1988 yamaha 150 v6 outboard rpms drops and mph too

[tony_jatz]

i keep having problems with the rpms droping.i can only get up to 4000 to 3900 rpms .when i gun the gas the miles go up to 34 mph then they drop to 28 and 29 .i have done so much to this motor and still cant get to go faster . does anyone know what the rpms are suppose to be ?i need help !!!

 

[99yam40]

Re: 1988 yamaha 150 v6 outboard rpms drops and mph too

Has this boat and motor ever run properly?
Does the motor have a model #?
What all have you done to it so far?

 

[Silvertip]

Re: 1988 yamaha 150 v6 outboard rpms drops and mph too

Should run 5500 rpm. Have you verified that the engine is actually running on all six cylinders? Did you pull the plugs and take a look at them? Good spark on all six cylinders? What type of boat is this engine installed on? What is the current prop pitch?? Did this engine ever run correctly or did you buy it this way??? Have you done a compression check??? Are the butterflies in the carbs opening fully. Should be perfectly horizontal in the carb throat. If not, link & sync needs to be done.

 

[seahorse5]

Re: 1988 yamaha 150 v6 outboard rpms drops and mph too

i keep having problems with the rpms droping.i can only get up to 4000 to 3900 rpms .when i gun the gas the miles go up to 34 mph then they drop to 28 and 29 .i have done so much to this motor and still cant get to go faster . does anyone know what the rpms are suppose to be ?i need help !!!

You have to troubleshoot for the basics or enlist the services of a trained tech. If it is a common carburetor restriction problem, you could be looking to buy new pistons if you keep running it. Those older carbs had a blind passageway between the fuel inlet and the needle and seats. Debris from disintegrating steel screws inside the fuel pump can float around in there and restrict the fuel flow. There is a service procedure that shows where and how to machine and tap an access port to clean out the cavity. A trained tech in Yamahas should know this.