Need Help Selecting a Prop

[Tie rod]

Sorry for the repost. Will not let me respell New to Need in my title.


Hi All- I have a 2001 Chaparral 216 SSI with a Merc 5.7 EFI (260 HP) and a Alpha One outdrive with a 1.47 gear ratio. My current prop is a 3 Blade Black Max 1916 19 Pitch. I usually run between 43-49 MPH depending on how many people are in the boat and how much gas. When I am running WOT I hit the rev limiter. I believe it's around 5,000 RPM. My engine should be running between 4400 and 4800 RPM. My question is what prop / pitch should I use. I am just looking for over all performance with the WOT RPM's in the correct running range. Should I try a 4 Blade Prop? Should I use a Stainless Steel Prop? I like the idea of the stainless steel durability.

Currently my boat is in storage at the marina. We are not planning on putting the boat in for another few week. I would like to install a new prop before they put in into the lake. I do not own a trailer so I can't just keep trying props.

Thanks for your help.

 

[steelespike]

Re: Need Help Selecting a Prop

Prop changes aren't cut and dried but a 21" black max should reduce rpm 300 to 400 rpm.
It also may slow hole shot slightly while fading a little quicker as you add people.getting up on skis may be slower.
If the motor can turn it up fast enough top speed could be a little higher.
If you just want to try to take the edge off the rpm a prop shop may be able to add a touch of pitch or a little cup.
But you may have to be more accurate with info about the rev limiter rpm.

 

[etracer68]

Re: Need Help Selecting a Prop

Theres no reason why the prop can't be changed, while the boat is in the water. While your at a beach, or an area where you can stand, and change it out. I would carry spear thrust washer, and nut though. I have changed out a prop in 230 feet of water, on a IO, without to much of an issue.

 

[bnicov]

Re: Need Help Selecting a Prop

Since you are over revving the engine, you definitely need more pitch. A 21p prop should drop you down to the top end of your recommended rpm range and should give you a bit more top end speed by couple of mph. You may notice that it doesn't want to plane out as fast when loaded up. Depending on where you do your boating (ie. lots of rocks) you may want to stick to aluminim since the prop will get chewed up before the lower unit does, stainless is not as forgiving. If you boat in a soft bottom lake, by all means, go with stainless. You may want to think about a 4 blade prop as well. Talk to the guys at the marina to see what they recommend for you.

 

[Tie rod]

Re: Need Help Selecting a Prop

Thanks for all the replies. I decided to go with an Alpha 4 20 Pitch 4 Blade Prop. I read on here somewhere a person with the same Year / Boat Model / Engine / Outdrive combo was using this prop and seemed to like it. I believe the combo of 1 pitch steeper and 4 blades should bring my RPM's down around 300 RPMS. Let me know what you think.

Thanks