late 80's 70hp idle issue

[stevewabc]

Hello everyone,

I rebuilt this motor last yr (10 hrs on it) and it runs great cold but as soon as it gets warm I want to take a ball bat to it... here is the funny part of this hole thing that drives me nuts. we put the motor on a dyno and it always runs great even after loading it down and working it hard after a hr no issues. Put the boat back in the water and here we go again first start it and runs great.. run around for 30min or so and back to it again will not idle blowing smoke every were, its like its dumping fuel from the crabs but rebuilt them all... hooked them up aligned them by vacuum and the same problem again and again im lost. hope some one here has seen this type of problem before.

I need ideas please...

70HP Yamaha with tilt and oil injected
model #70ETLK

Thank you
Steve

[stevewabc]

What no one has any idea's on what would cause a it to run well on a dyno but flood out on the lake?

[99yam40]

I have no idea what you are calling a dyno for a outboard as I have never delt with one
If you have access to the equipment of this sort for an outboard, I am sure you have all the books on your motor and someone knowledgeable running the equipment. Do they not know what is going on?

Not sure how you used vacuum to adjust the carbs as they do not have any place to hook up the manometers that I know about

[stevewabc]

I have no idea what you are calling a dyno for a outboard as I have never delt with one
If you have access to the equipment of this sort for an outboard, I am sure you have all the books on your motor and someone knowledgeable running the equipment. Do they not know what is going on?

Not sure how you used vacuum to adjust the carbs as they do not have any place to hook up the manometers that I know about

99yam40 ty

this is a dyno image below, when one has no tank this works well... but every time we put this motor on it there is no issues ... (7 times now) how can you fix something that wont act up? this is crazy take it down to the lake with in 30 min max back to not wanting to to run at a idle, it dies and a real pain to get started again.


Thank you for any input on this.

[99yam40]

Looks like a hydrolic pump possibly.
Can the resistance be con*****ed for the proper load on the different motors?
Could the load be different on the dyno and on the lake itself pushing the boat.
How is the motor cooled during these runs on dyno?

Being you motor is a carbed 3 cylinder, maybe the motor is getting hot with the 30 minuet run on lake because of not the same cooling happening.

Exhaust gases getting into water stream to pump or air getting sucked in due to something disturbing water in front of water intake.

Have you looked in the carb throats to see if there is fuel bubbling into the motor when this problem show up