I hate 4 Strokes

[Mumbles]

Has anyone checked the oil level in the crankcase? These motors, along with other four strokes, will let fuel past the rings, diluting the oil which in turn will raise the oil level past the ‘full’ mark on the dipstick. An over filled crankcase can cause running issues, but usually at lower speeds.

The orifices in the carbs are extremely small and will let gas thru but not water. Any contaminant or dirt in the fuel system will affect the motors operation. For example, 40 horse Yamaha four strokes are jetted so lean at the factory for fuel economy and emission control that they tend to stumble at mid throttle and above. If the owner doesn’t want to replace the jets with larger ones, I drill them out slightly to fix this problem. One of the tiny jewellers drills used is good for one, maybe two jets before it needs replacing.

[bullie]

Out here again. I pulled the flywheel to check the key. It has definite creases but was not sheared. When I first looked after removing the flywheel I almost celebrated as the key wasn’t in the crank but, it must have fallen out as I lifted the flywheel. Again, it has definite creases so it may have been a little sloppy in there. But, I have no idea what it looked like originally.

[bullie]

[bullie]

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I assume this needs replaced? Owner says he did hit something hard enough on his last outing with the motor running that it knocked the motor out of the water.]

[bullie]

The oil is over filled too. Owner added too much after I mentioned it was low on the stick.

[fleetwin]

This reminds me of something that happened to a new Evinrude/Suzuki four stroke that had hit something hard and destroyed the gearcase…
Dealer put the gearcase on but engine would not turn over without something clunking in the powerhead….Some of these cranks are pressed together, hitting the obstruction caused the crank to spin out of whack as well..Don’t know how the cranks on your engine are made, may not be an issue, must mentioning it…
In any event, that key is shot. Did the crank come off hard, or easily as if the tapers would not locked together. I would examine the tapers and flywheel/crank tapers carefully. You may also want to pop the cam gear off to ensure it is properly positioned…

[bullie]

quote fleetwin:

This reminds me of something that happened to a new Evinrude/Suzuki four stroke that had hit something hard and destroyed the gearcase…
Dealer put the gearcase on but engine would not turn over without something clunking in the powerhead….Some of these cranks are pressed together, hitting the obstruction caused the crank to spin out of whack as well..Don’t know how the cranks on your engine are made, may not be an issue, must mentioning it…
In any event, that key is shot. Did the crank come off hard, or easily as if the tapers would not locked together. I would examine the tapers and flywheel/crank tapers carefully. You may also want to pop the cam gear off to ensure it is properly positioned…

It did not take a lot to pop the flywheel. Not loose, but it didn’t require very much effort to pop off. And, when it did, like I mentioned above, the key fell out of the slot. For a second I thought it was sheared. I did not look at the flywheel taper but the taper on the crank looked as it should, no damage or corrosion.

[amuller]

In most cases there is no real load on the key after the flywheel is installed. So in a case like this I’d suspect that the surfaces weren’t clean and dry, or the flywheel nut was inadequately tightened. It’s not a bad idea to use some valve grinding compound and lap the crank taper to the flywheel. That will at least tell you if there is full contact….

I’ve read quite a few complaints about the carbs on small 4-stroke outboards and difficulties with clogging. This doesn’t make sense to me: The technology of carburation for 4-stroke engines in this size range is hardly new, and engines on lawn mowers, snow blowers, generators, and suchlike don’t have super-tiny orifices in the carb. This sounds like a design defect to me. What make are the carbs?

Alan

[jeff-register]

Bill,
I agree!

[joesnuffy]

Normally I would say their isn’t a load on the flywheel. If something was struck in the water then their would be a load on the flywheel key that is its job. I think Fleetwin is on to something. The key looks to be partially sheered. Might be a poor torque, dirty surface when mounted, sloppy taper, could be anything everyone has mentioned. I also would check the cam timing as he mentioned just to rule it out or rule it in check compression also bent valve possibly? Something swallowed thru intake manifold? And that was interesting that the crank could be tweaked that might be a final check if all else fails to fix problem. With 2 carbs, new fuel pump, cleaned carb multiple times you could almost rule them out. Since you do have 2 carbs you could try increasing the jet size a tad as Mumbles mentioned. When I would dial my jet ski in I would drill jets then check performance of the jet size and if I went to large solder hole shut then re-drill with the best size that worked then order that size jet and replace with it.

Also interesting about the oil level being to high as Mumbles said. I have a 115hp Yamaha fuel injected 4 stroke on my center console purchased it new. One day me and my Labs were out and went to a buddies dock we all were on 1 side of the boat talking to my buddy the boat was tilted to that side for like 40 minutes or so. When I went to start the engine it smoked like oil smoke. I never did that again. Possibly to much oil some got in the cylinders and caused the partial sheer.

Also that summer I would troll at slow speed for a long time when I would go to take off it would sputter, kick, etc and take a while to get going. I researched it and found out it was the alcohol in the gas. I put Bosch type double electrodes in it and that cured my problem. Here is what they look like. I also put them in my buddies 115hp Mercury 4 stroke his was doing the same thing it fixed it we did that after the dealer couldn’t fix it. When I pulled the motor cover it was the same motor as mine I guess the same folks make them?? You said motor was running right then not running right might be the fuel the bosch double electrode style plugs help/allow the fuel to burn normally with the same burn pattern as-if the alcohol isn’t in the fuel.

https://shop.advanceautoparts.com/p/bos … gQodlZUJ7A

One more thing we winter in Key West on a military base (dry camping no electricity) sometimes we get bad fuel down there and it won’t allow our smaller Honda 4 stroke generators to run correctly. I fix my own generators but some of my neighbors would take theirs to the Honda dealer especially when under warranty. It happens to be a marine honda dealer. First thing they do is check fuel for water if water is in fuel they don’t warranty repair. You might try different fuel if you haven’t already.

hope that helps,
just thinking of what I would check.

Joe

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