longer than I have been alive and he led me to a certified outboard mechanic in my area who just recently opened his own shop. My friend Dave has been doing a lot of jetski cylinders and such for him lately and talked highly of him. Lol, it's good to have friends... Dave told me to call him and explain my problems and if this guy Paule wouldn't give me an answer to call him back and he would call him and get the answer. According to this guy Paule I could have very well lost most of my secondary compression and the primary compression could be masking it by still showing 120 lbs. He says of course the secondary compression will draw the fuel into the case and it makes sense that it is pulling just enough fuel to run but not run right. I think what led to this initially was when my lower crankshaft seal blew. I was on Lake Cumberland and ran it a good 5 miles before I shut it down. My rpms had dropped around 1-1,500 and I was loaded with people and gear so I kept it on plane to get back to the ramp. After that it didn't have the power to get up on plane again. Worked on the carbs thinking I had a clog and being 3 hours from home on a trip i had no tools or parts to get in deep. Tested it out a day or two later with a lighter load and milked it to get on plane finally. Ran it a total of probably 14-15 miles that day not realizing the whole time my lower crankshaft seals were pretty well gone, therefore robbing cylinders 5 and 6 of fuel and oil. That's what I am leaning to believe now, that I jacked up my lower two cylinders. Not positive and probably won't know for a while because I just found a powerhead that's the exact same year as mine with good compression and supposedly runs for just a pinch more in price than what it is going to cost me to buy two new pistons and bore and hone the lower cylinders. Going to throw the new powerhead on and save up some play money to totally rebuild the other old '83 for a future need.

 

[asm_]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

I hear what the certified mech. is saying. But, I don't see how that provided any new info than what we already know. Since the the third carb is not drawing enough air into the crank case to pull the fuel out of carb, we already know there is a leak some where in the cylinder 5/6's crank case. The the million question is: where is the leak.

If the cylinder compression checked out ok, than the piston/ring/cylinder can't be that wore to cause a leak. I don't buy the theory that the leak is occurring at the piston ring. My guess is, it has to be some where else.

 

[honda460ex]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

I get what you are saying and agree with you, but at this point it is no where to be found and my options have literally ran out. The cylinders 5 and 6 are pulling just enough fuel to fire, but not enough to make any power or to make the idle adjustment effective. I've looked for cracks, sprayed around all gaskets and mating surfaces enough to keep WD-40 in business for a year, replaced and reworked crankshaft seals three times now, checked all surfaces to be sure that they were level and smooth... All except boring and honing cylinders 5 and 6 it has literally been done. The motor has been down since June now and I am not someone to let something rest. My wife has been ready to kill me because I probably have spent most of my waking hours on this motor since June trying everything.

 

[CharlieB]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

That is exactly what I was trying to explain earlier, that two strokes cyls wear most in the area of the ports, the lower half of the cyl can wear such that ring seal in the lower half does not pull full vacuum on the intake to draw a complete intake charge. Also as the piston is still on the down-stroke in the lower cyl half it will not pressurize the crankcase well enough to fully transfer what charge it does have to the upper cyl thru the transfer/intake port.

If you have the motor apart carefully mic the cyl top, again just above and below the ports, then a forth time just above the lower ring wear line. Then determine if or how far out of spec the cyl is and whether reboring will fix your motor.

 

[CharlieB]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

Another thought, is this a switchbox ignition, NOT a distributor, and have you changed the trigger just before all this started?

With the plugs out turn the crank to TDC on #1 and chalk a line on the flywheel, repeat for each cyl.

Run the motor and check your chalk marks with a timing light to ensure that each cyl mark fires in the same position.

My thinking is that #3 trigger may be a few degrees retarded as compared to 1 & 2, which would cause cyl 5 & 6 to be retarded and not pulling full vacuum as they are not loaded as much as the upper cyls.

 

[Laddies]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

On a 83 115 the fuel pump should be on 5 and 6 cyl. so if the pump works the cyls. have base compression and vacuum that leaves the pump with a problem have you removed the pump lines from the pump to check for pressure at idle?

 

[honda460ex]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

I hadn't forgotten what you had said from an earlier post CharlieB. I just hoped it wasn't that. It is a switchbox ignition, not distributor. I replaced the stator after I had my initial problems because I realized the hack job someone had done on it. They had one of the low end windings to fail so they did away with it and the high end winding that was on one powerpack. They then jumped the other high and low end winding off of one powerpack to the other. Then on top of that, the wires leading to the rectifier were burnt up at the base of the stator. It has a new stator, rectifier, and trigger now. I will check what you said out though. Worth a shot.

Laddies, are you saying that the vacuum that makes the fuel pump work is derived only from cylinders 5 and 6 then? Sorry, but I am a little confused by the wording of your post. I have not pulled the fuel lines at idle to check pressure at the pump though. I have cranked it with the top line removed, but never actually checked the pressure. FYI though, I did run to the garage real quick to check and see before I posted this, the fuel pump is actually mounted beside carb 2 and I think I remember the vacuum holes for that run directly into the case. If that's the case then of course my pump is operating on vacuum from cylinders 3 and 4. If incorrect, let me know, I am still learning... Thank you both for the input.

 

[honda460ex]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

On another note, if I do have to tear it down again, my friend who has his own boring and honing shop for small engines said he would be more than happy to mic it for me if I brought it over to him. I trust him a lot more than myself checking it again. He was a machinest for GE Aircraft Engines for many years so he knows the importance of precision. If I haven't figured something out with this thing in a week I guess I'll pull it apart, again, and have him check it. I'll post back results one way or another on it. I'll test the timing of the fire tomorrow night like you said CharlieB and let you know.

 

[Laddies]

Re: Vacuum on carbs 1 & 2 a lot more than 3... What gives?

I don't have a 115 in the shop to look at right now but to my recollection the pump was mounted on the port side of the lower cowl with pulse lines running to 5 and 6 crankcases. There is even a service bulletin out if the engine had fuel problems to put a spring into the lines to keep them from collapsing. You will have to check the routing on your engine to see where the pulse lines are attached, if it is 5 & 6 it would be a easy way to check crankcase pressure