1997 370 Sundancer 7.4 Engine Problem

[Barry340]

Hi Everyone-


I recently purchased a 1997 370 Sundancer. Thank you to everyone that previously answered questions I submitted. the answers were very helpful! This is a great website. I am having an engine problem. and I was wondering, if anyone has run into to this before

• When I purchased the boat, had the engines checked out with an engine surveyor, and all results were within all specs.
• Upon picking it up, during a 3 hour run in 4 foot seas, near the end of trip the Starboard Engine's RPMS started to arc wildly from the 3200 I was at to about 1500 as if it was starving for fuel. Slowed it down and tried bringing it up on plane, but could only run at 2000 RPM for the balance of the trip
• Thought it was water in the tank, so I added dry gas, and changed the fuel filter on the bulkhead and on the engine. Checked the screens on the fuelp pump and were clear. No change
• Filled the tank up with fuel (non-ethanol) with no improvement. Tried running off Port Tank. No improvement.
• Mechanic looked at it and said distributor caps and rotors needed replacement. Did that and boat ran great. So we planned a trip with a 3 hour run each way. 20 kot wind and rough heading to destimation, and calm on way back. No problem.
• Went to use it again, and problem returned. Mechanic checked at dock with Mercruiser machine. No errors.
• My mechanic worked for Sea Ray and said the 370's had a fuel feed problem when built, due to excessive fuel line run. They corrected with the addition of in line fuel pump boosters. We tried bypassing the fuel tank valve and shortening the run to the inline pump. No improvement.
• My next step is to sea trial it with the mechanic and the Mercruiser Diagnostic tool hooked up. The problem appears when I am trying to get on plane and the fuel demand is at its highest.

Anyone ever had this problem? Any suggestions? Any insight would be greatly appreciated. Thanks.

BARRY340

 

[FireIsland1]

If you think it is fuel related. start by testing fuel delivery to the rail. If your engine is a mpi like mine it will probably use a cool fuel system. Check to see you have proper fuel flow and pressure. The fuel pump is under the right side motor mount. you could easily swap the hole system from one engine to the other, Take off the cooling lines and the 2 fuel lines at the filter. Two very tight 9/16" nuts hold the unit to the block. The unit will come out in one piece.

 

[Barry340]

Hi Fire Island-

Thanks for the tip. You are correct that it was fuel related. My mechanic and I took it out for a sea trial. Once I put the engines under load the fuel pressure dropped like a rock. We ruled out fuel by switching to the other tank. We were left with decision to replace the fuel pump on the engine, the inline booster feed pump or both.

He had an inline booster pump on the shelf, so that is what we decided to do. With the new inline pump, it solved the problem and the pressure is higher than the port engine. Taking the boat to Captiva for the weekend, so I should have enough of a run to determine if that is the total fix for the problem.

Thanks for your help again!!

Barry340