need help, tough one 70hp

[desertratz]

this is a tough one, hopefully someone can help...

1989 johnson tj40tlcem

boat will start and idle fine, will run good for a little while seems like it warms up and starts having the issues.
it will start acting like its running on 2 cylinders instead of the 3, loss of power and eventually will stall. it does this when i slow down. after it stalls its hard to start. to get it to start i have to accelerate the engine to about 3000 rpms and choke it simultaneously.

sometimes it will run great at around 4000 rpms as long as i dont slow down, once i go to idle or slow speed it will stall out.

things i have done:
checked spark ,when it wont start, jumps 7/16 gap
new plugs
new cdi box
carbs cleaned and rebuild
new fuel pump
new fuel tank and lines and primer bulb
ohmed coils
ohmed stator
ohmed timer base

the specs for the timer base are conflicting between the cdi website and the manual i have not sure which are correct.

anyone have any ideas? i am pretty frustrated at this point.

 

[jbuote]

Have you tried connecting a timing light when it starts acting up and seeing if you actually lose spark?
​Just watch for lost flashes..
​Not an expert here, but maybe try that. If you are losing spark then that's a place to start..
If not losing spark, then it's not ignition related I'd think...

Just a thought...

 

[desertratz]

thanks for the reply, jbuote. i was at the lake yesterday and did try this. it seemed to have spark when it would not start. i had flashed while cranking on all 3

 

[boobie]

Squirt some premix in the carb throats once when it does this and see what happens.

 

[oldboat1]

Sounds offhand like a carb problem remains, but try using the bulb to keep it running (tests operation and assembly of the new fuel pump). Simple test, no reason not to try.

Is engine temp normal? somewhere around 120 -- 140F on top of the heads (depends a little on lake temp). Over 160F is too hot. May be one of the motors requiring relocation of the tell-tale.

Check compression.

 

[desertratz]

thanks for the suggestions guys.

boobie, i have tried hitting the choke which squirts fuel directly into the throats when it starts to die and it will make it die instantly.

oldboat, i disconnected the fuel line running to one carb and the pump filled a water bottle full of fuel in a short period of time, so as far as i can tell the pump is working. i also had my brother pump the bulb as we rode around it was soft so i installed a new one but didnt make a difference. new one holds prime. not really sure how to tell if its getting too hot i can put my hand on the thermostat housing for a few seconds without burning it. and i did relocate the tell tale to the top of the exhaust chamber.

i checked the compression with motor cold 105-110 psi per cylinder i should probably recheck it the proper way.