1987 Yamaha Pro V 150 Stalling

[jwharp]

I am running a 1987 Yamaha Pro V 150 hp.

I have 2 issues and they may be related.

Issue # 1. To get to and from “open water” I must drive via “no wake zone” for about 1 mile. After a short while the engine starts to feel and sound like it is not firing on all 6 cylinders. Once you can increase speed and plane it runs just like new.

Issue # 2. When docking and making a slow approach to a dock it stalls/dies/stops. Or when you change gears from forward to reverse it stalls/dies/stops.

Would appreciate your thoughts as to the potential cause(s) and suggested fixes. Thank you.

 

[jwharp]

I am running a 1987 Yamaha Pro V 150 hp.

I have 2 issues and they may be related.

Issue # 1. To get to and from “open water” I must drive via “no wake zone” for about 1 mile. After a short while the engine starts to feel and sound like it is not firing on all 6 cylinders. Once you can increase speed and plane it runs just like new.

Issue # 2. When docking and making a slow approach to a dock it stalls/dies/stops. Or when you change gears from forward to reverse it stalls/dies/stops.

Would appreciate your thoughts as to the potential cause(s) and suggested fixes. Thank you.

Does anyone have thoughts on these issues? Would appreciate some input. Thank you.

 

[99yam40]

have you checked or replaced the lift pumps?
sounds like they are not keeping up at low RPM.
sucking air at line or filter connections could be another cause

 

[jwharp]

have you checked or replaced the lift pumps?
sounds like they are not keeping up at low RPM.
sucking air at line or filter connections could be another cause

I appreciate your feedback. By Lift Pumps are you referring to the Fuel Pumps? If so, yes I have replaced BOTH Fuel Pumps. If the engine was sucking air in the lower RPM range, would sucking air be an even greater problem in the higher RPMs? Not having any issues in the higher RPM range. If sucking air is the issue how would I test? Do you think it could be ONE of the 3 Carburetors? Each Carb is a dual Nikki carb feeding 2 cylinders of the 6. If so how would you isolate to test which is the problem? Again I value your feedback. Thank you.

 

[99yam40]

I would think that if there is a small air leak on the suction side of the pumps it might cause a problem like you are seeing at low RPM, but at higher RPM the pumps can pump more fuel to keep up.

I have read placing a clear piece of tubing in the system might show some air bubbles instead of pure liquid fuel if that was a problem

 

[jwharp]

I would think that if there is a small air leak on the suction side of the pumps it might cause a problem like you are seeing at low RPM, but at higher RPM the pumps can pump more fuel to keep up.

I have read placing a clear piece of tubing in the system might show some air bubbles instead of pure liquid fuel if that was a problem

Thank you. Boat is currently in storage. Waiting for the ice to go. Hopefully I will get to work on it soon.