Hi guys,
Been a while and with the help and advice from members on here i eventually got the motors rebuilt and back into boat. (Searay 340 Sundancer)
Whilst the last 12 months motors have been running quit nicely, i ran into an issue a couple of weeks back.
I will be clear as to what i was doing in case it has any bearing on the problem. I was towing my wave runner for most of the weekend, (only 8 knots or so)
But on the way home for speed i detached the ski and throttled up and Starboard side motor would smoothly go up in rpm to approx 3200 rpm with boat planning nicely.
Then without warning die, as in rpm falls fast and i would back off throttle to 1000 to 1500 rpm and stays running. Within 30 seconds i could throttle back up and back onto plane.
And again would last about a minute or 2 then die down.
My first thought is fuel in the rail being used before electric fuel pump can keep up with it. So dodgy pump? (Cool Fuel type)
I would love to here from anybody who maybe knows what is causing this. Maybe its electrical.
One last thing, when diagnosing some things,(this is Port motor) i noticed when i turn port motor off there is a electric motor hum/noise that runs for say 10 seconds then goes off. I don't get this from Starboard motor.
Both fuel pumps do initial charge when keys are switched on. They sound the same as they always have.
Thank you for any help in advance.

You will need to rent or buy a fuel pressure gauge and connect it to the shrader valve to see if fuel is the problem. If it is then you have a one way valve on the fuel tank that could be clogged, fuel pump going, clogged fuel filter, or possible leak.

is this a cool fuel or vst style? I had the pump switch on and off for me before after I replace my top end and it wind up being the connector on the vst was needing attention. There are two metal prongs inside that had flared out from disconnecting it.

Check fuel hose from tank to pump for softness. Had one would suck shut after couple minutes could restart and repeat.

Hi Cableguy
Its Cool fuel.

The only way you will determine if its fuel or not is to go to Autozone and rent a Fuel pressure gauge. Its easy to hook up and you will know if its fuel or not. You fuel pressure will drop before the engine reacts letting you know it is fuel related. If not then you know youll be looking for something else.

buy a fuel pressure gauge its a must have tool as often the pressure is to high or way to high killing pumps i have seen a few over 100 when the regulator gets plugged

engine serial numbers knowing this info also can direct what the correct fuel pressure should be for starters.

Thanks for all replies, this gives me some things to work with.
i am purchasing a Scintex Fuel consumption / monitor that can connect to 2 motors and tells me constant fuel pressure, consumption, litres per hour, and fuel remaining in tanks.
So this will verify pressure for me, will let you know the outcome.
Thanks again.