90 etlh stalling around 2500-3000 rpm

[TownsendsFJR1300]

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....

I would use pre-mix initially till you know the oil pump is working.

Thus should help (especially the last post):

http://www.yamahaoutboardparts.com/f...r-th26862.html


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[99yam40]

yea I not sure either how to pull a piston out without pulling the power head and splitting the crankcase myself.
unless there is a different way to get to the rod bolts that I have not seen

[TownsendsFJR1300]

yea I not sure either how to pull a piston out without pulling the power head and splitting the crankcase myself.
unless there is a different way to get to the rod bolts that I have not seen

Remove the reed valve plate to access the crankshaft, lower rods..

Unbolt the lower rod half (a rag to catch any debris would be good to put underneath in the block). Then simply push the piston / rod out thru the top.

It's un-like yours where the rod is NOT removable (without a press and the crankshaft yanked). The crank stays in place, the engine still bolted to the mid section.


Basically, (room permitting), reaching thru the reed holes, remove the two rod nuts/bolts, then yank the assembly:
http://www.boats.net/parts/search/Ya...DER/parts.html



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[99yam40]

learned something new on those old 2 strokes with rod caps

can you get to all 3 rods well?

[TownsendsFJR1300]

learned something new on those old 2 strokes with rod caps

can you get to all 3 rods well?

I don't know how much room is there but should be (as the crankcase volume is as small as possible). Just need to sneak a socket in there, crankshaft / rod is right there (at the bottom of the stroke).

For each cylinder / other pistons, you'd have to go thru the appropriate reed assembly.

[99yam40]

I have no trust in should be.

But I would give it a try if I had the motor and problem.

not sure it would go back together well that way, but who knows, it may

[Idlewildman]

Update

I went to the lake today with 6 gallons of premix and the motor did pretty well considering. It was too rough to really get on it but I was able to make a couple passes at 3500 rpms. I got home and checked compression, its was 90, 109, 115. I know there is some damage to the top cylinder but is it possible that she will run in this condition with the un-even compression? I am going to borrow a buddy's bore scope to see if I can inspect the cylinder walls. Could it just be a blown head gasket? Sorry for all the questions but my knowledge is limited in this area, I know what I know about outboards from reading this forum, Thanks for all the help!

[TownsendsFJR1300]

IMO, not likely it ran that good with a blown head gasket.

No overheating (water temp). You can check your spark plugs to see if the "bad" cylinder plug looks different from the rest.

A leak down test on that cylinder would SHOW if the head gasket is blown/leaking.

90 psi IS lower than the rest BUT you still have a decent amount of compression there. It's NOT like the cylinder is dead. It is working.

Not 100%, but neither are the rest.

If the spark plug looks good, I'd run it normally and see how she does..

Or attempt a tear down for a bunch of $ and time for a motor that may not be worth it..