Need HELP... Motor is cutting out
 

I have a 1991 Powerquest Enticer with twin 454 330hp motors. The Port side keeps cutting out at W.O.T. it looses power after about 4-5 seconds wide open.

Heres what I have done:
1. Rebuilt both carbs and switched side when I reinstalled.
2. Replaced Fuel pump on Port Side. Starts quicker but still cuts out.
3. Had it out tonight and thought I would check for arcing on spark plug wires. Found Port side coil wire would arc when grounded. Switched it with the STBD took it out, STBD is fine and PORT still cuts out.

Now the motors run great as long as you are not wide open.

Not sure where to go from here and I hate changing parts for no reason what so ever. Any suggestions would be great at this point.

Thanks in advance.

bump

Just went thru working all the snakes out of my rebuilts. You switched the carbs from side to side to confirm that carb rebuild is not the problem, correct? have all your gaskets under the carbs?(i had one sucking air and wasn't torqued on all four corners). You aren't bumping your rev limiter by chance? the rev limiter doesn't cut the ignition completely off. It eases out and will make you think something is wrong. Thats what my thunderbolt V's did on only one engine side. I am only familar with the TB V. Which ignition do you have?

Make sure all plug wires in proper firing order and boots are snugged. It has to be fuel or spark related as to what you are tracing now. the TB V ignition modules can become cracked with age and temperature, maybe check for that. Just ideas to look at that I have seen

Make sure you don't have a rubber fuel line on that motor that has gone soft and is collapsing on you. Did you swap coils or just coil wires? Pull the cap and make sure the inside isn't carbon-tracked around the terminals. While the cap is off, make sure the advance weights aren't all rusty and easily open out.

Good point. What RPM are you turning on that motor when it starts to cut out. Could be as easy as hitting the limiter.

fuel filter is another one that can impede fuel flow after the pump.

It sounds like a broken valve spring to m. Remove the valve covers to inspect.

Check the anti-siphon valves that go in the fuel tank pick up mine clogged up with junk a few years ago, and engine would run great up to about 4000k than start surge and fall back.

Does it happen at WOT at lower rpms too ? or at a certain rpm ?

Just trying to see if fuel issue when secondaries are open when engine trying to make most power or if it is at same rpm but not throttle position and more likely ignition / valvetrain.

Oh, and when you say 'cut out' does the engine die ? Start misfiring and losing hp ? Or no misfiring noises but losing hp ?

Ok, I will do my best to cover all questions asked on this one:

Carbs have been rebuilt and I switched them from side to side, problem stays on the port motor even with switch over.

I know the ingnition is thunderbolt, not sure if it is 4 or 5 though, will check.

There is no rubber fuel line on this motor.

The motor starts to cut out at 4000rpm, when I say "cut out" it is not dying, just starts to lose power and if you don't back the throttle down soon enough it will eventually fall on its face and shutdown. If you catch the cutting out early enough you can back it down give it a few pumps and maintain as long as you do not stuff it back to WOT.

Fuel filters have been changed.

Anti-siphon valve, should be working if boat spits fuel when filling up tank, which it does currently.

I will be up there on Tuesday and will swap coils from side to side and replace the one bad ignition wire. I will also inspect the wire, points, cap and rotor. I may even take a few pics if something looks wrong.

THANKS TO EVERYONE for all your help and suggestions. I will report back with my findings soon.

That's an issue of your fuel tank vent or fill tube. Usually caused by bends and or horizontal sections on either.

Typically caused by fill tube not vertical enough in spots, thus flowing fuel slower than gasline dispenser.

If you vent is restricted, this will cause fuel flow issues to your motor(s).

Splash back has nothing to do with anitsiphon valve in the fuel line fron tank to motor(s).

Saw on your other post that you got the fuel pump installed correctly, did that solve the wot issue?

Negitive. It runs the same as it did before with the old fuel pump.

Water seperator filter. More then likely water...

I think you have a fuel delivery problem from the tank to the pump. Seems like it is running outta fuel on the top end. Put a 5 gallon can in the bilge (bungie it in nice) with a makeshift fuel line going directly to the pump....then run the boat. I bet it will run fine with that setup. You probably have a problem with the pickup in the tank sir. :drink:

+1

Agree separate your problems - motor side or fuel tank issue side. Use a 5 gallon remote gas tank with a 3/8 new fuel line . The ones that small outboard motors use and do not forget to vent that remote tank to full open position.

We also like using inline a primer bulb 3/8 - the same as outboard engines use to see sometimes by squeezing it if there is a fuel pressure issue but that only works with 2 people in the boat and if there is not too much fuel restriction. I would also hook a fuel pressure gauge up to see what your pressures are. Good luck.

swap fuel lines from each engine and see if the problem follows the fuel line.

I will try the remote fuel cell and see what happens.

I replaced all the fuel lines from the filter to the engine for good measure, and I saw one had a small kink in it.

Will post results.

You have hard line from the tank to the fuel filter housing?

I will have to check.

Well everyone, thank you for all your help.
The problem was the good old anit-siphon valve. When I took it out it appeared to have paper towel residue in it. I clean it out, reinstalled, and now WOT is no problem. Wish I would have know about that from the begining. At least now I know my whole fuel system is in perfect running order.

Thanks again!!!!!!:lolhit:

Wished you would have known about it in the beginning ? This guy suggested that to you the same day...the 6th post down. Good call johnny b good. :drink: