Expert: Jeff Grigg - 2/12/2008

Question
QUESTION: I have a problem with my Yamaha 115.every time i take the boat out it will start and idle fine leaving the dock we get to a buoy tie off.sit for a couple then go to leave the boat will only rev to about 10-1100 and bog out kinda like not enough fuel getting to carb just changed the fuel pump last night because it was loosing prim to the ball.carbs were rebuilt about 6 months ago,from what the org owner says.the boat sat after the carbs were done.i took them off and opened them up took out the floats and cleaned everything with carb cleaner.basicly cant figure out why its doing this wife refuses to go out anymore.and i think ur going to tell me to rebuild the carbs

ANSWER: You could have a fuel problem, check to see if you have an anti-siphon valve in the hose barb from the tank, if so remove it. You also need to do a check of the ignition system. You could have a coil or the stator breaking down after running due to a heat problem. If the carbs are clean I see no reason to go back in unless they have been sitting for months or you re-used gaskets, which you should never do. Let me know.
Jeff

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QUESTION: for some odd reason it only happens when the is a load on the prop but if its in neutral it will rev as high as i want it.a friend of mine said for me to change the fuel and water separator

Answer
Never, EVER rev the motor in neutral. It doesn't tell you a thing and can destroy the engine from not having a load on it.
In the bottom of the float bowl is a high speed jet and a tube which the fuel flows through. If the bowl is clean but the jet isn't the engine won't run right.
If the carbs are not sync'd correctly it too will make the engine run bad.
In your case I would bite the bullet and take the boat to a good shop. If you continue to throw "ideas and parts" at it you will only become frustrated and spend a lot of money uselessly.
I would have the shop do a check of the engine, compression, ignition and timing. Have them check the fuel pressure as well as for vacuum on the fuel lines to the tank. These tests will narrow down where your problem is and then you can have it fixed.
Your wife already doesn't trust what is essentially a good engine.
Jeff