Power Loss Merc 65 hp

[MercMan69]

NEED ADVICE:
I have an old mercury 65 horse engine on a 16' runabout. It runs great out of water, forward and reverse, revs smooth and everything. I took the boat out on the water and it won't rev hardly at all. the boat won't do over 8-10 mph. I have checked spark, fuel and compression... all of which are good. When its in the water it sounds like it "wants" to go, but is holding back... pulsing, but out of the water it screams. When it has a load on it, in the water, it won't go into reverse, it makes a grinding noise. I thought maybe it was over-propped, but the guy who i bought it from says it ran great with that prop. The engine is not charging the battery, could this possibly be a contributing factor or is this an unrelated problem? Can anyone give any advice? Could it possibly be a timing issue?
Thanks!!!

 

[OldMercsRule]

Re: Power Loss Merc 65 hp

Could be lots of things. Sounds like your cables are out of adjustment re: shifting issue. Does the throttle go all the way forward, (as both the shifting and trottle cables could be a problem). I would suspect fuel since spark and compression are good. Does it help if you pump the bulb while underway? Fuel pumps are easy to R & R if you get more power from a bulb squeeze, plugged up carbs are a little more of a job to R & R. Good luck. JR

 

[JimMachinery]

Re: Power Loss Merc 65 hp

If you have a type 1 electrical system, it could be the spring tension on the points (just read that when I was trying to figure out which electrical system my 1967 65 hp inline four has. Good luck!

 

[Windykid]

Re: Power Loss Merc 65 hp

If it's not charging the battery you might want to fix that first.