15.5x14?????

[jason9080]

i have a 27 foot boat with a omc 460. right now i have a 14.5x19 prop and i get about 40mph at 4200rpms. the guy who sold me the boat gave me an extra prop that says 15.5x14. what would that do on my boat. I would like a couple more mph and crusing speed. also save some gas money. i have no prop getting on a plane right now..
ps the guy i bought the boat from told me i would get 53mph and i have yet to see it. prop??

 

[jason9080]

Re: 15.5x14?????

i meant no problem getting on a plane.

 

[Silvertip]

Re: 15.5x14?????

Since we have no idea what boat you have other than its 23 feet long we can't tell you what its maximum speed might be. If its a cruiser it will never see 53 MPH. If its an efficient planing hull, the engine is in good tune and it is propped correctly, it might. You are also asking for the impossible when you want faster speed and better economy. They don't go together. It takes power to make speed. It takes fuel to make power. Both props have 14 inches of pitch which doesn't sound right for an engine and boat that size. I run a 13-1/4 x 19 on a 75 HP outboard. My 351 Ford powered 19 ft Century ran 17, 19, and 21 pitch props respectively and it would run at 50. Something is amiss here. Verify the tach accuracy and prop size. Things don't compute.

 

[walleyehed]

Re: 15.5x14?????

Computes just fine...gear ratios are different.
This is what happens when we compare 2 different boats with no regard to Final drive ratio, hull style and/or weight.
The 19 sounds close... the 14 pitch would drop your speed and raise RPM considerably...
The OMC drive doesn't require 15-1/2" props, and the design of the blades are more important than diameter anyway.
And, the faster the speed, as long as you are within RPM specs, in most cases, the fuel milage will be better.