'94 120 hp will not go above 3000 rpm

[bhowell1]

Re: '94 120 hp will not go above 3000 rpm

Hi K9hunter....did you figure out what the 'switch' was? My 97 merc 40, 4 cyl behaves the same way...seems to run on 2-3 cyl...low power, won't hit top RPM, then will suddenly 'kick in' and run great (normal) until shut off...next time it's run, its back to low power mode???

 

[k9hunter]

Re: '94 120 hp will not go above 3000 rpm

bhowell1....no i have not yet. i did find a leak on 1 of the 4 carbs where a plate and gasket was not tightend and sealing properly. i tightened the 4 screws and sealed this on 3 of the 4 carbs(could not get to 1 while mounted). This was done prior to my last trip out Friday afternoon. It did not fix the problem. I am pulling all 4 carbs. in the morning to see if there is "crud" in the bowls that is temporarily clogging the high speed oriface. (its a stretch). hopefully someone out here will have had or seen this before and can give advise. Once and if I find out I will definately pass it on to you, please if you hear somethign on your end, let me know as well. thanks

 

[jonesg]

Re: '94 120 hp will not go above 3000 rpm

Swap the weal coil with one of the strong ones, see if the problem follows the coil, if so ....you found it.
Inspect coil when removed, look for small cracks, if cracked its no good.
They tend to fail as the engine heats up too.

 

[k9hunter]

Re: '94 120 hp will not go above 3000 rpm

did the coil swap test already. had a new coil, replaced the weak one w/ it, as well swapped all other coils still weak on #3 cyl. found stator to be bad and replaced as well replaced timer base. have very good spark on all 4 now. motor runs great at idle, and it seems once it runs for about 10 - 15 it gets full throttle and can get all rpm's up to 5500 or so. also as previously mentioned, tested quickstart circuit and over temp. all check out ok.

 

[k9hunter]

Re: '94 120 hp will not go above 3000 rpm

after cleaning carb bowls and adjusted the floats just alittle high, went to lake today and all went well. Boat immediately jumped up to max rpm planed out and lasted the entire trip. so far so good, hope al my "troubles" are over. thanks to everyones help and suggestions.

 

[k9hunter]

Re: '94 120 hp will not go above 3000 rpm

problem..... ultimately neglect. internal combustion engines as I am sure most know require compression, fire, and fuel. compression - all cyls check very good 138 - 142 psi. well within the 5 - 10% within each other range; no compression issues. fire - plate popped out on stator rubbing flywheel, coil on stator shorted, copper wires more than likely internally broken. also powerpak voltage on #1 and 3 cyl low, timer base although passed all electrical checks replaced due to swollen wires and pins falling out of connector. additionally had to rewire most of the main wire harness, but that was done last yr as when you would touch them, they would fall apart - due to spraying entire powerhead w/ wd40 by previous owner. fuel - rebuilt all carbs and fuel pump in spring. once got good fire adjusted floats to allow more fuel at higher rpms where demand is higher.

is it "fixed" now, I still say no. need to complete a link and sync but at least now it will idle and run, where as before engine would not idle unless above 1000 rpm. once it runs consistant, makes easier to do the final adjustments.