johnson 150 Low Rpm

[qwest]

Hi,

I have a 96 ocean runner 150 that I just water tested this weekend and had some trouble with. motor will start and stay idling out of water all day. In water it will fire right up but only idle for a few minutes then cut off, usually when I give throttle then come off it will shut. If I shift quickly and put it into reverse it will stay running, but won't go past 1500/2000 rpm. I can hear it try to pick up but then it stops. Although, if I put it in neutral it will rev well past 2000rpm.

Ive had some fuel delivery issues with it and want to try external tank next time. Just wondering if this definitely sounds like a carburetor/ fuel delivery problem or if I should start somewhere else. Ive seen online that the 90s johnson have some plastic parts in the fuel system that are known to warp so im thinking that could also be an issue

Motor sat for the past year or 2 and I have not cleaned carbs since I bought it in the winter.

Any insight will help

 

[Chris1956]

Gee, the main jets are real easy to clean. Why not start there. If they are clogged, imagine how clogged the much smaller idle passages are.

Idle passages are located in the throttle bodies, BTW.

 

[racerone]

Check the SHIFT SWITCH on the motor linkages.----Motor may be running on 3 cylinders.-----And a GOLDEN RULE with these motors is that carburetors must be confirmed clean.----No guessing here.-----A restricted carburetor means less fuel and less oil going in.----Damage to pistons may occur.

 

[qwest]

ok, carburetors themselves are confirmed clean. just took off and double checked/cleaned all 6. no visible gunk in any. All gaskets looked clean and I also put some silicon over the metal ball at the bottom of the bowls which I read sometimes leak. Although I did notice some warping on the bottom 2 carburetors on both sides of the motor, didn't realize it is all plastic.

where is the shift switch located?

going to check spark tomorrow to verify that isn't the issue.

 

[ct1762@gmail.com]

these 60 degree motors do not like a bad OMS pump diaphragm. they can do some strange things. ditto for the optical sensor/pack combo. Ive had a few that seemed to be fuel related, but was ignition.