Engine losing RMPs problem

[ozzy]

Went out to Gulf Monday in a 28' CC 1998 gas engines. Running about 3200 rpms everything was running great. At about 20 miles into a 60 mile trip the port engine rpms starts to die down. Pulled back and tried to get on plane again. After throttling up the engine died down to about 1500 rpm again. Stopped the boat and put on a new fuel filter. Ran out to spot, fished for about 6 hrs then throttled up to come back in. The engine did the same exact thing. Could not get teh filter off this time as the strap wrench broke and the filter was too tiight. Rode a few miles as at about 12 knots and decided to try throttling up again. Managed to get the engine to about 2800 and had the other around 3000 in a rough sea. Averaged about 19 knots and made it back and burned approx 25% more gas than I should have.


I was running off the saddle tanks going out and figured that the port tank may had had water or debris in it so when we changed the filter I switched to the main and it did it again on the way in after both engines ran fine the entire day out and fishing.

Any suggestions as to what this could be? Could that much gas be wasted?


Thanks

[Nutz]

Something similar happened on an old boat, not a CC. I wasn't getting the gas I needed and the filters were new, boat would bog down. The problem was the pickup tubes on the tank were getting clogged with debris. There was a strainer on the tube to pick up larger debris and it was clogged up. Mechanic told me to check the anti-siphon valve on the pick up tube too. I dont know the set of the tanks on the CC boats but something to think about.
On my old tank the tubes would screw out. The antisiphon valve was where the tube connected to the hose, essentially a ball and spring.

[Armageddon]

Yes, there is a 99.9% probability that this is a fuel restriction problem. I am not familiar with CC's with gas engines (I have diesels), but the same should apply if your engines are bogging down and starving for fuel. Replacing the fuel filters is not the answer. First, you have to take out all of your fuel tank intakes. If there is a screen on the intakes, REMOVE THEM PERMANENTLY. This was recommended by my Volvo Mechanic. You want to get the debris trapped in your tank out of your tank, and the screen not only prevents this but it cloggs your intakes. Let your primary fuel filter take care of the debris by getting it out of your tank and into your filter. That is what a filter is for.

While you have the intakes removed, you have to check your anit-siphon valves to make sure nothing is trapped inside and causing the "ball" in the valve from springing back and forth. The valve is a brass fitting that screws into the intake. Our tanks are made of aluminum and when the manuacturer of the tank was soldering these tanks, most tanks will have metal shavings, solder pieces, etc. trapped in the tank. The only reasonable way to get these out is to remove the screen and clean out your intakes periodically by removing them.

When you are offshore in any kind of seas, the moving will draw these shavings and solder pieces to the intakes. After you remove the screens you will notice these pieces in your primary fuel filters.

A good way to "clear out" your fuel line to remove stuff that may be stuck in your filter pump is to remove your fuel filter and place a small bucket under the filter pump. Pump the filter and watch the fuel with "junk" come out of the filter pump and into your bucket. After you feel comfortable that your removed most of the debris, put a new fuel filter on and follow your installation procedures. DO NOT OVER TIGHTEN ANY FUEL FILTER. Fuel filters are to be hand tighened and tightened 1/4 turn more and not more than that. Your rubber gasket on the filter insert will prevent any leaks.

Please note that the "clear out" procedures above are to be used for your Primary filter only. Do not follow this procedure with your secondary filter (the filter on the engine itself.) Follow the manufacturer's instructions for the secondary fuel filter.

Let me know if this helps.......

[ozzy]

Thanks guys all this info is great.

I did have some time today and took off the fuel filter on the engine that gave me problems and it had sediment in it, kinda rust colored. I have not had a chance to run it though other than to fuel up.

Armageddon, when you say the fuel intakes what exactly are you referring to? The fitting on top of the main tank inside the inspection port near the live well? I have 3 brass fittings with hoses connected to them. If so is it ok to do this with gas in the tank?

Thanks again

[Nutz]

I had some gas in my tanks when I did mine. That fitting should connect to a long metal tube that goes to the bottom of your tank. The screen in the tube may not be visible. Run a coat hanger or something similar thru it after you remove it.

[ozzy]

when you remove the fitting how do you prevent gas from spewing all over?

[Armageddon]

The intakes are screwed into the tank from the top. You should have one intake for each engine, looks like a 90 degree fitting, an anti-siphon valve screwed into the 90 degree fitting and finally a fuel hose attached to the anti sipon valve. If you have 3 fuel lines going into your fuel tank, then the third may be for your generator (if you have one.) The intake has a pick-up tube, which is a tube that extends to the bottom of the tank, just like Nutz describes. Your anti-siphon valve is used to stop fuel flow from returning back into your tank for safety reasons, especially on gas engines. Usually you have to pull off the fuel line from the anti-siphon valve first to unscrew the intake. It is easiest if you cut the fuel line slightly at the end where the anti-siphon valve is to help the hose to release from the barbs on the anti-siphon valve. You want to have several rags and maybe a small bucket or cup handy for spills. When you remove the anti-siphon valve from the fuel line to inspect and clean, a rag will usually do the job. Remember, your engine has been starving for fuel. You should not have too much fuel in the line to spill all over the place. I didn't say this wasn't a little messy, though ....

I would not recommend taking off any more fuel filters until you clear out your intakes. It does not sound like your filters are the problem at all. You're not getting enough fuel from your fuel tank to go through the filters to begin with.......