Whats a good prop upgrade for my 4.3 litre mericruiser

[xcelr8z28]

I am looking for upgrade my properller on my 18 foot ebbtide ski boat, im not too experienced in boating, i have an aluminum prop on there now, and she goes about 30 mph. I would think a 4.3 litre mericruiser, and alpha 1 sterndrive would get me up near 40 or 50 mph, what should I do???

 

[WillyBWright]

Re: Whats a good prop upgrade for my 4.3 litre mericruiser

Not over 50. Mirage stainless props are nice, so are Alpha 4-blade aluminums. The Mirage will be faster. The main thing is to get a prop specifically designed for sterndrives. The 3-blade alulminum props most come with are multi purpose and do a generic job of pushing the boat.

 

[tmh]

Re: Whats a good prop upgrade for my 4.3 litre mericruiser

It's not primarily the type of prop you have a problem with, that may make a 3-5 mph difference once you know what pitch you need. Right now, you are WAY OFF performance wise and need to find out why. You are correct that you ought to be well into the 40's at least. This isn't a prop "tweaking" issue, it's a "find out what's wrong" issue.

Is the current prop just completely mis-sized for your boat or is there an engine issue? Answer that before buying new props.

What is your max rpm at WOT? What pitch is the current prop?

 

[xcelr8z28]

Re: Whats a good prop upgrade for my 4.3 litre mericruiser

the engine runs fine. im not sure the wot seeing i've only used it once, but i will fine out this weekend and reply. the engine gets serviced twice a year so I don't know what possibly could be wrong with the motor.... but i will investagate thanks for the help

 

[coooeee]

Re: Whats a good prop upgrade for my 4.3 litre mericruiser

I'm a novice my self but by way of comparison my 4.3L Alpha 1 (220hp) gets me to 50mph in a light 20' boat at 4800rpm. That's with the 21" Black Max.

coooeee!

 

[xcelr8z28]

Re: Whats a good prop upgrade for my 4.3 litre mericruiser

I check out the prop on my boat now its a Michigan Wheel Vortec, 14" and has a 23" Pitch... Also im not too sure if this would affect the top end speed, but i have a minn kota trolling motor attached to the top of the main outdrive.. would this be a problem??

 

[tmh]

Re: Whats a good prop upgrade for my 4.3 litre mericruiser

You need to verify WOT (Wide Open Throttle) RPM and MPH. That will show where you need to go with your prop.

IF it's only 30 mph, I assume your rpm is too low also or you'd be flying with a 23" Pitch prop. First guess is you certainly need a lower pitched prop, but I still think something is off. The 23" prop would give you a lousy hole shot but should be able to get decent top speed even if it's not allowing you into the proper top end RPM range for your engine. A boat that should hit the high 40's doesn't only get 30 mph unless there is a pretty significant issue. It MAY be the prop, or the numbers aren't accurate. I'd say less likely the prop if that is all she has in her.

So, just test it, check the max RPM and MPH and report back. You'll get guided in the right direction once folks here have that important info.

Also, what HP is the engine and how old?

 

[xcelr8z28]

Re: Whats a good prop upgrade for my 4.3 litre mericruiser

The engine is a 1993, 190 HP. Its been to the shop twice a year, always serviced and well maintained. It sounds brand new while running/Idol. I will check the WOT, and MAX speed Friday when i take her out for the weekend. The highest that I got it was around 32-33 MPH. Thanks for the help