Help with motor

[IA4PATS]

I bought a boat with a 2003 Yamaha 115 four stroke. It doesn't seem to run very well. I know the gas was pretty old so I sucked that all out and replaced it with added Seafoam. It stills runs kind a bad. I put all the power to it and it doesn't have the power to even get on plane. It seems to rev up good in neutral, but not in gear. Do I need to run it more to get it cleaned out? Also, it has this thing on it. Could this restrict it that much?

[KK]

Check this link out

http://forums.iboats.com/forum/engine-re...adly-above-idle

[Can'tFishEnuf]

I had the same thing happen with my 50 Yamaha. It seemed like the idle was fine, but wouldn't run well under power. It was a bad spark plug. With the motor running, I pulled the spark plug wire on each and would listen if the idle changed, which was pretty obvious. It did change on three of the cylinders, but not the one. I replaced the one bad spark plug and noticed the idle was a little better. I replaced all the plugs after that. It is surprising how well it will idle with only 3 cylinders firing. When pulling the plug wires be careful to touch only the rubber boot or you will get a pretty nasty shock.

[IA4PATS]

Well, I sucked out all the gas and replaced it with new gas and some Cheveron injector cleaner and Seafoam. I also replaced the fuel filter and spark plugs. We took it out this morning. The first couple seconds it ran a little rough and then went pretty good, but not great. Got up on plane, or is it plain... anyway, running about 20mph and 3500 rpms. went for about five minutes and then it started to bog down again. by the time we got back to the dock area I was doing about 6.5 mph at 1800 rpms. It is now parked at a shop.

[Hubcat]

I had similar problem. It turned out be that my motor was sucking air from a bad gas tank, but I had a external gas tank. I assume yours is a internal tank, could still be the problem.

Also another time when my 4 stroke was acting up it was I think the fuel pump. there is high speed and a low speed fuel pump (I think that is what they were called) and one of them went out.