Just can't figure it out. HELP!

[metalmash]

The boat is a 2004 Sportster LE DI (951cc)

Boat start and idle perfectly. Out of the water reach max RPM no problems but running a bit rough.
In water, can't get past like 5mph, engine sounds like it miss and cut at like 3500-4000RPM and can't get it higher than that. Can't get the boat on a plane. No audio beeps. One day it worked perfectly, the next day it struggled a lot to get on a plane. Now there is just no way to get it on a plane.

- Brand new wear ring/impeller installed by dealer.
- Got the computer checked for codes, nothing. Dealer said the engine seems to be running good (they did not test the boat in water)
- New rings on pistons, compression is like new.
- New coils installed.
- Changed spark plugs.
- Voltage is OK (14V when started, changed rectifier last year)
- Fuel pressure (tested just before the injectors) is above 100psi.
- RAVE valves cleaned.
- No beeps.

The way I see it, the problem occur when the engine in under load (in the water). Out of the water it runs freely up to max RPM (around 8000). Missfire? Not enough air? Not enough gas? Could the exhaust be clogged? Sensors? (What kind of sensors are in that boat?) Reeds? (what are the wymptoms of bad reeds?)

I have put over 50 hours of work trying to find the problem, I am so desperate Any ideas before I get it back to the dealer? Thanks!

 

[Dr Honda]

First of all... you can't test anything out of the water. Without a load, even the worst engines will rev-up.

OK...

1) I know you said the piston/rings are new... but did you check the compression after the issue started? What you are telling me is very indicative of low compression.

2) Did you check the air system? A leaky air hose will keep the fuel from getting in.

3) Did the shop remove the injectors and check them? (They could be plugged up)

4) Did anyone check the rectifier? When they go bad... they either pass AC or high DC voltage. When that happens... the MPEM and CDI do all kinds of strange things.

 

[metalmash]

First, thanks you for time!

1)Compression before new rings = +/- 105psi. After new rings = 130 psi

2) How do you check the air system? (Not even sure what it is...) Also, if it matters, when started in the water and revvin-up, fuel pressure (tested on the fuel pipe just before the injector 'module' on the engine) is above 100psi which seems perfect to me?

3)No. Could I check that myself? Also would injectors go bad overnight?

4)Well we changed it last year and when it did go bad the engine would not rev-up past 3000RPM, there was a beep every 1 minute and the voltage at the battery was very low at like 11V. None of theses symptoms are appearing now.

The boat running the way it is, if find it weird that the MPEM don't have any codes in it? Also, on the last trip that the boat was running fine, I hit a lot of hard and big waves, and I sometimes wonders if there isn't something that got unplugged or something.... But I doubt it.

 

[budsyboo]

Have you checked the plugs. I had a bad plug once and it did something similar?

 

[metalmash]

Fuel pump was dead. Replaced by the dealer. Boat runs like new again!