1998 5.7 gsi power loss occasionally

[Cpell1984]

Hello folks, I recently picked up my first boat to be powered with a 5.7 gsi TBI engine. I’ve only had it for about a month and a half. When I went to see the boat and test ride it ran great. Came right up on plane no issues. We cruised around for 20-30mins at 3500-4000rpm. I brought the boat home loaded her in the slip. Took the boat out for over 4hrs cruising up and down the river. Running great. Got her up to 4200-4500 for a few seconds 35mph and cruised around most the day at 3000-3500 rpm. Next weekend we take the boat out to the ocean 3 hr boat ride from the slip. Boats running great same thing cruising at 3500rpm 30mph. Once in a while I would feel it drop RPM to around 3000. I would back off slightly and bring it back up. Really quick few seconds. Happened few times. Now this weekend comes.... I start the boat fires right up. Noticed it’s pretty Smokey smells of fuel coming out the exhaust. Put it in neautral give it some good revs seems to not want to idle up for a few tries then it finally revs up but still Smokey. We untie the lines and head out. Boats running good planing right out. Few times had the loss of power quick but was able to bring it right up. About 30 mins later the boat drops down to 2500-3000 rpm and loses plane. Now at 3000 rpm the boat is at 9-10mph. For 2 hrs after this the boat would not go over 9-10mph. Then all the sudden it would kick in 30-35 mph 4000-4200 rpm. Come to no wake zone slow down try to power back up same thing 3000rpm 9-10mph.

Boat has new plugs, wires, cap, rotor, fuel filter, new outdrive, new prop, new shift cables, mid season oil change. Oil is nice and clean, coolant reservoir nice and clean. I don’t understand the loss of power some days and other days runs perfect. Some moment loss of power other times perfect. I’m stumped here. Any help appreciated.

 

[alldodge]

With seeing smoke there is to much fuel. To much fuel in most cases is caused by injectors or fuel pressure. VP operates injectors for the GSI at 29 +/- 2 psi. The low pressure pump should be 8 +/- 4 psi.

Either the injectors fuel pressure is to high or the injectors are failing.

Check fuel pressure at the injectors by placing a adapter Tee in line. See what it is from idle to WOT.

If pressure is within spec then I would send the injectors out to be cleaned and flow tested by a place that deals with amrine injectors.

 

[Cpell1984]

Thanks for the response. I’ll be pulling the boat tomorrow and winterizing next weekend. I’m gonna pull the flame arrestor off tomorrow and check the spray pattern from the TBI

 

[Cpell1984]

Checked spray pattern at dock. Started boat was Smokey and smelled of fuel. Took off spark arrestor and spray pattern looked good at idle. Idled it up check again still looked good. Untied lines boat ran great right up to 3500rpm 26mph planned out. Slow down for no wake zone go to power back up and struggling to go over 3000rpm and 10mph. I back off throttle and ease it on up and it gets to 3500 26mph. Next no wake zone same thing.... and I noticed if i try accelerate quickly it just Boggs right down I have to ease into the throttle to bring it up.

 

[alldodge]

The pattern will look good even if the pressure is higher then required, it will just put more fuel in then needed.

Might be able to rent a fuel pressure gauge at the local auto store, just need a Tee fitting to place inline at the TB