Loss of power at full throttle

[Soho.99]

Hi all not sure if there is a thread on this already but have 2000 sportster 1800 jetboat - running fine idle great but a couple of times out on the water when giving it full throttle it seems to not put out ...gets to a certain rev then stays there like at half throttle even when stick is full on... no miss in motor compression tested great changed in line filters and spark plugs fixed prob for about an hour then lost power again it runs on half throttle easy and purrs but won’t get up on the plane ... did have warning signal go off once with continuous beep which suggested cooling... checked intake checked tell tail (not shooting out just a dribble) can’t seem to find any obvious blocks ... did have a hose come off at the t piece and water flooded into the hill when motor was running put hose back on and it stopped but still not got full power.. I know the sensor stops full power to prevent engine damage but can’t find the problem ... any suggestions ???????

 

[Tim75]

STOP running your engine until you find out why you don't have a full stream out the pee hole. It can cost you a piston/rebuild job! $1000-$4000! Typical reason for less than full flow is a bug nest in the hose from pee hole to port cyl. head. I keep the pee hole taped over all the time, except when using the boat. Don't judge flow from pee hole except when you are in the water. Testing on a hose is almost pointless.

These engines like fully charged batteries and properly working charging system. Sounds like your alt. is on its way out. Maybe battery. Maybe both.

Charge the battery overnight. Put VOLTmeter onto battery. Crank engine. Voltage should not go below 10.5V. (I think that is the spec.) Engine running @about 2000 RPM, in the water, voltage should be about 13.4V. One or both may be weak.

What were the numbers on comp. test?

 

[Soho.99]

Compression 120 all round maybe one cylinder 118..

How strong should the flow be out the pee hole when on water?? tested yesterday and was just a dribble at 2000-3000rpm ??

Checked the hose for blockages too.. none

I will check the voltage as the battery was flat when we brought the boat since charged it up but not checked again

Thanks

 

[Soho.99]

So a bad alt or bad battery will cause loss of full power yes????

 

[Dr Honda]

To me... it sounds like you have a few plugs not firing. Pull all 6 and post pictures so I can see the electrodes.

On that note, have you checked the spark with a load?

The beeper can be a few things, but to know... we need to know what engine you have. Post a pic of that too.

And finally... the compression is low. 118/120 is minimal on the engine I suspect you have. My 240 EFI is closer to 145 psi.

 

[Soho.99]

The manual for the motor say compression is normal. Spark is fine . Checked all that. Motor purrs likeca kitten no misses at all not hot either.. We did have to bypass the controller it now starts in gear only with no reverse neutral or forward, as we broke the gear selector handle. Have since fixed that and putting it all back together again. We also noted that the engine power loss happened after we bypassed the gears. ???? Coincidence?? We will find out..