99 3.1l ox66 wont rev (what am i not thinking of here)

[rjcamel2355]

Hey folks, I have a 1999 3.1l 200hp ox66 engine. A little back story, boat ran last year but a little rough, pulled the kids on the tube fine. Decided to do the LP delete, first time out would surge at mid throttle or under, wide open was okay, but it's cold out so didn't trim up or stay in it long. Figured the surging was a fuel line or air leak in a line. So I replaced it all, tried it out today and experiencing more problems.

Problem: Engine will not rev over 1200-1400rpms in forward. The engine will rev perfectly fine in REVERSE, OR NEUTRAL. I know neutral means nothing, but it will rev fine in reverse under load, strapped to the trailer. It will not rev up in forward, just bogs, fuel pressure at rail reads steady and needle doesn't bounce. It will rev fine out of the water in forward gear on the hose (yes I know this means nothing, but scratching my head on what else to try).

1. Fuel pressure is 35-38PSI and stays steady on the gauge at idle, and under all throttle ranges.
2. Compression is even 100-105ish on my china gauge on all 6.
3. All fuel filters are clean (vst, regulator, and water sep filter).
4. Have tried a remote tank.
5. Replaced all fuel lines from tank to engine.
6. Checked o2 and Barbel, both clean.
7. New spark plugs, cleaned plug boots.
8. Cleaned every ground and added die electric.
9. Did the LP delete with a carter fuel pump and relay, using the hp pump connections to trigger the Carter pump along with the hp pump.
10. I have tried diaconnecting the shift interruption switch.
11. I have tried disconnecting the yellow wire under the ecu. The buzzer does work for overheat and low oil.
12. I have set the tps at .52 with throttle plates closed.
13. Injectors were Cleaned about 2 years ago.
14. Fresh oil and fuel in the tanks

 

[99yam40]

have you monitored spark timing to make sure it is advancing properly?

 

[rjcamel2355]

have you monitored spark timing to make sure it is advancing properly?

No sir, I haven't. Im leaning towards a timing/spark issue though.

I haven't disconnected the O2, to see if it would rev up (I know keep it under 4000rpms).

It's just really strange to me that itll rev fine in reverse, but not forward.

 

[99yam40]

reverse does not load it up as much as forward is my only thought on that.

and a lot can happen in 2 years on the injectors

 

[rjcamel2355]

reverse does not load it up as much as forward is my only thought on that.

and a lot can happen in 2 years on the injectors

Less load in reverse than in forward was not something I thought of or considered. Just assumed since the prop was submerged and loaded it would be the same. Rev in reverse would hit 5k quick and easy.

Forward I could hold it wide open, fuel pressure steady around 35psi, but rpm wouldn't get over maybe 1400 tops.

Absolutely on the injectors, ill pull them and have them cleaned/tested....... id be completely happy if that solves the issue. Just not sure if load and fuel flow would be that different between forward and reverse.

........ill take any tips and try them all though.

 

[racerone]

???----In reverse there would be lots of exhaust in the water and thus less load !

 

[rjcamel2355]

???----In reverse there would be lots of exhaust in the water and thus less load !

That's the only thing that makes a lick of sense to me.

Exhaust pushing water away from the prop thus decreasing load and allowing it to rev.

I plan to:
1. Swap the old LP pumps back on and see if anything at all changes.
2. Disconnect the o2 plug to see if it changes anything (wont go over 4000rpms)
3. Yank the injectors out and send them off