1985 Grand Sport 3400 losing power on starboard engine .

[Grand Sport Guy]

Hello, I'm new here, but I have a few question. I just purchased a 85 grand sport with twin crusader 350's (454). The ignition system has been updated so no points anymore. The starboard engine starts up fine runs and idles with no issue. After a few minutes of being on plain the engine starts to lose power and i can smell fuel. I backnoff the throttles and it continues to idle fine. Go back up to 1500- 2000 rpms with no issues . Anything after that it will start to lose power. One thing I noticed is when I hit the trim tabs I start to lose power also. I'm going to change the fuel filter/water separator and then clean the cap and rotors to start with. Also the boat was in storage for 1 1/2 years prior . The starboard engines battery was weak ( about 4 years old). So I plan on replacing the battery as well. Any other ideas or things to look at?

[LMK]

That fuel smell bothers me in that report. I would spend some time maintaining and checking the fuel system as you have said. Does the same fuel tank supply both motors?
You are correct on replacing the battery but once cranked the alternator should supply voltage.
Have you done plugs on these motors and if so what did they look like?

[Billm]

Do have two gas tanks? If so, try running both engines off port gas tank and see if bad gas is the problem. Stuck Distributor advance weights will present as normal operation below that rpm. Maybe pull the spark plugs to see what they look like. There could be a valve problem.

The trim tabs are curious. They could be just creating more drag when fully down.

[CptBill]

Billm made some good points, another thing to check would be the carb. Sounds to me like it's running rich and that could be the result of the above or it could be the carb itself

[Grand Sport Guy]

It has two tanks , I ran them both off the port tank and still has the same issue. As far as the trim tabs go, it only loses power when I actually hit the trim tabs. When I get down to the water friday morning I'll pull the plugs when I check the rotor and cap. Both tanks also have fresh fuel in them.

[LMK]

I hope those fuel filters solve it, good luck!!!

[Grand Sport Guy]

Things I've found so far, but i haven't verified if its fixed yet. Rubber gasket was missing on water separator/ fuel filter. Fitting for the carb filter was loose and the ground on battery connection was loose.

[Grand Sport Guy]

Issue is still there, going to check the plugs next.

[goodday]

Float probably hanging up while running with angle of boat undercruise in short time, about long enough to run bowel low

[mccarthyej]

@Grand Sport Guy - I had a very similar issue, fuel smell, not getting power at higher RPMs, and eventually the engine would shut down on me. I could bring it back to idle and it would be fine. My advice is to check all of the hard fuel lines. I thought my issue might be the carbs but wanted to start with the fuel pump as it's cheaper to repair. I went to take one of the stainless fuel lines off and it shattered. That explained my fuel smell and the loss of power. When the engine would call for fuel, it essentially was sucking more and more air until the engine would shut down. I don't know of any way to test this though. That's the challenge. For this reason, I will be replacing all (I think there are only 4 or 6) of the hard fuel lines this winter as part of preventative maintenance.