prop identification

[drunk pirate]

Recently got a new (different) boat. 1987 Baja Force 235 cuddy weighs 3250 lbs, has 454 mag 330 hp alpla one, running I think a mercruiser prop part # 48 73982 A4 21P. obviously a 21 pitch prop but what about the rest of the info. My number's not listed among the websites. I got about 58mph with this prop at 4400 rpm's.
Another prop came with the boat a michigan wheel 14 1/4 x 22. which one would be better ? I would think this boat would do better than 58 . Thanks

 

[hwsiii]

Re: prop identification

Dual Post

 

[hwsiii]

Re: prop identification

THe 13 3/4" x 21" mercury prop you are using now at 4400 assuming WOT is 4500, as it almost maxes out the RPM. The 14 1/4" x 22" will lose a bunch of RPM because of the change in Diameter and Pitch. Approximately it will change the RPM to about 4000 if it is the same model and series of prop. But either way you are going to lose speed if they are both stainless. But give it a try anyway, you have nothing to lose. If it is a 1.47 gear ration it will go down to about 3,900.
H

 

[drunk pirate]

Re: prop identification

Thanks for the feedback, how were you able to decipher that part number? I don't see a 13 1/2 any where in there. Is there a part list somewhere I couldn't find ? Do Mercruiser props then start with that 48 number ? Thanks again Great site, I enjoy reading here even when I'm not trying to figure stuff out. Lots of good info. I think WOT is 4600. Both props are 3 bladed stainless.

 

[hwsiii]

Re: prop identification

Just put this number in Google 48 73982 A4 21P.

H

 

[boat1010]

Re: prop identification

I have just about the same size and weight boat. Mine is a 1989 Arriva 24ft with the 454. I think mine is only 300 hp I carry 70 gal of gas. With just me in the boat and about 1/4 tank of fuel I can get almost 60 out of it. I run a 23p on this boat. I have had two of these boats. Identical. One was fuel injected and the one I have is carburetor. Everyone says the fuel injected is the best. I could only run a 21p on the fuel injected boat. It would only run about 55. Both were running WOT at about 45 - 4600 RPM I do not know if there was a difference in the lower units.

 

[drunk pirate]

Re: prop identification

Thanks for the input. I tried punching that # into Google but with different combinations of oem part number, mercruiser etc. 58-60 mph huh ? I guess I'll try on the 14 1/4 x 22 Michigan wheel and run it up to 4600 and see what happens. I was hoping for mid 60's at least. Thanks

 

[boat1010]

Re: prop identification

It starts getting pretty hard and expensive once ya get to 60 with a boat our size. A few MPH gets pretty costy. Either with engine mods or gears or props.

 

[boat1010]

Re: prop identification

Recently got a new (different) boat. 1987 Baja Force 235 cuddy weighs 3250 lbs, has 454 mag 330 hp alpla one, running I think a mercruiser prop part # 48 73982 A4 21P. obviously a 21 pitch prop but what about the rest of the info. My number's not listed among the websites. I got about 58mph with this prop at 4400 rpm's.
Another prop came with the boat a michigan wheel 14 1/4 x 22. which one would be better ? I would think this boat would do better than 58 . Thanks

If you are only running 4400 WOT with a 21p you probably won't do any better with a 22p That is going to take your WOT RPM down.