How much Prop should i try?

[svb165]

I repowered from a 5.0 to a 5.7. 260 hoss to 300hp my dilemma; how much more prop should i try? 2",,3" ,, 4" in Pitch 3 or 4 blade.? do i need to go smaller dia as i increase pitch ect..

its a 2006 20' CC speedster 5.7 mag mpi , alpha l gen ll 1.62 I/O it weighs about 2860 lbs.
stock Prop. for the 5.0 260hp motor is Vengeance SS 13.75" 21P
im thinking of trying out a four blade SS at 24P = 3"
or do i stay with a three blade SS and try going up 4" i feel 2 in increase wont do it but, i cant make up my mind and the more i research it the less i know.....







































.?

 

[Scott06]

I repowered from a 5.0 to a 5.7. 260 hoss to 300hp my dilemma; how much more prop should i try? 2",,3" ,, 4" in Pitch 3 or 4 blade.? do i need to go smaller dia as i increase pitch ect..

its a 2006 20' CC speedster 5.7 mag mpi , alpha l gen ll 1.62 I/O it weighs about 2860 lbs.
stock Prop. for the 5.0 260hp motor is Vengeance SS 13.75" 21P
im thinking of trying out a four blade SS at 24P = 3"
or do i stay with a three blade SS and try going up 4" i feel 2 in increase wont do it but, i cant make up my mind and the more i research it the less i know.....







































.?

I did a similar repower went from a 190 hp 4.3 to a 260 hp 5.0 on a sea ray 200 sport. Kept the 1.81 V6 drive . Boat had a 19” vengance on it. Found going up 2” in pitch was roughly equivalent to one step in drive ratio as with a 5.0 my boat would have come with a 1.62 drive witha 5.0.

what wot rpm did u get with the 21“ pitch? If it was at top of rpm range I would go up 2” and you should be ok. If you add an extra blade would reduce pitch a bit. I played a round witha few props 21” vensura 4 blade, 22” enteria 3 blade, and ended up with a Revolution 4 21”.i do a lot of loaded watersports so holeshot and stern lift are king for me.
vengeance is a pretty basic prop I’d be inclined to try a 23” enertia or revolution 4 based off the limited info provided. you May be best dying to find a prop shop that will let u try before u buy. I think prop gods, bblades, and prop md do some sort of exchange programs via ups.

 

[jimmbo]

First of all, what are the WOT Rpm Ranges for both the Old and the New Engines? What WOT rpm were you getting with the Old Engine?
If the new Engine has a WOT Range that is higher than the old engine, you might not need a pitch change.
Now switching from One Prop Line to Another, often isn't as easy as picking the same Pitch as the old Prop. Blade Area, Blade Shape, Cupping, Rake, type of Pitch(Flat or Progressive) all affect how different Lines of Props perform.
I myself, am a big fan of the Enertia, and have been running one for 19 or 20 yrs, and have only seen one Instance where it didn't perform well.
My Avatar shows my boat running the Enertia. It is an 18 1/2 ft with a 5.7 260hp(2bbl) and just shy of 300hp(with 4bbl). The Enertia is very good at Lifting the entire Hull vertically out of the Water. It is not over trimmed, as the Prop Shaft is parallel to the direction of travel

 

[jlh3rd]

+1 on what are the current running #'s and engine specs @WOT. That's the baseline starting point, not what someone hopes, thinks, or guesses. There is a propping sticky on here.

 

[Pmt133]

Like everyone else said... what was it running and what is it running. Once you have that data go from there. Otherwise it's just a WAG.

 

[svb165]

yes you are right, it is just fishing a bit while its off season.. i did not run the boat with the 5.0 so i dont know the rpms @ wot with that motor,, and i have not yet fully broken in the new engine so i dont know the revs of this one yet. i guess i was hoping to find a similar vessel and powerplant to get an idea where to start. thanks i will have to wait for spring to do the proper testing.

 

[Scott06]

yes you are right, it is just fishing a bit while its off season.. i did not run the boat with the 5.0 so i dont know the rpms @ wot with that motor,, and i have not yet fully broken in the new engine so i dont know the revs of this one yet. i guess i was hoping to find a similar vessel and powerplant to get an idea where to start. thanks i will have to wait for spring to do the proper testing.

This is same situation I ran into with my repower. Boat wasn't running as it was sold as handymans special.

If the boat manufacturer sold that boat with the 5.7 300 hp see what prop they would put on it. Sea Ray published that in their parts book.

I started out with the existing prop (19" Vengence) that was on it with the 4.3 . First time in the water I was doing break in anyways so didn't hammer it just varying speed at mid range rpm. First week end got enough hours to get it near WOT max rpm and of course had a lot of throttle to go at redline. You will probably be in same spot and have to guestimate off how much throttle is left

You can do some math to ball park what pitch would give you the same rpm with the 'wrong' drive ratio. Basically on back of napkin showed that each drive ratio step was roughly equal to 2" pitch. I think my swag said I would need a 21 or 22" pitch. I went with a 21" 4 blade Vensura and it worked fairly well. More for my own edification I spent the next 2 years trying several different props before I settled on the Rev 4. I put searches in ebay and bought them when I found good prices on used ones. I still kept the Vesura as it is a close second Sold the Enertia for close to what I paid for it.

 

[jimmbo]

a 4th blade will certainly load the engine more, and kill top speed by several mph below what a 3 blade would do. Having the WOT range of both engines will certainly be of help, in making guestimates