1986 Johnsont GT 150

Toallhisdoom

Cadet
Joined
Jun 20, 2015
Messages
27
Model number is J150STLCDC

Bought boat couple years ago. Occasionally it would hesitate on acceleration. Would only run at low rpm for maybe 30 seconds, then would take off.
Went out yesterday. Took boat out for first run after winter up and down the river. Had 1 instance of this. But otherwise was fine. Towards end of day starting giving me issues starting and was smoking A LOT. Put in 1/4 can of seafoam in fuel, and $20 of gas. Went out today and right off the batt it would not accelerate. Idles fine, but anything over like 10% throttle and it starts to bog. Pumping the fuel bulb while under accel made no difference. Came home and checked fuel fitler, bit of dirt in it. Going to replace. Checked spark plugs, they were oil covered and some gunk, wiped them off and they look like new, were replaced end of last season.

Any ideas?
 

Toallhisdoom

Cadet
Joined
Jun 20, 2015
Messages
27
Oh also she tops out at around 45mph. Does that sound right? Its on a 18ft 1987 skeeter starfire with a 3 blade stainless prob.
 

ggodwin

Petty Officer 3rd Class
Joined
Feb 14, 2017
Messages
75
Did all the spark plugs look the same? Specifically the right side vs the left side.
 

Toallhisdoom

Cadet
Joined
Jun 20, 2015
Messages
27
Did all the spark plugs look the same? Specifically the right side vs the left side.

Yes. I ordered a spark tester. And going to rent a compression tester this weekend.

Took her out yesterday. Boggs like crazy until warm. Will put along fine around 1/4throttle until warm then runs fine.

So issue is only when motor is cold!
 

Toallhisdoom

Cadet
Joined
Jun 20, 2015
Messages
27
check your thermostats arent stuck open
1 of the thermostats was stuck open. Pushed closed and tested in a pot of water. Opened but would not close, 2nd closed smoothly.

Ordered 2 new thermostats.

Did spark test, tester bulb lit up for all plugs. Have not got my hands on a compression tester yet. Will try new thermostats and if that does not cure problem it will be on to compression test, and then most likely carbs.
 
Top