# Yamaha 150 fuel injected four stroke topping out at 3500 RPMS



## Land_locked (Aug 6, 2009)

I have a Triton 2690 with twin Yam 150 four strokes behind her. Recently my port engine has begun to have some power issues. Both engines crank right up and work fine at lower speeds(trolling, maneuvering in the marina\no wake zones) however, when i throttle up the port engine tops out at 3400 or so RPMS @ WOT. My starboard engine winds up to 4800 RPMS(5400 was max RPMS when both engines ran fine, so i account the drop to the added drag from having to make up for the bum engine). If i back off the throttle and jam it forward the engine will rev up to 3800-4000 rpms but would slow down 1000 rpms every four or five seconds until it levels out at 3400. When i run the engine with the cowling(sp?) off the engine kicks and pops and has a slight wobble to it. Both engines run off the some 250 gal. tank. Ran it from Freeport across Chocta. to the pass and back. Engine was solid....just slow. Towards the end of the ride the RPMS began to fall SLOWLY to where the engine topped out at around 3000 and would rev to 3500 or so.

Im thinking of changing water separators\fuel filters and the spark plugs. Any other tips or recommendations? Would be glad ti take someone for a ride or short trip to fish\assess the engine. 

Also, with fuel prices rising, i am beginning to need some crew to split costs. PM me if interested.

Thanks
MF


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## Sequoiha (Sep 28, 2007)

It sounds like a fuel issue, i think you are on the right track with the fuel water seperators, another thing you can try with twin engines is to swap the fuel lines at the seperators and see if the issue follows or stays, also if 5400 was max rpm when they ran fine, this isnt really high enough, these engines operating range is 5000 to 6000, and should be propped to the higher end of the range. i would like to see about 5800 as max rpm, and if you want to run 5400 thats fine, i would be glad to discuss this on the phone if you want to call me, or we could fix it for you as well,,


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## TheCaptKen (Mar 14, 2011)

First you need to change the filter on the high pressure pump on the VST tank then change the filters in the injectors. The injector filters are not hard to change if you know how to do it. We see this all the time and usually the changing the injector filters cures the problem. DO NOT continue to run the engine or you risk leaning out a cylinder and burning a piston.


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## Darrell27 (Jul 18, 2009)

check the check valve in front of the vst ,,,that fixed mine....good luck


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## Sequoiha (Sep 28, 2007)

for you to change the vst filters on a F150 would require him to take the intake manifold off, for most people this is above their level of experience. not saying it his, but most. i dont recommend the general public getting into their vst or injectors, with that said, like capt ken said if you continue to run it with a fuel issue you could lean out the engine and damage it. if the fuel water seperator on the boat and the primary filter on the engine doesnt take care of it, i recommend it being looked at by a professional..


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## Sequoiha (Sep 28, 2007)

TheCaptKen, i would like to know where you are getting injector filters, i have not been able to find any..


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## TheCaptKen (Mar 14, 2011)

There is a site on the internet that one of the Yamaha rep's gave me a while back that you can order them by the bagful. PM sent


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