Outboard Help (almost duck related)

Bill Burruss

Bill Burruss

Well-known member
Hi,
Hope season is going well for all. I've had some outboard problems that have slowed me down and would like to see what the mechanics out there think. Last season I thought I was having some overheating problems with my 2004 2-stroke 25 hp Yamaha (posted about it) and thought a new impeller and thermostat fixed it. The boat sat since end of season until early October, when I pulled it out and started it w/muffs. It ran fine and the tell-tale had water, so I took it out pre-season scouting. About 3/4 miles from the ramp it seemed to overheat again (engine reved down, and when I tried to restart immediately, felt tight) and a friend towed me back to the ramp. At home I took off the thermostat housing and lower unit, and flushed the engine both directions- no debris and good flow. Compression was 105psi top, 110psi bottom.Took it out again, and again it seemed to overheat and was hard to pull right after shutting down. No friends around this time, so I let it cool and puttered back to the ramp. Back at home, checked compression, which was now 55 psi top, 110 bottom- big sad face. Popped the cylinder head hoping for a blown head gasket, but found the top cylinder in serious trouble. There was no obvious damage to the head gasket or signs of leakage.


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However, I think the bottom cylinder looks fine- you can even see the factory cross-hatch.


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Called a reputable outboard shop, and the mechanic told me I was looking a $1000 repair (heat would have warped both cylinders, requiring boring/oversized pistons in both). This engine has 2 carbs (one per cylinder), and he told me the most likely cause was a gummed up carb causing a lean condition and overheat. I'm not an expert, but I have seen a gummed up lawnmower carb and I do not think either carb looked bad. This is the first time either have been off the engine, and pic is of the upper. The only deposits I could find were on that little piller in the bowl and under that black plug in the body (low speed jet is just above it, but was not clogged or did not appear to be restricted):


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Anyhow, my REAL question is, does anyone have any thoughts on the cause of the damage? In my rush to get the BB2 back in action (and hopefully not a rush to failure), I bought a new factory power head and carb kit (for a tad less than the marina estimate). I figure for the money I get a new un-salt touched block and all new moving parts, and that I can still salvage some of the season.


I've soaked the carbs in Berryman dip- "the good stuff" (sure hope so- could not find the previous brand of carb dip I bought that had a liquid layer on top to keep the aggressive solvent below from evaporating; hope the EPA did not get that, too, as that stuff WORKED). Will be putting new seals, floats, and float valves in them.


Fuel for the engine has been "by the owners manual" (Yamalube premix at 25:1 for break in, 100:1 since), with the exception that I almost always add some SeaFoam. Guess it is possible the carb gummed and the seafoam dissolved it before I disassembled the carbs, but that sees unlikely in my view. Every 2-stroke (motorcycle) I've seen destroyed was from screwing up the oil. Don't think that is the case here as I am meticulous about it, plus, it should have effected both cylinders.


Sorry for the long post, but would appreciate any thoughts as I am getting ready to install the new power head and would hate to ruin it (an not sure my wife would be as understanding). Really like the old Yamaha 2-stroke on the BB2 and hope to keep this one going for a long time.


Thanks,
Bill


ps- got this in the right forum now!
 
Even though you had flow while running in the yard, the heads could have still been be fowled up with debris/corrosion & but not showing under no load.

Had a Yami 90 hp on our small patrol boat that did the same thing yours did.

Sounds like you eventually knocked most of the gunk out but the damage was already done.

Have you tried it out since purchasing the new parts???

Also, have you checked thoroughly for any cracks in the heads & piston walls???

Will also cause this type of problems.

Just a suggestion, try running a bit more oil in your fuel with a set of hotter plugs.

They will burn up the extra oil & still over lube the engine.

This is what I did on our replacement motor & ran it for (2500) twenty-five hundred hours before replacing it again.

Plugs are cheaper to replace than an engine!!!
 
One other suggestion.

Put a Racor type water/fuel separator on the system if you don't already have one.

Buy the type with the pee-cock bowl on the bottom & drain it after each trip or two.

Also, to prevent new salt buildup in the heads, flush the motor religiously after each trip using fresh water & Dawn dishing washing soap.

With todays fuels, it only takes (1) one drop of water settling in the piston rings can score a piston.

It's amazing how water will condensate in places while the engine sits during the off season.

If you don't use the boat during the off season, I would strongly use the recommended "fogging" spray from the factory.

After the season end, remove the plugs & fog the cylinders as recommended.

Store the engine in a level/down position to keep all seals well lubricated.

This is a big mistake many o/b owners neglect to do & it causes premature seal deterioration.

The best "off season" maintenance tip I can give is to start the engine @ least one a month to get everything lubed properly.

Good Luck!!!
 
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Bill, Two quick thoughts and I will be back later to take a closer look. 1. Forget about the 100/1 and mix 50/1, OMC flirted with the 100/1 and dropped it like a bad habit. 2. When running on the hose it does not verify the water pump is good, you are pushing water through the system with city water pressure. If it was an overheat the top cylinder will be a bit worse but both cylinders will be damaged. If it was a carb problem it will just be one cyl. Got to run now but will be back later.
P.S. 3/4 mile is not enough running to sieze from running lean unless you were running flat out and even then I ?
When all is said and done I think you might have had the perfect storm of conditions. Maybe your gas mix had separated and running 100/1 wasn't enough to keep the parts slipping past each other.
ALSO a compression test on a two stroke doesn't give an accurate test of the condition of the engine. A leakdown test is what really tells the story. You hold the engine from turning and feed compressed air through a fitting in the sparkplug hole. If the rings hold the pressure all is well, if not well you know the rest. When a water pump is turned dry the little rubber arms of the impeller grab ahold of the housing and tear off. It doesn't take but a few turns of a dry water pump to tear it up.
A few random thoughts, hope they help.
 
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I personally don't like the 100/1 mixture. Had a friend with one and he ran into problems also. We adjusted it to 60-70/1 and ran really well. Just check your plugs every once in a while. Keep an eye on the water flow as we usually run really shallow waters and pick up alot of sand. Try to run the motor to flush out after running shallow.
Safe boating, wear your preserver... It's getting cold out there....
 
I know that Yamaha was the last to be able to sell the 2 strokes, owing to the move to 100:1 mix to satisfy the EPA regs change in 2005, and then even that change was not sufficient for the 2010 EPA changes. I have a 2009 Yamaha 2 stroke, and my manual says 100:1, but I mix 50:1 and sleep better! I do add all the additives, both the fuel stabilizer and ring stuff from Yamaha, and then add Starton and SeaFoam too! Way overkill I suspect, but maybe cheap insurance? I don't keep the gas form more than a couple months.... if I don't use it up, then I use it in my truck.
 
I missed you ran 100-1 on the oil.

Try 60-1 & the next hotter plugs.

I would suspect it was either water in the cylinder or crud in the heads that caused the problem.
 
All,
Thanks for the ideas, but suspect I found the culprit. Just got the powerhead off and noticed a small, rusty deck screw protruding from the tube that connects the water pump to the engine block. The head of the screw is almost the diameter of the tube and would have been a major obstruction. Arrggg.


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Somewhat relieved to have a smoking gun and confidence that the root of the problem is fixed. Not sure how the screw got there, but I feel like a surgeon who left a sponge in the patient. There is no way the screw slipped through the pickup grate on the foot, so the only explanation I can figure is that somehow it got knocked/fell into the water pump system when I had the foot off for some other purpose.

Thanks for the help.
Now to make sure there is nothing else in the tube and hopefully get the carb linkage back together correctly.




-Bill
 
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Somewhat relieved to have a smoking gun and confidence that the root of the problem is fixed. Not sure how the screw got there, but I feel like a surgeon who left a sponge in the patient. There is no way the screw slipped through the pickup grate on the foot, so the only explanation I can figure is that somehow it got knocked/fell into the water pump system when I had the foot off for some other purpose.
Click to expand...


Bill

Glad you were able to establish a probable cause and effect. That is always a good thing. Sorry you came to the conclusion as to WHO the likely culprit was. Don't you just hate it when no matter how you try to spin it,,,,,,,,,,, it always ends up pointing at you? :>) :>)
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That will do it, I hate it when you never find the reason for failure, doesn't happen often but it does happen. Good CSI work, glad you stuck with it. BTW your old power head has some value still. Just sayin.
 
Tom,
Thanks for the help.
Seems some of the gaskets and bolts appear to have white sealant on them that have a smell that reminds me of Teflon pipe sealant. Do you know if that is what they use at the factory? I may pick up some before reassembling.
Also, I did try to do a leakdown test on the engine. Not sure I ever got good results. Used a Harbor Freight special with success on an old 4-stroke motorcycle this summer, but it is a lot harder to keep a 2-stroke outboard TDC to get a good reading!
-Bill
 
Not sure what Yamaha uses, check with a dealer. I am much more of an OMC guy, they are cheaper and I have a bunch of them. Good Luck & thanks for letting us know how it turned out.
 
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