Prop for Seafari 115 Merc I-6

[McGillicuddy]

Anybody have any knowledge of this ss prop. I have no other info but the stampings you see... It's 15 spline and led to believe its for Force or Mercury. Are those typically interchangeable? I know the pitch is maybe a bit high at 17 but thought the cleaver shape would give me some stern lift (or is that a misguided belief) Fr. Frank?

[lost2a6]

Looks like a old style Yamaha prop.

[ripndip]

Mcgill I agree with lost, it looks like the "black stainless" yamaha prop cleaned of paint and with a new hub. I think these props are still available new.

[Fr. Frank]

This prop looks like an early (mid 80's) Yamaha SWS series with the black teflon coating removed, and can be easily re-hubbed for Mercury inline 6 motors if it's not already. This is a good stern-lifting prop.

As to being the right pitch, what's your current lower unit gear ratio? What year is your Merc 115? Does it have the original lower unit?

Give me your current gear ratio, or current performance (prop type, diameter and pitch, current max rpm, top speed, time to plane, etc.), and I'll can tell you your current gear ratio, and give you some suggestions for good props for your motor setup, as well as some tuner tricks for your installation.

I have a newer 90hp Optimax on my '72 Seafari, (actually developing 111 hp/5450 rpm at the prop as just tested), and currently run a 13"X21"P prop. It's an Apollo, and for the Seafari it's really a lousy prop, but I can't afford the new 4B 12.75"DX20"P PowerTech prop I want.

[McGillicuddy]

Thanks guys.
In my shake down cruises with a light load I've determined that I am topping out @ 4400 rpm making 33mph by gps.
I seem to be getting on plane at about 12-13mph @ about 2500 rpms (not certain of this but close) but have not timed the rise from a dead stop to WOT. I also have a Stingray hydrofoil on it which I think is very helpful, although I have not tested it w/o. I got about 2.5mpg off a 6 gal test tank.

I finally determined the Al prop to be 12-3/4 x 21 R MWC. I have not removed it so I'm not sure if it has a model number on the inside.

The motor is an '83 Merc 115 I-6 with a 20" shaft that appears to be original. The gear ratio should be 2:1.
The motor is in very good condition with slight damage (not sure of the term) to the edge of the top piston. I believe the timing has been retarded to 21deg and the jets have been changed to better serve the upper cylinders with modern gas. For now I'm running 50:1 QS premium plus

The motor certainly pushes the load effortlessly with 2 guys 30gals and no gear or bait tank(I'm hesitant to fill the bait tank until I redo the scupper with new tubes and vortex).

I was thinking I might pay $70 or so for that Yamaha prop. What does it cost to change a hub if necessary? And How inexpensively might I find a more fitting used prop? Here some pics of the current situation. Thanks again for the expertise, guys.

[Fr. Frank]

Here in on the west coast of central Florida, a rehub will cost you $60. If the prop will already fit your propshaft, you don't need a rehub, just the right thrust washer, and propeller nut and washer kit.
Based upon the rpms you're getting now with the 21P, I'd venture that the 17P is about right.
As for price of a used prop, you can't do much better than the $70 you mentioned.

What I want to know is where to you put all 30 of those women, and if they're midgets or something

[seafari25]

hahaha Fr Frank!

I get it.

[McGillicuddy]

Thanks Fr. Frank. I failed to attain that prop (got out bid @ a c- note budget) so I'm still looking for advice. I know you mentioned the powertech M series but I don't have 3 bills right now. And as far as fitting 30 gals on a Seafari, well here are the ones that stayed on for the evening cruise...

[rhody98]

if that's a seafari, them are midgets.......

[McGillicuddy]

Come on... They're petite...