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Author Topic:   1988 SPORT 15, Yamaha 60-HP
zotcha posted 06-22-2015 12:57 PM ET (US)   Profile for zotcha   Send Email to zotcha  
I have located [a 2010 YAMAHA 60-HP outboard engine]. I believe it to be a High Thrust model. I am considering purchasing this outboard to install on a 1988 SPORT 15 with a Bob's 5-in-1 manual jack plate. My knowledge of High Thrust does not go any further back than my research of 2005. I was always under the impression that [the Yamaha 60-HP engines designated as High Thrust] were designed for pontoon boats. I have the serial number [of the engine being considered for purchase] for reference of gear ratio.

I am almost certain [the proper shaft length for the 1988 Boston Whaler SPORT 15 boat] is a 20-inch shaft.

[Can readers offer] any help? Should I call Andy at Sim?

The outboard has a stainless steel 13.5 X 15 Solace [SOLAS?] propeller.

zotcha posted 06-22-2015 07:44 PM ET (US)     Profile for zotcha  Send Email to zotcha     
It appears [the engine being considered for purchase which is believed to be a High Thrust model and some other engine which is apparently not a High Thrust model] both [have a gear ratio of] 2.33:1, [and the difference between the High Thrust engine being considered for purchase and some other engine is] just a bigger diameter propeller shaft housing, a larger foot and hub, and a larger diameter propeller [aperture].

As usual, [the 1998 Boston Whaler SPORT 15 is being rigged] for shallow draft and top end performance. Any help appreciated.--zot.

tedious posted 06-30-2015 03:05 PM ET (US)     Profile for tedious  Send Email to tedious     
Zot, I'm not quite sure what question you are looking to have answered. As far as I can tell, you must be looking at a T60, basically the F60 but with the mid-size gear case. The T60 has the same 2.33:1 ratio as the F70, while the F60 has a 1.85:1 ratio.

As the owner of an F70, I would not leap to put a T60 on a Whaler SPORT 15. The larger propeller is [excessive] and is contrary to your desire for shallow draft and maximum top speed. In fact, I wish they made the F70 with the smaller gear case, but I am guessing it is not rated for the additional torque.


jimh posted 07-01-2015 09:53 AM ET (US)     Profile for jimh  Send Email to jimh     
Tim--I think you have figured out the real topic of this thread:

Is a Yamaha high-thrust T60 suitable for use on a Boston Whaler SPORT 15 which is being rigged for maximum speed and minimum draft in preference to the usual F60 model?

[I deleted a portion of this discussion in which the original poster became confused about the shaft length of the engine being considered for purchase but later discovered the shaft length of the engine being considered for purchase was 20-inches, or, at least, that was the impression I got--jimh]

zotcha posted 07-01-2015 10:53 AM ET (US)     Profile for zotcha  Send Email to zotcha     
Thank you gentleman. I was trying to justify a High Thrust model on a 15 Sport. It was a pretty good deal, but I was not sure if I was going to be happy with this application. I will continue to search for an F60 or F70. Thank you.


Peter posted 07-01-2015 01:09 PM ET (US)     Profile for Peter  Send Email to Peter     
I doubt that torque is the reason why the F70 uses the 4.25 inch (2.33:1) gearcase rather than the 3.5 inch (1.85:1)gearcase. More likely the 2.33:1 ratio is used because the Yamaha propeller pitch range for the 3.5 inch gearcase has a lower top speed potential.

With 1.85:1 ratio, the F70's WOT speed range with Yamaha propellers is about 24 to 51 MPH. With the 2.33:1 ratio and the Yamaha propellers, the WOT speed range is about 26 to 60 MPH.

Also, it is more likely that the F70 would be put on a boat that benefits from a bigger diameter propeller, like a Montauk 17, than would be the case for a 50 HP motor.

There were plenty of Sport 15s configured over the years with Evinrude/Johnson and Yamaha 4.25 inch gearcases. I had one with a Yamaha 70 2-stroke and it ran 43 MPH on a Yamaha aluminum prop. Most of the time the conditions were such that I could never run the boat that fast.

I would not pass up a good deal on a T-60 for a Sport 15 just because it has the 4.25 inch gearcase unless you plan on running that Sport 15 at WOT all the time which would be quite hard to do.

zotcha posted 07-02-2015 09:28 AM ET (US)     Profile for zotcha  Send Email to zotcha     
Point well taken. I missed the deal on the T60. That was the type of information I was looking for. I'm going to continue refinishing the hull and keep searching for an outboard. Thank you.


Tom W Clark posted 07-02-2015 10:54 AM ET (US)     Profile for Tom W Clark  Send Email to Tom W Clark     
For a Sport 15, I would prefer a T60 over an F60, unless top speed were your singular goal. The larger gearcase gives you many more options for propellers
zotcha posted 07-02-2015 11:24 AM ET (US)     Profile for zotcha  Send Email to zotcha     
Thank you Tom, how are you? Wish I would have had this response last week. Engine is sold. Eighty hour fresh water 2010 model...
Keeper posted 07-04-2015 11:04 AM ET (US)     Profile for Keeper  Send Email to Keeper     
I have a little over a year now running my F70 on my 1988 15 Boston Whaler. I am extremely happy. I would highly recommend it.
zotcha posted 07-04-2015 12:07 PM ET (US)     Profile for zotcha  Send Email to zotcha     
Are you the member in Az with the custom CC? For $7800 I'd be thrilled too!


tedious posted 07-06-2015 08:29 AM ET (US)     Profile for tedious  Send Email to tedious     
Zot, have you changed your mind about what you're looking for? That is, are you no longer rigging for "shallow draft and top end performance" as described in your second post to this thread?

The T60 will be a bit slower, and be deeper in the water by about an inch and a half, compared to the F60. If you don't care about top speed and shallow draft any more, then a T60 will do you just as well.


tedious posted 07-06-2015 09:31 AM ET (US)     Profile for tedious  Send Email to tedious     
Peter, you're probably right about the F70 not being offered with a 3.5" gearcase being a matter of marketing, not engineering. Over and above the Yamaha prop compatibility, they probably just didn't think they'd sell very many F70s with a small gearcase.

It's too bad, because I think an F70 with the small gearcase would be an outstanding setup for a 15, particularly one used mostly in calm water.

If I hit the lottery, maybe I'll buy an F60 and swap gearcases.


zotcha posted 07-06-2015 11:41 AM ET (US)     Profile for zotcha  Send Email to zotcha     
Tim, if I had not purchased all of the running gear for my F60 in a crate, I think I'd be looking at an Evinrude Etec. I miss the torque of a two stroke, and now damn close to as quiet, no smoke, and comparable fuel mileage.

The problem is, I believe I am only building this boat for resale. So really not sure if I want to power it at all, and leave the power choice to next owner. I just missed a very fair price on a T 60, and was looking for experiences with the larger gear case. Thank you all for the input.


tedious posted 07-06-2015 01:22 PM ET (US)     Profile for tedious  Send Email to tedious     
OK, different story then. I think your idea of selling the 15 without a motor is a good one. Even if you get a crazy good deal on a motor, you'll be lucky to make your money back on it. Better to let the buyer pay for the boat, and then they can eat the depreciation on the motor.

Good luck with it!


zotcha posted 07-06-2015 10:04 PM ET (US)     Profile for zotcha  Send Email to zotcha     
Thanks Tim! I am in agreement. Hope to find someone who will appreciate it. It will soon be ready for a new owner! Thank you for the help.


Russ 13 posted 07-09-2015 11:33 PM ET (US)     Profile for Russ 13  Send Email to Russ 13     
The 15 is a LIGHT boat that is also small.
I would suggest a LIGHT outboard, say a 70 two stroke, or new four stroke. Some of the older 60 and 70 HP
four-strokes were heavy for such an application.
When the hull was manufactured, there were no four-stroke heavy outboard available.
JP3 posted 07-14-2015 09:00 AM ET (US)     Profile for JP3  Send Email to JP3     
Russ 13,

Take a look at the new 4 strokes...

My Original Mercury 2-stroke from 1987 weighs 280 lbs. The 60 HP command thrust that I plan to mount on the transom weighs 260 lbs. The Yamaha F70 weighs 257. (Both are lighter than the original.)

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