Engine missing on top end.

[alamuchee]

Engine is a 325 indmar in a 2006 Supra Launch 21V. Out of the hole is great....¾ throttle is great..Doesn't miss a lick when riding or pulling...it only does it when I go to 100% throttle or reaches 3500rpms....it starts missing a little like small spurts of no fuel or fire. I replaced the plugs and wires and it did not do the trick. I was gonna change the fuel filter next and then the fuel pump if this doesn't work.... Any ideas before I start getting to deep?

[michael hunter]

Check your fuel pressure at when its acting up.

[Indiana Rob]

I have been having a similar problem this year.
Took boat out this PM with great water conditions.
Ran for about 5-10 minutes at roughly 20 mph then lost power I stopped and idled For 1 minute then boat ran fine for next 5 minutes back to shore.
Things I noticed:
Tach no longer working

Oil gauge high?
Idle 20
Roughly 10mph. 40
Roughly 15mph. 60
Roughly 25mph. 70
Gauge goes up to 80

So far this summer we have
-Replaced plugs
-Fuel filter
-Fuel pump
-Cleaned out the water in take filter
-Repositioned the water in take filter as it was upside down
-had to replace the water/exhaust hose

[secondsupra2004]

I have been having a similar problem this year.
Took boat out this PM with great water conditions.
Ran for about 5-10 minutes at roughly 20 mph then lost power I stopped and idled For 1 minute then boat ran fine for next 5 minutes back to shore.
Things I noticed:
Tach no longer working

Oil gauge high?
Idle 20
Roughly 10mph. 40
Roughly 15mph. 60
Roughly 25mph. 70
Gauge goes up to 80

So far this summer we have
-Replaced plugs
-Fuel filter
-Fuel pump
-Cleaned out the water in take filter
-Repositioned the water in take filter as it was upside down
-had to replace the water/exhaust hose

What year/make boat? Carb, TBI or MPI engine? Indmar or PCM?
First guess would be fuel related. If its not sputtering or backfiring I wouldn't think ignition. Not sure what's going on with your oil pressure. You could buy an inexpensive pressure gauge and screw it right in where the sending unit goes to see if it duplicates what your dash gauge shows.

[Indiana Rob]

What year/make boat? Carb, TBI or MPI engine? Indmar or PCM?
First guess would be fuel related. If its not sputtering or backfiring I wouldn't think ignition. Not sure what's going on with your oil pressure. You could buy an inexpensive pressure gauge and screw it right in where the sending unit goes to see if it duplicates what your dash gauge shows.

2001 Supra Legacy
350 Indmar EFI

[secondsupra2004]

You can pick up a cheap fuel pressure gauge with a schrader valve fitting and check your fuel pressure while your running. That way you don't replace a good pump.
Fuel pressure on a TBI system is 28-32 PSI, and 42-60 I believe on the MPI. My TBI checked right at 30 PSI when it was running.

[alamuchee]

What year/make boat? Carb, TBI or MPI engine? Indmar or PCM?
First guess would be fuel related. If its not sputtering or backfiring I wouldn't think ignition. Not sure what's going on with your oil pressure. You could buy an inexpensive pressure gauge and screw it right in where the sending unit goes to see if it duplicates what your dash gauge shows.

This is what all I've done with zero change...

New Plugs...Wires...Distributor...Rotor..Fuel Pump...Filter...Air Filter...Still doing the same ...I keep reading and now seeing possibly throttle position sensor...possibly ICM or ECM.... The boat runs like showroom floor up to 4000rpms....If I can't figure it out I'm gonna run it to end of season and then have it plugged up...but I thought for sure what I've done would have some sort of impact....kinda why I'm thinking and reading more along the lines of a sensor or electronic part.....

And it's 325 Indmar Assault EFI...