89 blackmax 150 runs poor when cold

[vipertec]

I have a 150 blackmax that runs terrible when running for first 1/2 hour.In neutral i can get high rpms,but when in gear I can barely get 1200 rpm.If I try to throttle more it stalls.As the engine runs(approx. 1/2 hour)the rpms will slowly increase to 1500 then 2000 then eventually will completely clear up and run fine.If i run it within afew hours it will be fine,but let it sit overnight ,then it will run poor.I removed carbs and cleaned,changed fuel filter,fuel in tank,no good.I had this condition for awhile.While on atrip to canada I took to dealer and they said stator was faulty so I replaced with new one last week.Tryed to run boat this morning and still ran poor for awhile until clears up.note:also tryed primer bulb while running to see if it needed fuel and no change.Any help would be great.

 

[CraigC]

Re: 89 blackmax 150 runs poor when cold

I'd start with the basics, you already cleaned carbs, etc. - but I'd check to make sure you have spark on all 6 cyls when engine is cold, run a compression test, then maybe do a link n' sync.
I had a similar problem before with it not wanting to rev up like that, and it turned out that one of the switch boxes was bad, causing spark problems...of course that didn't go away when engine was warm for me, but sometimes it would get better for a little bit, then act up again shortly. Replaced both switch boxes and it was perfect.
Good luck.

 

[vipertec]

Re: 89 blackmax 150 runs poor when cold

I have checked compression previously and all was ok.I am a auto mechanic but not completely familiar with outboards,the switch boxes you talk about,are they the two black plates that the stator terminals attach to?They are stacked on top of each other? also ,what do you mean by link n sync.thank you for the help.

 

[hkeiner]

Re: 89 blackmax 150 runs poor when cold

but not completely familiar with outboards

I would suggest that getting an OEM shop manual for the motor is the first thing to do. Link and sync is a sequence of steps to ensure that the motor is properly set up. All steps are important and each step is dependent on the previous step being done correctly.

Regarding troubleshooting, one thing to do is determine if you are missing a spark on any cylinder while the motor is bogging. You can use an inductive timing light to do this, by seeing if the light strobes while connected to a spark plug wire.