2000 Islandia won't go over 10 MPH

[LBrinson35]

I recently had to replace the flywheel on the Mercury 240 powering my 2000 Islandia due to stripped out splines. The powerhead only has 20-30 hours on it and it runs like a sewing machine. Perfect throttle response, decent power but on my test run after installing the new flywheel the boat will not run over 10 MPH. It doesn't matter if your at 2000 or 6000 RPM it stays the same speed. Engine sounds fine, the impeller and wear ring look good so does anybody have an idea before I start tearing into the jet pump? Thanks for your time!

 

[buckeye_paul]

impeller slip?

I recently had to replace the flywheel on the Mercury 240 powering my 2000 Islandia due to stripped out splines. The powerhead only has 20-30 hours on it and it runs like a sewing machine. Perfect throttle response, decent power but on my test run after installing the new flywheel the boat will not run over 10 MPH. It doesn't matter if your at 2000 or 6000 RPM it stays the same speed. Engine sounds fine, the impeller and wear ring look good so does anybody have an idea before I start tearing into the jet pump? Thanks for your time!

I hate to jump in here without being able to give you a good answer but I do troubleshooting for a living so maybe I can help. I'm still very new to jet drives. However, I do have some experience with outboards and autos but I still am not an expert. If your impeller and wear ring look okay but you rev up to 6000 with no thrust, you may have something broken (drive shaft or cam) or your impeller is slipping. I don't know how the impeller is attached to the drive shaft. It might be splined or may have some sort of slip assembly to prevent damage to the drive-train in case of an object getting stuck between the impeller and wear housing. Some outboard propellers have a rubber insert which will allow the drive shaft to continue to turn should the propeller hit something solid. I'm sure someone with a lot more knowledge will be able to help much more than I can. Why did the splines on the flywheel strip out? Good Luck.

 

[Dr Honda]

Buckeye... those were helpful starting points.

So... going from where he started....

The impeller is on splines, and held tight with a nut. Even if the nut came loose... I don't think the splines would strip. But it's somthing that needs looked into.

As long as you are getting full RPM at the engine... we have to assume that it's a pump issue.

1) Have you looked into the grate side of the pump? There could be something stuck in there.
2) Are you sure the reverse bucket is moving up?

If both of these check out... the pump will need to be taken apart to investigate.

 

[LBrinson35]

Paul, the splines on the flywheel were stripped out due to whoever installed the new powerhead in this boat last year didn't torque the nut down properly and it walked itself up the crank. I just started getting into the pump, after removing the ride plate, grate, rudder, nozzle and all that other good stuff I did find a "Big Texas Cinnammon Roll" wrapper between the intake grate and the impeller. Surely that wouldn't have held up progress would it? I also went ahead and started to drain the oil out off the pump but the vent plug off to the side isn't coming out so I'm kind of at a stand still now.