[freebird273]

can anyone tell me what is going on with my motor? 1984 merc 90 with switchbox ignition. i have gone thru the ignition system according to the book and everything seems to be in order. on the earmuffs it runs great. starts up and idles perfect. very crisp on the throttle. all timing is set on exact. i shut it off and it starts perfect warm or cold. as soon as we put it in the water we have issues. it will start and stall repedily. goes into gear fine forward or reverse no problem. give it throttle and it falls on its face. it wont rev over 1500rpm. the strange part about it is every once in a while the motor will come up full power and run like no tomorrow up to about 4200rpm. i have even run it for about 45 minutes on plane once power comes on thinking it just needed to clear itself out. im not sure whats goin on here and i dont want to throw parts at it till we get it right. ive tested the stator and it seems to be ok. ive changed the rectifier, but have not put it in the water yet to see what results are. i just dont get why the power comes on sometimes. is something loose that i am over looking? i have the maunal, and it just doesnt give good troubleshooting advise. please help. thanks

[Lone Duck]

Sounds like a fuel problem. Check your tank vent, anti siphon valve , fuel filter, and all connections. Still not right. Check for water or sludge in tank and float bowls.

[gregpro50]

If you have completely ruled out the ignition then it sounds like a fuel problem.

I had something happen to mine that sounded similar to your symptoms and it turned out to be rotten wires on the stator. Make sure your wires are all good.

[keiron49]

my 50hp was the switchbox not firing two cylinders. also have you seen this post http://forums.iboats.com/showthread....45#post1772445 it may help.