View Full Version : where is my speed?

08-26-2007, 11:43 PM
I have an 89 Maristar 240 with a 454. When I bought the boat it was overwheeled, so I sent the prop to S&S in Ft. Lauderdale and they cut it down from 13x15 to a 13x12 cupped. The boat wouldn't even turn the 13x15 (cupped) over 3000 rpm without fouling the plugs. After getting the wheel reworked it still only turns 4200 max rpm with a gps speed of 42 mph with a light load. While the prop was at the shop, I took off the original carb and replaced it with a new 4160. Realigned the motor since it was way off when I bought it. The cutlass bearing is worn, but not terrible. Now, I am still getting fouled plugs after maybe 15 hours of use. I replaced the coil, plugs, fuel filter, and advanced the timing as far as possible without getting detonation. Today, I put one size smaller jets on the primary side (76 to 75) and got a little better acceleration, but still no more speed. Is there something I am missing? Any help will be greatly appreciated.

88 PS190
08-26-2007, 11:56 PM
I know my boat only pulls to about 42 with a 13X13 OJ and a 351.

Not sure what the potential of the 454 in the bigger boat.

08-27-2007, 05:58 PM
what rpm is that at? my concern is that I am now underwheeled and my rpms are still quite low at WOT.

03 35th Anniversary
08-28-2007, 05:17 AM
If you need speed this is the best way to get it. It will turn 5,000+ rpms with most any prop.


08-29-2007, 12:28 AM
yeah, now thats badass. unfortunately my pocketbook just went into cardiac arrest lol, but thanks for the dreaming material.

08-29-2007, 04:36 PM
One other thing, I replaced the hard fuel lines with one that has a fuel pressure gauge. The gauge reads 8 psi. I'm not sure if it is accurate or not. If so, how do I adjust the pressure down? Or, is this even possible?

08-30-2007, 11:10 AM
I think that your 454 should have turned the original 13 x 15 prop to over 4200 rpm. I have a 454 in my Stars and Stripes with an OJ 15 x 20 CUP prop (that I just learned about here last week) and I don't have any problems getting 5,000 to 5,200 rpms. Are you sure that your throttle linkage/cable is opening the carb all of the way? It seems to me that your 454 should have plenty of grunt to spin the prop that you now have. Rick

08-31-2007, 04:46 PM
Yeah, it definitely opens all the way. My boat has a 1:1 gear. I am shocked that you can spin that big of a wheel. Mine just did not want to run with that 13x15. I'm going to look everything over again tomorrow. I found a fuel pressure regulator at auto zone today. I'm going to see if maybe I can get it on there.