1988 Force 85HP fuel delivery issue

[jgmart]

I have a 1988 Bayliner with a 85 Force(856x8b) I am having trouble with getting fuel from inboard tank. I only get about 1/2 before engine starts to sputter. When I switch to 6 gal spare tank engine will fire right up. I was told by a mechanic that I should add a 12V low pressure fuel pump after the fuel separating filter. He recommended a 1 to 2 psi pump. I have replaced the fuel lines and fittings as well as the filter element. Any thoughts on the subject? This site has been a Godsend the last 10 years of keeping this boat in the water and running and I recommend it to anyone with a boat.

 

[Frank Acampora]

Bad idea. The 12 volt pumps do not have any way of shutting off if the engine stalls and can pose a safety hazard.

If you can only empty the built-in tank about halfway, you may have a hole in the in-tank pick-up tube or it may even be broken.

 

[pnwboat]

Be aware that if you have a Capri type hull, the fuel tank is only about 8 or 9 inches high. The tank is very long and about 20 inches wide. The fuel pick-up tube and fuel gauge sending unit is usually at the very back of the tank. While under way with the bow of the boat slightly elevated, all of the fuel goes to the back of the tank, thus giving you the impression that there is more fuel in the tank than there actually is. To get an accurate reading, you have to stop and make sure the hull is sitting level. Usually you have to have a couple of people in the bow to get it level in the water. Most of the older Bayliner hulls of this type will read about half full while under way when they are actually pretty close to empty.

 

[Frank Acampora]

So, the first question becomes: How long do you run the engine before the problem arises and how many gallon capacity is the tank? At full throttle you can expect to use about 9 gallons per hour. So, for example, If you are running the boat for 2 hours and the tank is only 18 gallons you are simply using all the fuel.

 

[jerryjerry05]

I think he meant half throttle???
The tank could have: the vent hose blocked off, the pickup tube clogged, crud in the tank.
Or the hose could be bad from Ethanol.
Ethanol rots the hose and it can collapse, shutting off the fuel.

The Bayliners all had the fuel pickup in the rear of the tank

The fuel pump could be weak and not drawing from the tank.
Using a remote with shorter hoses can make a difference.

DON'T install an electric pump, you don't need one.


​

 

[jgmart]

To clarify it only uses about 1/2 the tank. According to original owners manual the tank is 21 gal. I was only able to add 9 gallons at fuel dock with boat level in water. The fuel pump diaphragm has just been replaced due to splitting caused by a backfire when I left fuel line connected and boat was tilted back on trailer with a full tank in the sun, which I assume caused fuel pressure to overfill carbs. With boat tilted back the tank could not vent normally. Lesson learned after losing a long weekend at the lake. I have tried to remove fitting on top of tank to check fuel pickup hose but was unsuccessful. I was able to check most of hose and screen by removing tank sending unit float, which is close to fitting. This area above tank is not an easy access area.

 

[pnwboat]

If you're not sure of the age of the fuel lines, you might want to start by replacing all of them. From the tank all the way to the carbs. The ethanol blended fuels nowadays can cause the inside of the fuel line to break down. Add a see through inline fuel filter between the fuel pump and carbs. Monitoring the fuel in the fuel filter while underway is a good method for checking fuel delivery issues.