Prop setup.

**RSWORDS** · 08-22-2018, 04:48 PM

Not getting very much traction in my other thread about the boat so I thought I'd ask here. My 25 foot long 9 and 1/2 foot wide c-hawk with a 250 EFI is spinning a 17-pitch inertia to 5800 RPM at around 43.5 to 44 mph and 18% slip (calculated). At this point I believe the soft limiter is what's holding me back, I'm wondering if I'm going to buy a couple props to play with, what should I be looking at?

While topspeed is a concern, its notnTHE concern. this is a family style boat that I will pull tubers with. Right now even with the inertia and the motor set with the anti-cavitation plate about an inch above the bottom of the boat it'll cavitate if I go into a moderate to hard turn. Even with the motor tucked all the way in.

I'm wondering if I should try a 19 rev4, a 19 Mirage Plus, or 19 inertia. I'm open to any suggestions.

This is the boat, running at about 4800 RPM.

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**RSWORDS** · 08-23-2018, 10:25 AM

All right, just went out and ran a 19 pitch inertia. RPMs are at 5500, speed came up mile and a half or so. Slip went to 22% though.

**David** · 08-23-2018, 11:36 AM

Have you tried the prop selector on Mercury's web site? A four blade might help with the cavitation.

**RSWORDS** · 08-23-2018, 06:29 PM

Originally Posted by David

Have you tried the prop selector on Mercury's web site? A four blade might help with the cavitation.

I have. We use it alot here at work. AMD for a "normal" boat I would be happy with the 19 on it now. But I know there is more

**R.I.P.** · 10-01-2018, 11:53 PM

Each pitch is around 300 rpm.
On a boat that is not performance based ,you have a hull design that will slow you down. It's not prop slip its hull efficacy. Look up your motors wot rpm. You can add a few hundred, but dont go crazy

**KIRCHNER** · 10-05-2018, 09:33 AM

Looking at your rig, i think u need to lower your motor,to reduce the slip & cavitation. find a used 4 blade and give it a try. my 2cts.

**phillnjack** · 10-07-2018, 10:38 AM

Does this boat have a keel ? if so lower it so the cav plate is 1 inch under the transom.. before buying all new props I would experiment with heights. the slip figures are pretty high that your getting, are you sure of the gear ratio your putting in ?
is this definitely a 1.75 to 1 or could it be a 1.87 to 1 ? this later ratio would drop your slip to around 11.75% and that would be more acceptable .
from the manual it states this was an optional high altitude ratio ?????