rpm fluctuation...

[hotmerc]

1988 carver santego 27, twin 98' 4.3 ltr vortec with 4 blr. weber carb...
been having an issue with port motor. when planed off at @3500 rpm i get a drop then a raise in rpm, up and down, never steady like starboard motor. im thinking its some sort of fuel issue. changed fuel filters and rebuilt carb, looked like floats were out of whack, readjusted to specs in maintenance book but still have the same problem. any ideas?

 

[dubs283]

Re: rpm fluctuation...

when was last complete tune-up done?? plugs, wires, cap, rotor, ignition sensor (new style, complete black potted plastic), fuel filters, set timing, adjust idle, test drive

 

[JustJason]

Re: rpm fluctuation...

test the boats fuel system yet?

 

[hotmerc]

Re: rpm fluctuation...

new plugs end of last season, checked and cleaned, new ignition wires, filters, cap & rotor, was timed out last season, fresh fuel as of 2 weeks ago. starboard motor runs off the same fuel, no issue there...

 

[myfirstboat1984]

Re: rpm fluctuation...

I was having the same type symptoms and you. I rebuilt my carb first. it needed it badly anyway, so no harm done. It didn't fix the problem. Then, I tested my fuel pressure, and it was bad low. Luckily my fuel pump had a rebuild kit. I rebuilt it and that fixed the problem.

I got the fuel pressure kit from Auto Zone. They let you "borrow" it for free.

 

[hotmerc]

Re: rpm fluctuation...

do u have an electric fuel pump?

 

[Bondo]

Re: rpm fluctuation...

fresh fuel as of 2 weeks ago. starboard motor runs off the same fuel, no issue there...

Ayuh,... But that Ain't Checking the other motors Fuel System,... Tank to Carb....

 

[myfirstboat1984]

Re: rpm fluctuation...

the rebuild I did was on an 1984 mercruiser mechanical pump. Most people I've read about on this forum aren't so lucky to be able to rebuild a bad pump. Like the admiral said, a complete check from the carb to the tank is in order. You may not have to replace an expensive part like the pump.

Good luck.