I know that if you use undersized pulleys in an automotive application there is improved hp. Does this work with a marine application? Will this cause any other problems? TIA, 88 Mach 1

I tried a undersize crank pulley and my oil temps skyrocketed.

Jon

We're running twin Merc 575SC's. Based on our mechanic's recommendation, we dropped down to smaller supercharger pulleys which increased our HP to 650's. We gained more torque and a few MPH on the top end. We're still tinkering with props, but overall the engines run great!!

well no superchargers here, just looking to get a few more cheap HP with a pulley change

You're not going to feel a difference on a N/A engine by changing your pulleys.

I agree with Rumrunner. Unless you are running a 1000 lb boat you will never notice any gain. And you are running an 88 Mach 1 (at least I assume from your name). Definitely NOT a 1000 lb boat!! There have been several posts lately about removing this or that to get that "extra free hp" and it's just not worth the effort. Power steering?? No. Water pump? No. The only way to get more hp is to build for it. Head work, carb work, exhaust, raising compression, etc... are the best ways to get hp gains. Or adding a blower as some have done.

Underdrive pulleys in a car only give about 5-10 hp additional power. That might equal .1 second in a 1/4 mile in a car and 5-10 hp will equal nothin in a boat.

Thanks for all the input. I guess just and exhaust upgrade and maybe ingition to add to the fresh 500 hp 454. Thanks again, 88 Mach 1

I run the Imco hi rev dampener pulley and the hi rev water pump pulley. It slows all of the accessories mainly for boats that see a lot of rpm on a regular basis. I didn't see a speed increase. I did notice the steering is stiffer at cruise and the water pressure came down slightly. My motor sees 6200 RPM on a regular basis. Spend the money on props or something that will move the needle especially if running lower RPMs.