Another prop ???

dstockwell · Post by **dstockwell** » June 17th, 2005, 9:33 am

This is the prop originally on my Merc 200, a bulky 141/2 X 17 looks like it belongs on a Mercruiser or similar. Best this thing will do is 36 - 37 @ 5K, any attempt to trim causes the boat to porpoise. So I decided to raise the motor one hole in an attempt to trim it out, forget it same thing happened.

I went back to the dealer to try a 14 X 19 Merc Vengeance (size based on Merc prop calculator). Response much better speed @ 5K 40 MPH, range of trim far more than I ever had. Now when I trim the motor to achieve 5400, speed will drop off to 36, is it because I raised the motor one hole.

Post by **Tom Keels** » June 17th, 2005, 9:38 am

You need to go down in pitch to increase your rpms. Props with too much pitch blowout and lose bite when you trim it out. I would go down to a 15 pitch SS and maybe a four blade for running in the gulf.

pennfish · Post by **pennfish** » June 17th, 2005, 11:19 am

Is that boat/engine combo a normal set up for the boat MFG.

dstockwell · Post by **dstockwell** » June 17th, 2005, 11:22 am

pennfish wrote:Is that boat/engine combo a normal set up for the boat MFG.

Yes. I had moved the motor up one hole because of the problems with the previous prop, so I think I will move it back down one hole and see what happens.

pennfish · Post by **pennfish** » June 17th, 2005, 1:11 pm

See if you can locate other owners of the same rig and ask if they are having any performance problems. Is that a Key Largo? how much does it weigh

dstockwell · Post by **dstockwell** » June 17th, 2005, 1:30 pm

Key Largo yes, weight 2400 dry, so with motor, fuel, gear, 2 people its about 3800 lbs.

Post by **tin can** » June 18th, 2005, 5:48 am

Doin. is 5000rpm at WOT? If so, 19 is too much pitch. That's a lot of pitch for that size boat. Mercurys like to turn high rpm. You stand a better chance of damaging the motor by loading it, not turning enough rpm, than you would over turning it. Back off to a 17.

As for the blowout, an offshore boat's bottom is mot conducive to over trimming. You should be able to trim up 2/3 of the trim range, turn 5500 rpm, and not drop any speed. Lowering the motor back down might help some, but I doubt it.

Bottomtime · Post by **Bottomtime** » June 20th, 2005, 9:31 am

Don, I have a 14.25 X 17P Stiletto prop that only has about two hours of use on it. It uses the torque flow hub system, but I don't have that in it. You are welcome to give it a try and see if it gives you any better performance. It came with my 250 HPDI, but didn't have enough surface area to push my 24' Cape Horn very well. Let me know if you're interested in trying it out.