1974 Mercury 65hp - 3cyl - bogs down after 1 min at wot

cchinchak

Cadet
Joined
Mar 20, 2008
Messages
24
I had a marine mechanic clean the carbs, change plugs and do a link and sync. The compression is 118-120 in each cylinder. The boat starts easily, idles great, and runs great a lower speeds. After about 1 minute at WOT the boat bogs down a bit but doesn't quite stall. It goes about 3rd to 1/2 speed and kind of burps or misses every once in awhile. Any ideas what could it could be? It was doing the same thing, but worse, before having the carbs cleaned. What about the fuel pump, bad gas, or distributor? I would like to troubleshoot myself before taking back to the marine mechanic.

Thanks!
 

cchinchak

Cadet
Joined
Mar 20, 2008
Messages
24
Re: 1974 Mercury 65hp - 3cyl - bogs down after 1 min at wot

Update: I replaced the fuel diaphragm and used fresh gas which made it run better, but but still not at full speed with WOT. It does not bog down now at WOT. Also I noticed a leak in my supply line and gas leaking from the bottom of my fuel filter. Both have been fixed. Could this be the cause of not being able to go full speed at WOT? Also, is there anything else I should check before taking it for another test drive?

Thanks for you help!
 

jthompsonff

Recruit
Joined
Jun 3, 2012
Messages
3
Re: 1974 Mercury 65hp - 3cyl - bogs down after 1 min at wot

I have one doing almost the same thing, but then it get's hot. sure it is vaporizing the fuel in the pump as I have notised black sludge build up
 
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