New to club Yamaha

[5150abf]

Repowering with a new F50.

My beloved '81 Evinrude has finally run its coarse and it was time for repower, always wanted a Yammy.

Need to order prop Monday and I don't have a clue what to get.

I have spent time on the prop finder looking at similar boats but seek input.

I am running an '80 Sea-Nymph 16' aluminum, length is 16' 6'', beam is 68'', I am thinking she is right about 1000 lb but that is a complete guess.

Redid it a couple years ago with new 3/4 marine ply, full bottom deck and front and rear casting decks so there is almost 500 lbs of just wood in her.

Love the boat itself, made a camper top for it, all the wells are lit, Roswell speakers with a 400 watt amp, rod holders, just the way I want it.

Old prop on the Rude was a 12 1/4-13 pretty sure but would that transfer to a four stroke?

I am going with an aluminum prop, I river fish and if I whacked a stainless prop I think I would puke.

I am an aluminum welder by trade so I can fix an aluminum one, not that I hit stuff a lot but it is always an option as you know.

Also wondering if I will get a little more top end with the new engine.

Old one would run a respectable 28-30.

New engine is 50lbs heavier so I would think probably not.

And yes my transom is good, new 4-5 years ago, 2 sheets 3/4 ply marine wood, gorilla glued and screwed

Thanks for any input
.

 

[99yam40]

did you look at this web site to see what prop they used of some rigs close to yours?
probably need to know what the rig weighs, not just guessing
https://yamahaoutboards.com/en-us/home/owner-resources/all/performance-bulletins

 

[5150abf]

So just went through the prop selector on the Yamaha site and the closet boat to mine they are calling for a 11-5/8x11.

The old rude was running a 12 1/4x13, why is the new one so much smaller.

Granted the new motor will be turning another 1000 rpm but just seems to be too small.

Any thought?

 

[racerone]

What are the gear ratios on the 2 motors ?----Or do you think that does not matter ?

 

[Sea Rider]

Why compare both engines, both are different ones. How many Yam OEM props sizes are available for that 50 HP ? Factory delivered OB's with a prop are usually medium size props. Pick the middle size and drop at least one pitch down.

That will be your starter prop, will need to go for a wot spin as usually loaded and check max achieved rpm, can fine tune from there whether wanting best hole shot or best top end speed. Usually will need to invest some money as it's impossible to dial top prop for your boating requirements on first attempt, and that's from experience.

Happy Boating