240 Sport Prop Issue!
 

HELLO, NEW TO THE FORUM . LAST YEAR I PURCHASE MY 1988 240 SPORT WITH THE 330 MERCRUISER. IT HAS A 19 DEGREE PITCH PROP ON IT THAT I THINK IS TOO SMALL A PITCH FOR THE BOAT. RIGHT NOW IT TURNS 5000 RPM BUT ONLY AT ABOUT 54 -55 MPH. IT WILL SHUT OFF IF I RUN IT OVER 4000 RPM FOR MORE THEN 2 MINUTES. SEEMS LIKE IT RUNS OUT OF FUEL ,I CAN SAVE IT IF I BACK THE THROTTLE OFF BUT THEN CAN NOT SPIN OVER 3000 RPM UNLESS I LET IT IDLE FOR A WHILE. I 'M STARTING TO WONDER IF THE SMALL PROP IS CAUSING THIS ? JUST WANTED TO SEE WHAT PROP SIZE YOU GUYS RUN ON SIMIULAR SET UPS OR IF YOU HAVE ANY IDEAS ON THE SHUT OFF PROBLEM. ITS BEEN A HEADACHE FOR ALL OF LAST SEASON !! THANKS IN ADVANCE FOR THE HELP AND GREAT BOARD!!

It sounds like you might have an obstruction in your fuel line somewhere. As for the prop I think something like a 23 Mirage should be pretty close. I ran a stock 330 hp fuel system on a hopped up 330 5500 rpm with no starvation problems. Your fuel pump may just be tired. Time to get out the pressure gauge and check it out.

Wette Vette thanks for the info. I just replaced the fuel pump with a holley red pump thought that would fix it but it did not .
I also rebulit the heads replaced the exhaust with stainless marine, new performer rpm manifold and completely replaced everything in the ignition from the coil to the module and pick up coil , rebulit the stock q-jet all to no avail. Now I'm going to replace all the fuel lines and get a high flow filter/water seperator . Any other ideas feel free to let me know as this problem is never ending. Thanks

Hey Newcomer, I have the same boat with a rebuilt 454 with a msd set up, check to see if you have a rev-limiter, I found mine in my dash. It may have a lower rpm chip in it. My boat right now runs with a 23-Mirage and does well. Hope this helps!!!

I had a 89 240 sport and a 21p mirage plus was perfect although somewhat slow out of the hole. It kept wot at about 4900 rpm, speed high 50's, 60 on the speedo.

We have an '88 240 Sport with a 454 Mag spinning a 23p Mirage.

The 23p Mirage prop seems like a standard for this boat.



Maureen

Thanks for the info everyone. I'm going to try and borrow a friends 23 mirage and see what happends.

Still sounds like a fuel starvation problem to me. Check the anti-siphon valve in the fuel outlet in the tank, or better still take it out. Hope this helps

syringa

Anti-siphon valve!! Anti-siphon valve!!! I have the same boat as you J240, and had the exact same issue several years ago. Removed the anti-siphon valve (top of the tank, where the fuel line goes out to the motor off the top of the pickup) and the issue never came back. I put a simple nipple fitting on the tank. Problem solved.

21 Mirage will be your prop of choice. The 23 will not spin fast enough, you might get 4400 rpm out of it, making the motor work very hard at WOT. Your motor should run 4600-4800 at WOT. More than that and you are asking for trouble from your stock 330 internals. Mine would do 56 with the 21 when I was running the 330 in it. About to install my re-built, 450 hp motor. Can't wait!!!!

Mike

Anti-Siphon Valve hug?? I have removed the pick up coming out of the tank that feeds the motor and it was a tube about 8 inches to a foot long with a 90 degree elbow for the fuel line at the top. On the bottom was mesh screen material that I cleaned several times hoping it was clogged but it wasn't. Where is this valve and what does it look like ,could mine be somewhere else in the line running to the motor ? Thanks for the help.