Z200 hpdi

[Dave Blaber]

Good day my one motor fluctuates rpm when trying to increase the rpm motor will loose rpm then rev up again almost as if there is fuel starvation, I have replaced, pressure regulator, both up lift fuel pumps,o rings, filters and cleaned vapor chamber is there something I have missed, thanks

[rodbolt17]

you can toss parts at it all day long, and there are a lot of parts on that engine.
both medium and high pressure fuel rails need to be monitored at the problem RPM and load.
the YDS software will record the last 13 min of engine runtime when save is hit.

[Dave Blaber]

Thanks for that I am going to replace both motors , as the other motor gave me just as much trouble befor I managed to find the problem, being a high pressure hose. I have had many Yamaha motors during my boating career, but these motors are the worst , thanks for all your help, Dave

[rodbolt17]

the Z motors may or may not have been a good idea.
the biggest problem was lack of dealership training on maintaning and trouble shooting them.
most techs dont have the advantage of having spent 6 years in the navys advanced electronics program as a CIWS tech.