Engine problem

fisherkb · Posted: Sat May 21, 2016 6:20 pm Post subject: Engine problem

I have a 2003 Yamaha 90. Until recently the engine was running well with no problems. A couple of weeks ago I left my dock and proceeded to get on plane. At around 2500-3000 RPms (just as it was coming up to plane) the motor seemed to rev, lose power and vibrate. I tried once again with the same result. I didn't push it and went back to dock. Today I decided to change props and I was hoping that I had spun the prop. The old prop looked fine and I didn't recall hitting anything. Anyways I went out with the changed prop and the engine acted the same. It vibrated and seems to lose power when I tried to plane. I have to pull my boat out tomorrow. I guess I need to take it to the shop. Any thoughts on what might be the problem? Thanks in advance.

Karl

starcrafttom · Posted: Sat May 21, 2016 6:36 pm Post subject:

Well it sounds like a power problem and power is created by mixing fuel and air. I would say that you are having one of the other cut off. Most likely your fuel supply has air coming in and you are missing on one or more cylinders. Can you swap out the fuel lines from the tank to the motor? That is were I would start. Also check your air supply. Even if its only been a week since you used the boat last, thats all the bugs need to build a nest in you intake. Pull the air filter off and check it. I have a mouse that fills the air cleaner on my riding lawnmower with seed every winter.

thataway · Posted: Sat May 21, 2016 8:15 pm Post subject:

First to look at is the fuel filters --racor or Sierra before the engine, or the water / fuel separator on the engine. There may be two filters on the engine.

Fuel pump, ignition and other causes are a bit less likely. If the fuel filters are OK, then check back and we can go down the line.

ssobol · Posted: Sat May 21, 2016 8:33 pm Post subject:

I had a similar problem with my Honda BF90D. I took it out and it would not get above the mid 3K rpms. After about a day and a half the problem went away and hasn't returned (knock wood!). I haven't ever figured out what the problem was.

I didn't do anything to fix/troubleshoot the problem.

fisherkb · Posted: Sat May 21, 2016 9:31 pm Post subject:

All,

Thanks a lot. I will check the filters and fuel lines once I get the boat back home. I really appreciate the advice.

Karl

fisherkb · Posted: Sat May 21, 2016 10:23 pm Post subject:

All,

Thanks a lot. I will check the filters and fuel lines once I get the boat back home. I really appreciate the advice.

Karl

South of Heaven · Posted: Sat May 21, 2016 11:08 pm Post subject:

Subscribed. I have a 2003 Yamaha F80. Hope you figure it out and get back on the water ASAP!

dutch123 · Posted: Mon May 23, 2016 1:42 am Post subject:

Have you ever set your tps? I recently had a problem with my f80 and it seemed like fuel related problems when in fact the tps( throttle position sensor ) was out of adjustment. Yours should be the same as mine, .732 volts + or-.014 of a volt at 800rpm take your reading from the black and pink wire on the tps wire harness.