Top two holes on Force L drive won`t fire.

[Lake Skywalker]

Hi all; Huge problem regarding my 120 Force,I bought this boat and it started right up on the muffs,so far so good,took it out to the lake and when I was at full throttle it was only making like 10 mph.Got it back home,fired it up on the muffs and did a spark plug drop test.That`s when I discovered it was only firing on the bottom two cylinders.I did a compression test and all holes are between 120 and 125 p.s.i. which is not too bad.Did a leak down test they were all good.Put it on a spark tester and they all had great spark.Put a Boroscope in the spark plug holes,pistons, etc. look good.Re-did the top carb,both carbs are getting fuel,but when I put my hand over the top carb intake,it`s barely drawing any air in,I also pulled out the reed plates they are also nice and tight and all there.My buddy who is a marine Mechanic said he`s never seen this issue in 15 yrs of working on boats.I`m stumped,he`s stumped,anyone have any suggestions? Thanks!!

 

[jerryjerry05]

Re: Top two holes on Force L drive won`t fire.

What year?Serial#?
Any water on the plugs?All burning right?
U sure they are getting gas to both carbs?
More later sorry,J

 

[jason32038]

Re: Top two holes on Force L drive won`t fire.

Could be a stator problem on that circuit or a complete failure on the top cd pack which operates spark on cyls. 1+2. You'll never know until you test.

 

[pnwboat]

Re: Top two holes on Force L drive won`t fire.

If the top carb is hardly drawing in any air, I'd take a look at the by-pass cover gaskets for number 1 and 2 cylinders or any open fittings that are on the by-pass covers for those two cylinders.

 

[Lake Skywalker]

Re: Top two holes on Force L drive won`t fire.

Could it be head gasket or exhaust gasket?

 

[Lake Skywalker]

Re: Top two holes on Force L drive won`t fire.

Hi It`s a 1990 (120LD90C) Serial # is 1849,I`m getting great spark to all holes,the Carb bowls are full,When you put your hand over the bottom carb when it`s running it sucks your hand in,when you put your hand over the top carb you can`t feel barely anything.The plugs all look good no water,(or fuel on the top two)

Thanks.