50 HP Force runs better on one cylinder than the other!

[Lenmoy]

This 1989 motor seems to not have the mid and just off idle power than it should have! Just off idle it runs rough and shakes and in mid range before planing off the boat it seems to be weak and perhaps stutter alittle. It does, thought reach 5200 RPM albet perhaps slowly! The compression in both are the same at 135 psi, a spark tester shows good spark at both cylinders, full throttle timing is on at 28 deg. BTC but when I did the spark test I noticed it idled better in one cylinder than the other! New spark plugs in both cylindersl. For what it's worth, the carb is super clean. However, in the carb throat sticks up the nozzle with what looks like another tube inside. This inside tube seems to be not in the center of the outter nozzle but rather to one side. Not sure if this matters. Motor is model 507A9B. Carb is model WI17C. I have on order a set of reeds as well as the recirulating reed. Does anyone have any sugggestions?

Thank you

Len

 

[jerryjerry05]

Re: 50 HP Force runs better on one cylinder than the other!

Plugs burning right??
Check the fuel pump diaphram.
Carb is supposed to be that way.
Weak spark? Change coils around and see if it follows.
Something wrong with the reeds?

 

[Lenmoy]

Re: 50 HP Force runs better on one cylinder than the other!

Plugs burning right??
Check the fuel pump diaphram.
Carb is supposed to be that way.
Weak spark? Change coils around and see if it follows.
Something wrong with the reeds?

Fuel pump screen looks clean but wouldn't the engine not run at all if the diaphram was bad? Spark at first check looked slightly weak on one plug but upon a recheck it looked good. I'll check again and also switch coils. Plug color is little dark and the same in each cylinder. Checked color after some minutes running at idle. Good suggestion re switching out coils that I did not think of. Don't know if reeds are a problem as I have not removed them yet but will when new ones come in. I think if there was a broken one I would have blow back thru the carb which I have not noticed. However, reeds where one of my last resorts so I ordered them anyway!

Thank you for your suggestions. I'll let you know what I find out.

Len

 

[jerryjerry05]

Re: 50 HP Force runs better on one cylinder than the other!

The diaphram could have a small hole allowing it to run and also flood out the cylinder.
I believe the pump operates off the bottom cylinder.Is that the problem cylinder?
Pull the carb and look at the reeds.
Pull the pump and take it apart.
Inside the carb.Look for the tiny holes in the brass tube.They must be clear.
Then the jet.
Auto Zone.They sell a spark checker.$5 It measures the spark.
Hook it up and turn the motor over.The spark should jump 7/16"
Just guessing on the spark.

 

[Lenmoy]

Re: 50 HP Force runs better on one cylinder than the other!

The diaphram could have a small hole allowing it to run and also flood out the cylinder.
I believe the pump operates off the bottom cylinder.Is that the problem cylinder?
Pull the carb and look at the reeds.
Pull the pump and take it apart.
Inside the carb.Look for the tiny holes in the brass tube.They must be clear.
Then the jet.
Auto Zone.They sell a spark checker.$5 It measures the spark.
Hook it up and turn the motor over.The spark should jump 7/16"
Just guessing on the spark.

Thank you. I am pretty sure it is either the coil, trigger (although I'm not sure what that is) or the reeds. It runs better on the bottom cylinder alone and after I switched plugs and leads it still ran rough on the top cylinder alone. As it requires several parts to come off to switch I think it is better to pull the boat out of the water before trying to switch the coils or install the reeds which are on order. I'll pull the boat out in a day or so and follow up with you.

Thanks again for your suggestions

Len