engine rpm fluctuating

[jleblanc30]

Hi,

In doing maintenance this year I changed and cleaned both fuel filters. Since then I have reoccurring issue. After about an hour of running the engine the rpm start fluctuating up and down with the engine eventually dying.

It always restarts and will do it again for 15 to 20minutes. After giving it a break of about 20 minutes it restarts and works fine.

This has happened three time in the past three weeks.

I'm thinking my fuel pump may start to give or I have air leaking in the system.

Any thoughts?

Thanks

Jean

 

[Stu Jackson]

Year of boat? Engine? Always helpful info for us to help you.

Let's say you have an M25-series engine:

potential culprits:

- just because you changed the fuel filters, doesn't mean you shouldn't check the primary again

- where is your fuel pump? If before the primary filter, move it to behind it, then check the built in screen in the bottom

- fuel pickup hose in the tank; is the engine/boat old enough to still have the screen in the pickup tube? Blow back through from the filter to the tank or check phsyically

- leaks, always a possibility

See this for the full story:

Critical Upgrades http://c34.org/bbs/index.php/topic,5078.0.html

 

[jleblanc30]

The boat is a 1987 with a M25. I bought it last year and had no issues with engine, which I was told had an oil change. Reading more about the engine maintenance I realized I did change the fuel filter, so I did. I didn't clean the fuel pump filter as I didn't know there was one.

I will check the pickup hose and clean the fuel pump filter.

Thanks for the info.

 

[Coriolisbc]

My engine rpm was doing the same thing on a 9 hour motoring trip back to home port, luckily a week later we started the M25 at the dock and it died, for me it was the fuel pump, now replaced, just glad it did not fully die on the trip home earlier. 1988 C30

 

[Stu Jackson]

You can get less expensive replacement fuel pumps at an auto store.

 

[barnstormer]

The boat is a 1987 with a M25. I bought it last year and had no issues with engine, which I was told had an oil change. Reading more about the engine maintenance I realized I did change the fuel filter, so I did. I didn't clean the fuel pump filter as I didn't know there was one.

I will check the pickup hose and clean the fuel pump filter.

Thanks for the info.

Definitely check the fuel pump screened filter at the bottom of the fuel pump. There is a nut at the bottom of the pump when turned causes the cap to drop down with the screened filter to be accessible. Many people don't change this filter cause they don't know it's there. I have an '87 m25 and the screen was starting to collapse on itself due to all the crap that was built up on it.Motor ran higher and lower r.p.m. after changing and made a big difference.

 

[Stu Jackson]

barnstormer, that filter will never plug again if you replumb the hoses to it and relocate the pump to after the primary, as suggested in the link I provided.

 

[jleblanc30]

Thanks everyone for your answers. I will change the filter in a couple weeks and let you know the outcome.

Best regards,

Jean

 

[jleblanc30]

No luck

Well I changed the pump filter, but the problem came. Next I will check the fuel tank. I have ordered the fuel pump $250, outch...hopefuly it is the tank and I can return the pump.