Yamaha pro v problems

So I need some help with my 97 Yamaha 150 pro v. It is on a 18 ft bassboat. Before the beginning of my problems I could run 63mph. The boat started running poorly, first only getting to about 50mph and it had a hard time getting on plane, and then a few outings later it started stuttering at wot. So I took the boat to the shop.

The shop said it was the fuel pumps and replaced them. While in the shop I also had them install upgraded cylinder heads and a larger exhaust tuner. The stuttering went away but I still had poor top end power and it still has a hard time getting on plane.

A few more outings later it started using a lot of oil. I pulled the plugs and all but one are oil fouled.

So where do I start? I've got some ideas, my first being a compression check.

Re: Yamaha pro v problems

The exhaust tuner is restricted for a reason and increasing the exhaust volume works in reverse by reducing power.

Re: Yamaha pro v problems

I would have got the motor to run properly stock first before trying to modify it just to make sure the modifying or a different problem was the cause of your problem.
I would think more fuel was needed with the extra breathing to increase any power or HP

Re: Yamaha pro v problems

That makes sense, I certainly put too much confidence in my mechanic.

Why would it be using so much oil though. I need to do the math and fiqure out my ratio. I'm adding about a gallon every time I fill up about 25 gallons or so.

Re: Yamaha pro v problems

possibly not adjusted properly, linkage came loose, or leak in oil pump o-rings

Re: Yamaha pro v problems

Did a compression check because I just wanted to know...........starting cylinder 1 to 6.........136,136,134,137,126,130. I did it with all the plugs pulled, throttle wide open, engine warm, and ignition disengaged. The motor has not been run much this winter. Per the manual compression should be 108, but I do have some upgraded heads.

Next I took a look at the carbs. I started the engine and looked down the throat of the carbs. Keep in mind my big problem here is a lack of power getting on plane and at wot. I have also found the cylinder 3 plug not fouled, generally looking cleaner then the others. Snapping the throttle all the main nozzles throw fuel into the motor leaving the throttle blades wet for a few seconds except number 3.

So, what I am thinking is this jet is clogged, float not set right, something leaving that cylinder to run lean. What I didn't think to check........is there another explanation.......would it be possible that this cylinder isn't sucking in air like it should? Could it be a reed valve problem?