1985 Bayliner, need help on prop size

[rodimusprime]

I just recently purchased a 1985 Bayliner Sierra Sunbridge. The boat is approximately 25 feet long and weighs around 5500 pounds. It is the cabin cruiser model. The boat is powered by a 305 volvo penta motor. The boat doesn't have a prop installed at the moment. Does anyone know what size prop the boat takes. I was told the boat would run around 40 mph. Is this possible for a boat this size? Thanks for any help.

 

[gcboat]

Re: 1985 Bayliner, need help on prop size

I THINK they came with a 15-1/2 X 15, non cupped. Give a local dealer a call or better yet call Bayliner @ 877-861-6494. You will need your HIN - she will ask for it to reference. And no, that ole' gal will never see 40 m.p.h. with that 305 in it. Might get close but no cigar on the big speed.

 

[oops!]

Re: 1985 Bayliner, need help on prop size

yeah....props can be pretty tricky......

lots more than meets the eye......

after you do what gc suggested ...so you know where to start...see if you can find a prop shop that will let you try a few different ones.....check out the props forum and start reading......you want highest speed at wot while still getting a good hole shot. and unfortunatly...to get one you gotta loose the other.

 

[BAYLINER185]

Re: 1985 Bayliner, need help on prop size

I have a 93 Ciera 2755 that will do 45 MPH!

I have a 15 X 21 on the boat and it hauls really nice. Everyone I talk to says thats really fast for a boat that big. With the right prop I dont know why you couldnt get close to 40. I have a 300 HP 7.4 though keep in mind so maby youll be able to top aout around 35 with the 305.

Id problably start with a 14 X 19 and see what that does. Once you know what your WOT RPM is with that, then you can then start working prop size out from there. I tried a SS 15 X 21 on ym boat and it was terrible. So yes there is a lot of differances in props. Size Vs cupping and things like that. Youll read alot about of these differances in the prop forum.

 

[tonyg11780]

Re: 1985 Bayliner, need help on prop size

I know that when dealing with prop size, the MOST important thing is what RPM your running at WOT. If you arent running high enough rpm, you are bogging your engine down more than likely. And you dont want to overrev the engine. Most inboard/outboards want to run around 4800-5000 rpm at WOT. If you install a prop and it will only run 4300, you need to downsize the pitch. If you install a prop and it runs 5300, you need to go up about 1 to 2 pitchs. Typically, 1 pitch will raise or lower the RPM around 200 RPM. Hope this helps...and happy boating!

Tony