won't go over 10 mph

[rboppre]

I have two 1996 yamaha waverunner III's. I am having a problem with one of them not going over about 10-15 mph. This is what I have all checked or swapped with my other waverunner: plugs, wires, carberator, checked compression 150 psi on both cylinders, check the thermosensor ( put it in 160 degree water and waited till the continuity went from open to some resistance.), swapped impellers. What am I missing. When I take it out on the lake it will go up to about 10-15 mph (don't have a speedo) with out a problem but that is where it maxes out. The engine runs fine. Out of the water the engine revs fine but as soon as there is a load put on the engine it does this. Any help would be great. Oh yeah and I also removed all the old gas and put fresh gas in.
thanks,
rboppre@netzero.com

[leon phelps]

Re: won't go over 10 mph

COuld be either fuel problem or drive train problem. Look at impeller. Could be bent or rubbing. Carb or fuel pump could be bad and just not getting enough gas to get going.

[randyj]

Re: won't go over 10 mph

I have a similar problem...caused by fouling plug on one cylinder at higher RPM.. when it clears off I can zoom till it oils up again and again starts running slow on only one cylinder...right after new pistons and rings.

[frankey01]

Re: won't go over 10 mph

Have you changed your spark plugs and clipped back your wires?

[rboppre]

Re: won't go over 10 mph

I have changed the plugs and swapped carberators. Also have swapped impeller assemblies. This is why I am stumped. It will go up to 10 mph with no problem but no matter what I do it will not go over 10 mph. any ideas?

[David3aces]

Re: won't go over 10 mph

change out water box...baffles inside come dislocated and then plug up outlet...I have fixed about 1/2 dozen WR3s by doing this....

[rboppre]

Re: won't go over 10 mph

so the water box will get clogged and make the machine not go fast? can you tell by just looking at it when it is out of the ski?

[David3aces]

Re: won't go over 10 mph

sometimes you can shake it and hear the loose baffles...sometimes not....

[surveyguy]

Re: won't go over 10 mph

nope, I bet it's clogged/bad carbs in need of rebuild. On the trailer, it doesn't need much gas to rev-up. On the water (any engine under load) it requires more fuel. I say fuel (pump, carbs, probably not filter or lines, but worth a check)

[rboppre]

Re: won't go over 10 mph

I already swapped carbs with a known good one.

[David3aces]

Re: won't go over 10 mph

on trailer, do both plugs get equally warm after running 15 seconds?...if so try water box....his ski has 1 carb......

[rboppre]

Re: won't go over 10 mph

thanks everyone for all the help. Thank you very much David. It was the water box. I am now relieved that I don't have to think of these waverunners all day long haveing it bug me. thanks again

ryan