SportJet 120XR2 - lack of performance

[X-17]

Unit sits in a Hydrolift X-17, expected performace is 38 - 40 knots. I only get 31 knots.

Jet pump overhauled for previous owner by reputable local company.

The remote control was incorrectly assembled, fixed. Timing was all over the place, adjusted according to the Mercury service manual. NB WOT timing not checked, spark test unit bought but not yet delivered. Not practical nor safe to test on the water.

Reverse shield adjusted on land per book, but end stops remain to be adjusted.

Goes straight ahead with steering wheel straight, veering increasingly to the left as speed rises. At 30 knots the wheel has to be held more than half a turn right (clockwise) and is heavy to hold.

I will also check plugs, status of carbs unknown.

Any other points to investigate? Any help appreciated.

 

[RedBarron55]

Just tie the boat to the dock. You can go WOT there and set the timing. Make sure you have a safety person at the throttle and use nice strong ropes fore and aft.
To set the idle you need to let the boat run free, again use a safety person to look out and steer while you work.
As far as the speed after you have set the WOT timing etc the question would be what RPM are you turning? Normal RPM would be 4800 - 5000. If you are turning high rpm and the RPM limiter is cutting the engine (rough running at WOT, but smooth at just a little less) then no matter if the pump was overhauled I would take a look at the impeller and wear ring.

 

[X-17]

Well guys, disaster struck before I ever came that far. The reverse shield had been fixed in position with a cowboy solution to end all such. I do not think the repair shop made it but they should never have let the boat out of their doors in that condition. Insurance is coming through on the resultant damage though, and fortunately nobody hurt. The boat made a trip "on the rocks" though.

So caveat emptor, once again it has been proved that "reputable" and "repair shop" does not go together.

 

[X-17]

Right, everything back together now. Insurance paid for boat damage. I bought oversize nylon bushings and turned down to size. Made new pivot bolts for the reverse shield. Put helicoil in the housing where threads for reverse shield pivot bolt were damaged.

At full tilt it pulls 4.750rpm. So that will have to do for now. I think a full rebuild of carbs, new plugs and wires, during winter is on the cards.