90 etlh stalling around 2500-3000 rpm

[Idlewildman]

I can idle fine, get up on a plane and once the rpms approach 3000 the engine looses powers and kinda bogs down until it finally kills. I try to re crank it and it acts like the battery is near dead (which it isn't). Once I able to get it back running it runs with a dead miss. I can go keep it running at a high idle and the second I put it in gear it kills. Eventually I can keep it running and put it in gear and the miss goes away and everything seems fine..... I try to run it again and the whole thing repeats itself.

I have checked the following:

- Fuel pump is OK, diaphragm is good no leaks
- Checked each cylinder by pulling plug wires while idling, all are firing and appear ok.
- Checked compression all 3 cylinders are 110,112,110
- Installed new plugs
- Fresh gas
- Drained fuel from water separator
- Replaced primer bulb

I am starting to lean toward a rectifier or CDI...

Any help is greatly appreciated!!!!

[robert graham]

Maybe check the battery and connections....maybe a weak battery cell or loose/corroded battery cable?...

[99yam40]

monitor the fuel pressure and vacuum.
that should tell you if it is restricted.
also look for pump sucking air causing motor to running out of fuel.

never mind, sounds like motor is locking up from what your hard spinning over remark

[pstephens46]

Battery thing and cranking has me confused.

Too much fuel?

[99yam40]

sounds like too little fuel causing a piston or something else to bind up the motor
cool down and then move it some and it moves well again

just a thought

[TownsendsFJR1300]

How did you test the battery? Load test?

*How many volts at the battery static, idling, 1,000 RPMs?
How many volts at the battery when CRANKING OVER to start (especially when it acts up)

I suspect cables corroded, not getting a charge to the battery, killing it...

The engine won't run correctly with low voltage....

If the battery is already toast, a new one is needed and again, test voltages..

[Idlewildman]

OK...... I figured it out and lets say its not good news. I was removing the fuel pump one more time to check the diaphragm and the oil lines were kinda in my way. I removed them from the pump to get them out of my way and there it was... WATER in the oil lines! I found that the oil tank cap was cracked and must have let water in to the tank, which in turn got into the carb instead of oil which meant I was running with no lubrication, that explains the engine seizing up and not wanting to crank and when it cooled down it allowed me to crank it. I broke out the compression gauge once I saw this and now the compression is 90, 110,110. I guess it must've scored the cylinder walls? Now I'm wondering if it will run considering I damaged the #1 cylinder. I have no idea what the next step would be to rebuild this thing and considering the age I'm sure I would have a hell of a time with broken bolts.

[TownsendsFJR1300]

You still have a fair amount of compression in the bad cylinder so that's good... It should run, but somewhat rough.

Either scope the cylinder or simply pull the head for an inspection. Go slow, lots of heat, penetrating oil, etc...

I'd fix the obvious(oil, etc), and see how it NOW runs with proper lubrication.
Might be able to squeeze another year or two out of it...

If scored up, with the age, probably not worth the tear down (unless doing the labor yourself)


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[99yam40]

Scott, I am sure you know how running a weedeater with no oil until it dies/locks up does a motor if you have tore many apart.

My exwife and kids did that a time or two.
strange how they did not understand the oil thing.

the motors were never the same.
piston and rings at least if the cylinder can be cleaned up.

to think a little harder, no oil probably got bearings also

[TownsendsFJR1300]

Scott, I am sure you know how running a weedeater with no oil until it dies/locks up does a motor if you have tore many apart.

My exwife and kids did that a time or two.
strange how they did not understand the oil thing.

the motors were never the same.
piston and rings at least if the cylinder can be cleaned up.

to think a little harder, no oil probably got bearings also

Of course its disastrous for an engine to go thru that.

I had a 5.5 Honda horozontal shaft engine that was seized up big time(junk picked-PWer)(did have nasty oil in it). I poured oil down the cylinder, vise grip on the crank (removed the pump). Took a half day but eventually got it to turn over (never pulled the head). Got it running, ran great! Put the pump back on, gave it to my dad a couple years ago. Still runs great...

For the Op, what's the choices?

He can pitch it-easy, expensive..

Fix it, expensive, is it worth it?

Or, with nothing to loose, try running it, see if he can get another season or two out of it...

With the head off, if the cylinder isn't bad, (just rings worn?), perhaps pull that piston, hone the cylinder (if still in spec's), replace piston and rings. No splitting cases.

The engine is a 1987 (from earlier posts) and the head has been removed recently (so access is easily done).

The parts diagram shows a two piece rod assembly:
http://www.boats.net/parts/search/Ya...TON/parts.html

So yanking the piston is very doable W/O pulling the power head.

The parts diagramshows the LOWER & upper rod bearings are caged NEEDLE BEARINGS:
http://www.boats.net/parts/detail/ya...-730V8-00.html

Very likely, the bearings are fine, rings/piston /cylinder, that's the question of the hour..

I'd personally pull the head and look at the cylinder. If not tore up, yank the rod / piston and go from there...


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[99yam40]

I bet that 5.5 Honda motor was not a 2 stroke like his 90 Yamaha is.
no oil running thru the crankcase and maybe a little water instead does not go good on the bearings.

Rod has said in the past oil problems will normally get bearing before the piston.
lean on fuel to air ratio will get a piston 1st.

not sure how he can get to the rod bolts without pulling the power head and splitting the case.

I was suprized to see rod bolts on that old 90

[TownsendsFJR1300]

I bet that 5.5 Honda motor was not a 2 stroke like his 90 Yamaha is.
no oil running thru the crankcase and maybe a little water instead does not go good on the bearings.

Rod has said in the past oil problems will normally get bearing before the piston.
lean on fuel to air ratio will get a piston 1st.

It's a needle bearing, not a solid bearing which will handle more than a "solid material bearing".

The piston / rings / cylinder will seize up before those Needle bearings will..

A partial tear down (at least-if repairing) IS needed to verify the crank, block,etc is serviceable..


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[99yam40]

all the 2 strokes I pulled apart are needle bearings or ball bearings on crank and piston pins.
4 stroke have been Babbitt or solid on crank as you say.

still does not make much difference no oil means bearings get very hot and turn things blue before seizing up, easy to see when taken apart.
they also like to chunk rods or other parts out the side of blocks

as you said aluminum pistons melt before steel but it depends on which gets hotter faster. and if pistons melt I am sure the bearings are not good at that point from no oil

[TownsendsFJR1300]

The piston / rod is coming out anyway for inspection / replacement so the bearing will be accessed.

As long as the crank isn't damaged the bearing rod /can be replaced..

Any updates OP?


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[Idlewildman]

Nothing done yet, I'm still trying to figure out how to prime the oil pump so I can at least get it running to see how she acts and recheck compression. Plus I not sure of the steps you guys are talking about....