idle and wot issues

[rjl1914]

1989 force 125, 18' wellcraft C.C., 17" pitch prop, between 135 and 140 compression on all cylinders, recent decarb,new plugs, clean carbs, good fuel, new fuel line and filter. 2 problems that may be related
With the engine cover off, idles at 1200 rpm. Once I put the cover on the engine idles between 800 and 900 rpm. Slowly loads up, rpm steadily drops and then stalls.
When I test ran the boat 5000rpm and speed of approx 40mph
Can not achieve w.o.t. now, reaches 4,100 rpm and 32 mph
What am I missing?

 

[pnwboat]

Re: idle and wot issues

Check your exhaust boot. Not uncommon for it to leak and fill the area inside the cowl up with exhaust fumes and kill the motor. The exhaust boot directs the exhaust/water out of the two holes on the upper back of the leg.

See item 5 in the diagram below.


http://www.crowleymarine.com/mercury-outboard/parts/1288_120.cfm

Easy to replace. Remove 6 bolts (3 on each side) that go up vertically on the leg cover (item #9). Then there are 6 more (I think) bolts inside the cowling and the lower leg cover comes right off.