correct prop size for boat ??

[truckermatt]

hello,

I recently picked up a 1990 Wellcraft Eclipse 186 bowrider. 4.3l mercrusier.

When i took it out i had recorded 43 mph on GPS and 46 on speedo, @ 4700 rpm's

i have a 14.25x 21p 3 blade aluminum prop on there now....

are these numbers OK, because i am buying a spare prop and want to know what to get...

The boat gets on plane alright and i use it primarily for water sports and cruising.

 

[countvlad]

Re: correct prop size for boat ??

hello,

I recently picked up a 1990 Wellcraft Eclipse 186 bowrider. 4.3l mercrusier.

When i took it out i had recorded 43 mph on GPS and 46 on speedo, @ 4700 rpm's

i have a 14.25x 21p 3 blade aluminum prop on there now....

are these numbers OK, because i am buying a spare prop and want to know what to get...

The boat gets on plane alright and i use it primarily for water sports and cruising.

Im not sure whats the recomended range for that motor but 4700 sounds bout right....i think ur on the right track

 

[hwsiii]

Re: correct prop size for boat ??

Matt, if you are having any problems pulling people up for skiing or tubing you might look into getting a 4 blade propeller 19" pitch for using when you are doing watersports. You can buy a Solas aluminum 4 blade prop on Iboats pretty cheap. If you are not having problems just get what your already have, 4,700 RPM is right at the top of the recommended WOT range right now.

H

 

[MikDee]

Re: correct prop size for boat ??

hwsiii,

Oops! Guess I wasn't awake yet when I first made this post, I deleted it, I thought you suggested a 21" pitch-4blade? Sorry :redface:

Now, (in my best "Maxwell Smart" voice) Would you believe? Just trying to keep you on your toes

I totally agree, a 19"-4 blade alum seems just about right!

 

[sleeper]

Re: correct prop size for boat ??

normally you just drop 1 pitch for a 4th blade when using the same material prop. a 17p prop will cause an over-rev for sure. If you use it for watersports and cruising, keep your current prop for cruising and get a lower pitch for watersports. a 19p 4-blade aluminum would be good for watersports. Just watch your rpms when lightly loaded.

 

[hwsiii]

Re: correct prop size for boat ??

Mik, my program says he will gain over 800 RPM going down 4" to a 17" prop and he is already doing 4,700 RPM, so if I deduct 200 RPM for the fourth blade that leaves him with 600 RPM plus the 4,700 RPM equals 5,300 RPM he would be turning and that is too high in my mind. Do you think i made a mistake, please tell me because I certainly don't want to give people wrong information.

H

 

[hwsiii]

Re: correct prop size for boat ??

LOL Mik, like I told steele the other day, I NEVER make a mistake UNLESS I am breathing.

H

 

[MikDee]

Re: correct prop size for boat ??

LOL Mik, like I told steele the other day, I NEVER make a mistake UNLESS I am breathing.

H

Great response!

 

[hwsiii]

Re: correct prop size for boat ??

Thanks Mik. You and steele both have a LOT of knowledge and I am always trying to learn more so I always read what y'all post. We all are just trying to help the people that come here, although I will have to say I am adding to my database and trying to refine my program as well. But so many people just get answers and you never hear back from them how everything worked out.

Now, (in my best "Maxwell Smart" voice) Would you believe? Just trying to keep you on your toes LOL

H

 

[truckermatt]

Re: correct prop size for boat ??

i havent pulled a skier yet, but the boat gets up pretty quickly, but it has some bow rise.... but i may be installing smart tabs soon...

I dont want to over rev my engine too much..... since it works and run so well now, i will probably just go with what i have already...

 

[truckermatt]

Re: correct prop size for boat ??

if i get a 4 blade 21p prop will my rpms drop at WOT....

also will i gain holeshot?

 

[hwsiii]

Re: correct prop size for boat ??

Yes they will and you will gain holeshot.

H

 

[truckermatt]

Re: correct prop size for boat ??

so a 4 blade 19p prop should keep my rpms at around 4700 WOT and inprove holeshot?

how much top end would i lose?

 

[hwsiii]

Re: correct prop size for boat ??

Matt, just buy the prop listed below and you will lose some RPM and a probably a couple of MPH but you will gain holeshot and puling power.

http://boatpropellers.iboats.com/Mercruiser/155_-_210_HP_(All_Years)_21.00-Pitch_Amita_1513-140-21_Propeller/765/9582/?**********=714247613&*******=215886655

Iboats
Price: $103.99
You Save: $43.01
Compare: $147.00
Discount: 29.3% Off
Add Amita Aluminum Propeller 1513-140-21 To Your Cart

Propeller Specifications:
SKU:#1513-140-21
Manufacturer: Solas
Brand: Amita
Material: Aluminum
Diameter: 14?
Pitch: 21?
Blades: 4
Rotation: Standard (Clockwise)

H

 

[truckermatt]

Re: correct prop size for boat ??

thanks for the info, If i went with the 4 blade 19p... would i lose any rpm or speed..... coming from a 3 blade 21p??

 

[MikDee]

Re: correct prop size for boat ??

Matt, just buy the prop listed below and you will lose some RPM and a probably a couple of MPH but you will gain holeshot and puling power.

http://boatpropellers.iboats.com/Mercruiser/155_-_210_HP_(All_Years)_21.00-Pitch_Amita_1513-140-21_Propeller/765/9582/?**********=714247613&*******=215886655

Iboats
Price: $103.99
You Save: $43.01
Compare: $147.00
Discount: 29.3% Off
Add Amita Aluminum Propeller 1513-140-21 To Your Cart

Propeller Specifications:
SKU:#1513-140-21
Manufacturer: Solas
Brand: Amita
Material: Aluminum
Diameter: 14?
Pitch: 21?
Blades: 4
Rotation: Standard (Clockwise)

H

Wow, That looks like a great prop! Especially for that price!

thanks for the info, If i went with the 4 blade 19p... would i lose any rpm or speed..... coming from a 3 blade 21p??

You may, or it may be even better,,, That prop is excellent design, I see why it's a best seller.