Propeller selection

[Bad Habit]

 I need a new prop for my boat this year. I can't read the numbers on either prop I have now. There's nothing in the manual that came with the boat. What's the best way to know the recommended prop for my boat. It's a 25' Regal, 260 hp 350 Chevy with an Alpha 1 outdrive. Any help would be appreciated.

[guffins fisherman]

It's not foolproof, but I believe Mercury has a prop selection tool on their website.  Since you're running a Mercruiser drive, they should have what you're looking for.  I am sure you could give them a call too.

 

Matt.

[Bozeman Bob]

Your going to need the maximum rpm's that the engine gets  at wot with a average load on board.  Then read the tag (usually )on the valve cover to see what the max rpms are ,probably around 4400- 4600 for that motor if memory serves me right. At this point you can take your old prop to a prop shop and get there recommendation.  Or try wire brushing the outer hub where the retaining nut rest on. The numbers are  normally stamped there. The most common pitch for that setup is 19 "  or 17 " and the diameter probably in the 15+ - range. So If you have a 19 and are hitting 4,000 rpms you would go down to a 17" pitch with the same diameter to get your rpms up to the recommended number. And that number is key, so that your not constantly lugging the engine if over pitched or revving it too high if under pitched. Basically if you want to skip the prop shop we need the rpm number and what's on there now. I have never seen a prop that isn't stamped ,so do some wire brushing or scraping to locate it.

[Mike M]

Work with your local prop shop. My local shop actually let me try a couple props. You could offer a cash deposit in case there was damage to a prop your trying. I bought a used boat that had the wrong prop on it. When I finally got the right prop on the boat OMG! what a difference!! 

[HB2]

I went to Spinelli in Rochester when I bought my hardtop back in 1987 to get a spare . 

 

Sat down with the old guy there and explained my boat . 

 

It came with a 15 x 17 . 15 diameter 17 pitch. 

 

His recommendation was to go to more of a power prop than the speed prop it came with   because of the extra weight of equipment etc. 

 

So I bought a 15 1/2  15. He was right . 

 

Boat comes out of the water better with load and is better in rough seas as it does not lunge forward when on plane . Trolls better also . 

 

I lost a little top end but it's a fishing boat so I really don't care . And I can't over rev  it . Probably what should have come with it . 

[jth21usa]

Can you find the original manual? It’s sometimes in there. Were you happy with the prop that was on there?

[rolmops]

https://www.miwheel.com/outboard-propellers/outboard-sizing-analysis/

Edited February 10, 2020 by rolmops

[Bad Habit]

I can’t find it in the manual but I’ll check out the miwheel site. Thanks.

[sherman brown]

just go with a 19p or even a 17p high five and you'll be very happy. when I got my boat and loaded it for erie it took forever to get on plane. I replaced the 19p 3 blade prop with a 19p high five and it jumped out of the hole gave me more control in rough water it held plane at slower speeds its just a much better all around prop. but I only have a 21' boat with a 350 mercruiser. you might be better with a 17p with a 25' boat.