97 Force 75 HP fuel delivery question

[badly bent or broke]

I purchased this boat last fall and had problems with it not idling properly. It runs well at other times but sputtered and died with regularity when running at low throttle, less than 2000 rpm. After reading this forum I found out that a rebuild of the fuel pump was probably in order and did that over the winter. On a couple of trial runs in January and February it ran much better at low RPMs and I thought I had the problem licked. Now the problem is back and I am scratching my head and reading this forum to figure out ma solution. It acted like it was starved for fuel or maybe there was water from condensation in the gas. I changed the fuel filter, removed as much old gas as I could from the tank and changed spark plugs but still was experiencing the same problem this week. I thought that air could be leaking around the cable ties that were use as clamps on the fuel lines so I replaced them with hoses clamps and visually inspected the lines for leaks but didn't find any.
Since the fish weren't biting yesterday, I took the cover off and cranked the engine to see if I could see anything obviously wrong. The main thing I noticed was that the fuel filter was never full of fuel as I expected. Shouldn't the fuel pump keep it full when running? After watching it run at different speeds I never saw the fuel filter anywhere near full, much of the time it looked empty with just enough gas passing through to keep it running. Once after it died, I pumped the bulb and noticed gas leaking out of the fuel pump. I checked the screws on the fuel pump and tightened them a little but gas still escapes around the gasket. That gasket must not have been installed properly and is probably causing my problem.
My questions for the experts are?
1) Should the fuel filter run full of fuel?
2) Should I just replace the fuel pump gasket or put in the whole rebuild kit again?
3)Does anyone have anymore insight into this problem?

 

[pnwboat]

Re: 97 Force 75 HP fuel delivery question

Assuming that the fuel filter is between the fuel pump and the carburetors, it should stay pretty much full. At least 3/4 full. The leak at the fuel pump is probably why it isn't staying full. I would suggest that you replace the fuel pump gasket. The leak would also indicate that you aren't pumping gas like it should be. There is a gasket kit that is relatively cheap. If you replace the gasket, take a close look at the sealing surfaces to make sure you don't have any cracks or gouges that may be preventing a seal. There is also a small vacum port underneath the fuel pump on the engine that is sealed by a gasket. It needs to be clear, other wise the fulel pump will not work properly.

You also may want to check the compression. Low compression can cause idling issues too. It also will cause hard starting problems. You didn't mention any starting issues so that may not be a problem. I had a friend that had an older 70 force that was difficult to start and would not idle properly. It turned out he had over-heated the engine and the rings had carboned up so bad they were frozen in the ring grooves on the pistons cuasing low compression. He was reading less than 100LBS of compression in each cylinder. Replaced the rings and the motor started and idled like a champ. It was like it was a different motor.

Carburetors also have an idle mixture adjusment. I would suggest that you get a manual before adjusting the idle mixture. It is possibe to cause engine piston damage if the fuel mixture is adjuted too lean.

Last thing to check is to see if the carburetor throttle plates are in sync. There is a tie bar that opens all the throttle plates in sync. There is a throttle plate adjustment or each carb. Again, the manual will explain how. You can take the plastic cover off of each carb (heald on by three screws) and do a visual check of the throttle plates are all opening together. Doesn't take much to be out of sync.