Is Yamaha 115 4 stroke enough power for a 73 Seafari ?
 

Guys, I need some opinions.
I currently have a 1986 150 Yamaha that just bit the dust and need to re-power. Have a great deal on a 2016 Yam 115 4 stroke but need to know if that will be enough power. I keep it mostly to bay fishing and occasionally in the ocean ,but mostly inshore. Most of the time its just me and a friend. Any advice? Thanks to all.

Forgot to mention that it is a 73 20 ft Seafari

If you get either Gillie or Ken Reeves (PropGods) to dial your wheel in I believe you would see something like -
Minimum planing speed - 15 Mph
Cruise Speed - 20-24 Mph
WOT - 33-35 Mph
You'll probably be well north of 3 mpg.
If that would be suitable for your use, you will be happy with that motor. Have it serviced regularly and it will treat you right.

Thank You Terry
 

Thanks Terry for the info. 30 to 35 is as fast as I need. The 86 150 topped out at 44 mph and I rarely ever went WOT.

I am just one "Data Point" and I'm sure others will respond shortly. There are a few here like me that run 90's on the 20 footers and I think "Tiny" has a 90 on a SeaFari. The nice thing about the 90's or 115's is you don't blow the beer out of your cup on the way home! You can sit back, motor along, steer with your feet and tell extremely "tall" fishing tales.

Balance and min plane speed are some of our favorite friends.

Engine weight is more important than power on the 20' hull. Back in the 60's and 70's many were sold new with 85 hp motors (rated at the powerhead instead of prop!) Most folks have no idea how efficient the SeaCraft hull is! Modern hulls need lots of beam at the transom to handle the weight of a 4-stroke motor, so they have more drag, require more power and don't ride nearly as well as the relatively light and slender SeaCraft! That's why most folks today think any 20' boat with less than 200 hp on it is underpowered! The 19/20' hull was designed in the mid-60's for the biggest motors then available, the I-6 Merc and V-4 OMC's, which weighed 300 lbs or less. Ran my Seafari for 31 years with a 115 hp (~100 hp at prop) V-4 on the transom. With a light motor and trim tabs, you can ride very comfortably SITTING DOWN in 2' square waves at ~12-14 mph. With a heavy motor on the transom, it's harder to plane that slow and the boat won't run as flat so it won't ride nearly as well. That said, at least the Seafari has more weight forward than the CC models, so it tolerates a heavier motor a little better, plus the extra hull stiffness provided by the bulkhead, cabin top and coamings will make it feel more solid.

Thank you Bushwacker.Good info . I had my Seafari since 1978 and love the ride! It will outlast me!

I've got Father Franks old boat. It's still got a 90hp optimax, which is great. It runs well. It's very economical. Happy with it for sure. PS optimax is heavy, we keep the plugs in, but that doesn't bother us. The boat is all original.

Skipper T and Bowrider have a 19 with a 115 ETEC.
The balance is perfect.
The ride is envious.

Not a hot rod.
Just right.

Thanks to you all !
 

I am going with the 115 Yamaha .Would you guys recommend a good prop that would be suitable for general use? Not using the boat for skiing, so its just to get up and go cruising mostly.

I have a 72 Seafari. Old 115 tower. I'm using a classic mercury black max aluminum. 13.75" x 15. I can't help but praise this simple classic prop. Powertech makes a clone in stainless. MQF 3. I'd steer you there. PT Props also makes a Yamaha semi-cleaver clone called the SCD in a 3 and 4 blade. Smaller diameter 13 inches, I think.

I would suggest you borrow a mercury black max/ quicksilver black diamond, in 13.75 x 15 at a local shop and see how it performs for you. That prop is available from $80 to 130 w/hub everywhere. Anyone selling props should have some on their wall. easy loaner. If you're pleased, get the PT MQF3 in the same config.

Perhaps the best 3 blade sternlifting design, it will get the Yamaha up quickly and let the hull impress. Easy to turn due to low cup makes for great holeshot. big blade and shape gives great stern lift.

My .02...

Thanks,Mc
 

I will take that .02 and spend it wisely!

I run a 4 blade aluminum Solas Amita 4 in 15" pitch on a Yamaha F100. Works great. I run shorter gears in the lower unit than the F115 so it should be perfect for that OB as well. Just faster. 31 MPH without t top. 29 with. You will be in the low to mid 30s. The 17 is no faster. Kills hole shot, but better MPG. Harder on the motor.

Typing on a phone so if I sound curt, that's why.

They are $100 online.