4 blade prop

[Jeff Pyper]

I am new to boating. Sundancer 270, bravo3, 383 stroker IO. Considering changing from 3 blade duo prop to 4 blade for increased economy. Use the boat at slow cruise, or high idle mostly, 2-3000 rpm. What should be my concerns? Thank you

 

[paulswagelock]

A bravo 3 four blade prop set will run $1000. It will take you 20 years to break even on fuel economy.
There could be worthwhile advantages of a 4 blade set, but this is not one of them.

 

[Brite Idea]

You definitely will get better performance. What pitch are you running and what is your WOT?
I have a heavy boat with twin 5.0 Bravo III's. I was running 22 inch three blade and cruising at 3600 rpm but it was a struggle to get on plane. My WOT was 4560 which is too low. I switched to 20 inch four blades by Hill Marine and the boat gets on plane much easier. I lost about two mph but fuel economy went up and now my WOT is 4850 which is much better. Hill Marine was great to work with and he even bought my old props.

 

[Josh28161]

You definitely will get better performance. What pitch are you running and what is your WOT?
I have a heavy boat with twin 5.0 Bravo III's. I was running 22 inch three blade and cruising at 3600 rpm but it was a struggle to get on plane. My WOT was 4560 which is too low. I switched to 20 inch four blades by Hill Marine and the boat gets on plane much easier. I lost about two mph but fuel economy went up and now my WOT is 4850 which is much better. Hill Marine was great to work with and he even bought my old props.

Good info! Where is Hill Marine? I am thinking about changing to 4 blades as well and would appreciate some professional guidance.

 

[dwna1a]

Go online and check out Black Dog or Michigan Wheel

 

[paulswagelock]

Hill marine 4x4 props work well on underpowered boats. I used them on a cruiser I had and it made the boat plane easier and reduced the cruise rpm needed just a bit. If the boat is adequately powered, they typically do not do any better than the standard 4x3 Merc props.

from my post in 2013:

I have a 28' cruiser, about the same weight, with the 350mag. Had 20p 3x3 props. 40 mph, 5100 wot rpm, best efficiency was 3900 rpm and 31 mph. Switched to Ron Hill 22p 4x4 props. 5000 rpm wot, 40 mph top speed, optimum cruise speed is 32 mph at 3600 rpm. Fuel use went from 2.1 mpg to 2.3 mpg at the optimum cruise. Also, all prop cavitation dropped off at higher trim, no blow out on harder turns either. Minimum plane speed went from about 24mph down to 20 ish.

My holeshot was spectacular with the 20p, truly amazing for a single engine cruiser. It is still very strong With the 22s. I can still get on plane with full gear and full passenger load in a reasonable distance.