Trojan Boat Forum

Does anyone have any experience on putting new 4 blade props on an f32? A freind of mine just repropped his Sea Ray and is seeing 15-20% reduction in fuel, with a better out of the hole experience, but I would have no idea where to start on sizing. t250 Chryslers.

Any insight is greatly appreciated

I believe my 4 blades are 14x17.

If your propped right now don't expect a big difference in fuel burn .( 15-20% is a lot) using the specs on the props you have and the engine performance your getting a GOOD prop shop should be able to get the proper size figured out .

If your boat has the same engines and gear as readys then what he has should be real close for sure

ready123 wrote:I believe my 4 blades are 14x17.

Did you notice any differences with the 4 blades you can share? I currently have two sets of three, and the boat seems to perform well but was wondering if it could be better.

About 17k at 3100...

Cmount wrote:

ready123 wrote:I believe my 4 blades are 14x17.

Did you notice any differences with the 4 blades you can share? I currently have two sets of three, and the boat seems to perform well but was wondering if it could be better.
About 17k at 3100...

Low speed control much better.. easier to dock more responsive. Get's on plane easier and seems to hold her up at a lower speed.
Can't comment on fuel burn as no direct measurement so all my calculations are guesstimate
I have always looked at fuel as my boating's lowest expense, so just keep the engines tuned and spend what I spend for gas.
I had 4 blade props as spare so had them tuned and put them on... now my three blades are the spares.
Look back some years (3?) in the archives and you might find more detail than that from me.... I'm into diesels now

Thanks so much...these are the exact things he said about it on his boat's performance. I am going to start to look for a pair and see what the costs are. I am like you much more into the handling of the boat, not so much about the gas. I just feel like it can be better and like what you have to say. I will dig back tonight.

Thanks Again,
Clyde

So I finally got to test. 4000rpm's 25.5 knots 3000 18.5 knots...318's

Great around the dock, faster ilde and low RPM speed...but I am thinking I need either another 1/2 in to inch of pitch or a more pronounced cup for slippage. I was hoping for 20knots at 3000 rpms.

Can anyone share with me what thier three blades do at WOT and 3000 rpms? I would appreciate it. http://s814.photobucket.com/user/CJMOUN ... t=6&page=1

What did you take off? I am turning 15x16 3 blades w/ the Merc 228's and 1.52:1 BW's. If your speed numbers are accurate, you are gonna have to do something if you want to race.

All kidding aside. I think you are running too small a diameter wheel. If I changed wheels, I would look to go up in diameter and down in pitch as compared to stock on an F-32. Honestly though. Unless you repower. What it came with is proper for the application.

Unless you have access to a large variety of props which you can borrow to test, its going to be expensive to buy enough used sets to properly determine the best prop for the boat. Think just under a grand with shipping per set for decent used wheels. Think 4 or 5 sets to properly test different options. Everything else is just a shot in the dark. Overpropped and it will lug all the time, underpropped and it will rev through the roof.

FWIW I have a 4 blade jobbie on the Nautique. Its what it came to me with. Its a ski/pulling prop. Great hole shots, but a lot of that is due to a Ford 351 with a 1:1 drive in a 2300 pound boat. WOT at 4000 gives me close to 50 mph in that boat. It has the torque to change props to a "cruising" variety, which would decrease my hole shot ability, but increase my top speed. The "cruising" variety of props for that boat are all 3 blade props, and the ski props are 4 bladers. Some more food for thought.....

Took off 16X16's...looks like I picked up 1.5 to 2 knots at 3000....plus better out of the hole for sure, on plane at a little lower RPM's. Just expected a little more. We may try to cup them a little more. I am talking with the prop guy now, as that was all included in my price, so I may ask him to try a cup for slippage.

Deffinately improved aound the dock...so in all it was an improvement... was just hoping for a little more.

And really looking to benchmark against others...it seems to be about what others in good shape do at the moment. 250hp now so a little lighter than the Crusadres.

What was your original power plant and what gear reduction do you have? Its kinda hard for me to comment much without knowing that info first. Also what power plants do you run now, and are you using the same gears?

You took off 16x16 3 blades and went to ?x? 4 blades? Same or different? My first try after taking off 16x16 3 blades and going to a 4 blade option would be a 15x17 with a slight cup. Less diameter to make up for the increased mass of 4 blades, and more pitch to compensate for the decrease in diameter. Opposite of what I would do if repropping an F-32 with a different set of 3 bladers.

So one plant is the original 318 250, and the other is newer 275 318....1977 and 1987 respectively.

Went to 4 blades...14*17....and I actually asked about increasing to 15*17 just this am..(may try a larger cup first)..as I get full top end and expected it to be a stuggle to get there and it was not at all hard to get it...so interesting that is your gut.

The gears I will have to check but should be the orginal velvet drives. I will pull them over the weekend.

If 15x17 was too much on that first try, my next try would be a 14x17 with a decent cup. I think you are close, but would try 15x17 before i cupped out the 14's. You can always do that later if the 15's are too much.