prop size

back again, iv'e got a yamaha 40hp HEO do'es anybody know the size and pitch of the original supplied by yam. the prop thats on is unknown make and is 10.5 ins which seems small. it's to push a redbay 166 fastfisher,can anyone with the same type of set up help please, she's the same as a strikeliner size and hull.I know yam props start at 11ins for that size outboard but the pitch and size im in the dark. be grateful for any advice. only getting 10mph so not good. fingers crossed hoping . cheers paintwise. would thank everyone but cannot find how to on site.

do you know the year of manufacture
Have a look here http://www.boats.net/parts/search/Yamah ... parts.html
http://boatpropellers.iboats.com/?cart_ ... =075736419
http://yamahaoutboards.com/owner-resour ... rs-manuals

propping a boat right is a black art, but 40 hp props can be 10" or 10 1/4 ". You need to know the size and pitch and it should be stamped on the prop such as 10 x 14 or even 11 x 14 .... Size 10 - 11 isn't too much of a big deal, the pitch is more important, too little and you'll over rev the engine, too much and you'll put the engine under some un-required strain. However a change of prop isn't going to give you much more speed maybe 6-8 mph max, unless the prop that is on it is bust and you have spun hub issue (google it) with your prop.
If not a spun hub issue then I think you're engine isn't running right , hence your slow speed.
Start up your engine and pull off the spark plug wires one by one. Your engine should show a decrease / drop in power. if it doesn't or if it stalls then you have a power issue.

As they guys have said, propping a boat is a black art, and expensive We would need to know you Diameter and pitch first and then we can go from there. I would say the 10.5 is your diameter.

Also, as above, it is worth checking that the engine is running well.

thank,for the replies lads, got the prop off today, it's a 10and half ins 12pitch G prop with seems small anyway for a planing hull. been to web been told 12 to 19 so still none the wiser. got a tachometer in the post so should know more about the rev's later. must be somebody with a 40hp lump and strikeliner out there. thanks again for the help. paintwise

Have you contacted Redbay boats http://www.redbayboats.com/contact-us they should be able to tell you the size of engine and prop requires to push the boat

Hi
I had a Redbay fastfisher 166 that I bought from new in the 90's. She had a Yamaha autolube 40hp 2 stroke and it flew like a bird even with 3 anglers aboard. 20 knots on a calm day. So the engine size to boat is not a problem. If my memory is right they are rated from 40-60hp.

Have you had the engine checked out for a major problem as some of those Yamahas drop to low revs as a safety if there is a problem with oil pressure?

Hope you get sorted.

Caz

paintwise, here just to say a big thank you for all the advice and contacts you good people posted. narrowed problem down to engine, and I am getting that sorted thanks again, and keep up the good work. paintwise.

Good to hear you're on the way to a solution. When you get there, dont forget to post what it was, every bit of info and experience adds to the site's communal knowledge bank. We're all learning...

what do you reckon is the issue with the engine paintwise.

is it down on power ?