Props

W

Wooly

Active Member
hey all,

I'm looking at trying out some different props for my boat.

Any advice on what would be best for my application would be greatly appreciated.

I run a 25 ft aluminum probably close to 6000 pounds on the heavy side when fully loaded. Dont really care about a whole shot as I have lots of power. More interested in lowering my RPM while plaining to save on fuel as my trips are long. 250 horse Honda. just in the process of throwing on trim tabs as well. Is it just trial and error? If anyone has some advice on where to start that would be sweet.

Cheers,
 
Holy %^**#% wooly you didn't get tabs from the factory crazy. Also what people say the prop should do might not do it with props it's try it if you don't like it switch but the problem is you can't return them. Lol sooo be careful when you pick
 
I played the same game wooly. After much playing around a four blade kept me up planing 200 rpm less. Dropped 2 inches of pitch and went to a four blade.
 
what prop are you currently running? what are your current numbers rpm at what speed? what speed does the boat plane out nicely?....if your current prop is working and getting you to your max rpm, you can use it as a starting point and fine tune from there...general rule of thumb increase 1degree pitch will lower the engine 200rpm...but if you are looking for economy on a heavier boat I would be lookin towards 4 blade prop...if switching from 3-4blade that rule of thumb goes out the window...more info would help...and yes props are a bit of trial and error but you can make some educated guesses
 
Talk to your dealer before you buy when I got my last prop I was told I could exchange it if I wasn't happy with the results after a quick sea trial. Thankfully i didnt need to. You can Probably put a couple hours on it and exchange it if its not what you want just clarify that before you buy.
 
Yeah was kind of a poor descision on my part. I thought I could get away with it with the pod. but i load up too much so they will help. Really it didnt do too bad without them, I just want to make sure its perfect now.
 
I'm running a 19 pitch 3 blade right now stainless. i had it 5800 rpm goin 46 mph fully loaded. I was planning at a min of 3900 but that was very loaded and poorly packed. My economy 8-10 gph came around 4500(thought was high?) going 27-32 mph doepending on current and wind. I can keep the boat on a plane going about 20 mph i think the rpm was 3900-4000.

when i did the trial with no weight on board i think it was 17 mph on plane with 3400rpm. Very happy with the results as they were right around what i expected but curious if I can do better.
 
GDW said:
Talk to your dealer before you buy when I got my last prop I was told I could exchange it if I wasn't happy with the results after a quick sea trial. Thankfully i didnt need to. You can Probably put a couple hours on it and exchange it if its not what you want just clarify that before you buy.
Click to expand...

i'm good buddies with the marine shop here so i wont have any issues exchanging and so on.
 
I would try sticking around that pitch or the closest available in a 4 blade, (18-19pitch), that will lower your rpm to speed, and more prop surface area alows less "slippage", more efficient especially for a heavy boat...your rpm will drop at WOT, as will your speed, but should be more efficient in the cruise range...i think 4500rpm at 27mph is a little high too...im also assuming this engines max rpm is 5000-6000rpm...the 4 blade may bring you down as low as 5400rpm WOT....again this is just going by the general rules, but thats where I would start
 
ComfortZone said:
I would try sticking around that pitch or the closest available in a 4 blade, (18-19pitch), that will lower your rpm to speed, and more prop surface area alows less "slippage", more efficient especially for a heavy boat...your rpm will drop at WOT, as will your speed, but should be more efficient in the cruise range...i think 4500rpm at 27mph is a little high too...im also assuming this engines max rpm is 5000-6000rpm...the 4 blade may bring you down as low as 5400rpm WOT....again this is just going by the general rules, but thats where I would start
Click to expand...


My understanding is the higher the pitch the lower the RPM? therefore I wouldnt want to go lower then 19? That sounds interesting maybe i will try a 4 blade.

Yes they said optimal rpm is 5300-6300 for WOT.

I dont think my boat is considered heavy though, its actually a very light aluminum when compared to other boats its size and style. However i personally load it down with the trips i go on.

Thanks for the advice comfortzone!

Cheers,

wooly
 
Wooly said:
My understanding is the higher the pitch the lower the RPM? therefore I wouldnt want to go lower then 19? That sounds interesting maybe i will try a 4 blade.

Yes they said optimal rpm is 5300-6300 for WOT.

I dont think my boat is considered heavy though, its actually a very light aluminum when compared to other boats its size and style. However i personally load it down with the trips i go on.

Thanks for the advice comfortzone!

Cheers,

wooly
Click to expand...
you are right, the higher the pitch the lower the rpm, but thats when u increase the same style prop pitch, when changing styles of prop everything changes
I didn't mean to say you had a heavy boat but any way you look at it 6000# is alot of weight to get out of the water...I suggested to stay around the same pitch with the 4 blade because when going from 3 to 4 blade the extra surface area/drag makes it harder for the engine to turn lowering the rpm, but in turn moving much more water then a 3 blade would, making for a more efficient propulsion...I kinda think of it like tires on a 6000# truck, 8inch wide you have the avilable HP, but will be spinning the tires (not efficien...similar to prop slip), put a set of 12inch wide tires on, much more surface area/tration, and the HP is put to use...

btw I owned a 25' cruiser about 6000# loaded...4 blade was the ticket for best ecinomical cruising
 
i would try a 4 blade they are far better. next i would check the height of the motor this can play a big part make sure its not mounted to low.
 
Talk to Ken at Propgods in Florida; of course do it all on his website and he will give you your prop slip and such once he has your info to make sure you are running the right prop; less messing around trying them out; you give him your info and he gets back to you as fast as he can with solutions to achieve what you want. send him an e-mail and he does the math for you! Propgods.com is all you need!
 
I switched to a 4 blade and it has improved my performance big time. I get on step quicker and I can stay on step at much slower speeds than with my 3 blade. It also eliminated almost all my porpoising.

If you can achieve max recommended rpm range at WOT with your usual load with the prop you have,then my experience tells me you will need to drop probably 2" of pitch wen going to a four blade. All the pros informed me that you need to still be able to achieve max range at WOT. If you go 4 blade and keep the same pitch I am pretty sure you will be under RPM and consequentially lugging your motor at any speed. This is not good long term.

I am no expert, but this is what my experience and research taught me last year.

Let us know what you end up with.
 
I went down 2" for eactly the reason you note. You must still be able to reach the recommended RPM at WOT
 
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