Reply To: Bad reed valves on 1991 15hp ?

[Don]

Well, will try to address this, you have mentioned many issues.  Once you get the engine started, does it seem to run normally (on both cylinders) at the higher RPMs it will run at?  If so, this makes reed valve issues less likely.

Are you sure you cleaned that carb completely?  These carburetors (with the plastic bowl) were noted for problems with the rubber low speed pick up hose that feeds from the plastic main fuel pick up to the brass tube leading to the low speed circuit in the carb.  There is still a chance that even if that hose has been replaced, left over debris from the old crumbling hose has clogged the pick up tube/circuit.

The plastic tops on these carbs are another source of trouble, easily cracked/deformed gaskets, expensive to replace.  So, my money is on the carb being messed up.  Does the fuel pump work OK?  Sometimes, a broken diaphragm can cause fuel to leak directly into the cylinder port and flood one cylinder at low speeds.  But, if this was the cause, usually the fuel pump would be inop as well.

As for your vacuum tests, OMC never published any sort to tests like this for their engines.  I’m guessing they felt the results might vary too much and create more confusion than help.  Chances are good, that you wouldn’t see any vacuum reading at all if one of the reeds was broken/stuck open.

I’m pretty sure you can sneak that intake manifold off there to inspect the reeds without too much fuss, even though the lower pan kind of hides a few of the bolts, the rewind will have to come off as well.  Be sure to order the correct intake gaskets and don’t mix them up.  Do not use sealer on intake gaskets.

You never found the left over pieces of the impeller?  Did you inspect the upper water tube grommets?  These engines are known for constricted upper water tube grommets caused by salt build up when used in salt water.

Finally, I do not recommend using a drill motor to start/crank this engine.  You could end up over torquing, or inadvertently loosening the flywheel nut, which may lead to a sheared flywheel key or distorted flywheel/crankshaft tapers.