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Author Topic:   Experience with 15' Classic Hull/60 hp Yamaha 2-Stroke?
Peter posted 06-02-2003 07:39 AM ET (US)   Profile for Peter   Send Email to Peter  
I am exploring repower options for a 1987 15' Super Sport. I have a brand preference for Yamaha because the service network is very strong in my area and I have narrowed the choices down to four power plants: F50, F60, 50 2-Stroke or 60 2-stroke. Of the 4 choices, only the F60 exceeds the expected maximum transom weight (I figure about 235lbs at the time the 15 was designed), by about 15 lbs.
At the moment I am heavily leaning toward the 60 hp 2-stroke model because I cannot justify spending an extra $900 for the F50 and $1,400 for the F60 (I don't troll much, noise and smoke don't bother me and I have figured that it would take at least 700 hours (14 x 50 hour seasons) to recapture the price difference in fuel cost savings at $2.00 per gallon versus the F60).

I am a somewhat concerned that the displacement on the 60 2-stroke is a bit on the low side (51.6 cubic inches) as compared to the now discontinued 60/70 OMC (~56 C.I.) and Mercury (~59 C.I.). Therefore, given my interests and concerns, I would like to hear about any experiences with a 60 hp (or 70 hp) Yamaha 2-stroke on a classic 15' hull.

jimh posted 06-02-2003 08:55 AM ET (US)     Profile for jimh  Send Email to jimh     
I have a pair of 70-HP Yamaha 2-strokes. I think they are the same displacement as the 60-HP version. The pair give a good account of themselves with my 20-foot Whaler hull. I was surprised to learn of their relatively modest displacement. They are nice engines. They start and run well, and they don't seem to smoke too much.

I have often thought that one of them would be ideal on the transom of my 15-SPORT. I am sure the 60-HP version would be a good engine for that boat, too.

There is a chart of crankshaft speed versus boat speed for my 15-SPORT with a venerable Mercury 500 (50-HP) on the transom; see

jameso posted 06-02-2003 09:19 AM ET (US)     Profile for jameso  Send Email to jameso     
I ran a 50 HP Yammie on a 15 CC good rig, do not have a lot of performance figures. My top end was 32/33 MPH. Craft was stable with good handling, no 'chime walk'.
IMHO the best engine for the 15 is an OMC 50 or 60HP two stroke twin, I have one on a mid 80's vintage 15 sport that will top out at 37/38 and the hole shot will scare ya.
Enjoy the boat.
Jim Armstrong
Bertramp posted 06-02-2003 09:45 AM ET (US)     Profile for Bertramp  Send Email to Bertramp     
I just sold a 1976 15 sport that had a merc 50. I found the speed to be around low 30s and boat performed well. I replaced the sport with a 1984 center console with a Yam 70 .... seriously fast boat ...maybe more than what is really needed. I have run a 1984 center console with a 60 yam in Fla and have found that to be probably the best compromise.
where2 posted 06-02-2003 12:33 PM ET (US)     Profile for where2  Send Email to where2     
Thinking about the typical setup through the dealer, the dealers mounted the battery, and the fuel tanks between the rear seat and the transom. If you bring along a cooler, do you put it in the front, or behind the rear seat?

An extra 15lbs in the stern is like a reasonably well stocked cooler. I'd shift some weight around the boat and balance the extra 15lbs on the stern.

Having met an F50, and gotten to know it quite well on a different hull, I have decided if I ever have to replace my 70Hp Johnson, it will be with a Yamaha 4-stroke, F60 (or a 70hp if they ever get around to making one...).

Buckda posted 06-02-2003 02:00 PM ET (US)     Profile for Buckda  Send Email to Buckda     
Peter -

I have a 70 HP Evinrude on my 15' GLS - let me say: a 60 HP should be plenty fast (high 30's).

If I had to repower mine for the long haul, I'd get a 2 stroke 60 or 50 for it, as the next engine on this boat will probably serve as the engine that my (yet to come) kids will use...If the 70 is still around, I'll have to look into figuring out a way to put an inhibitor on it...there's no way that a 15 foot hull with 70 HP is appropriate to a newbie to boating. Significant chine walk and serious hole shot...she's a ton of fun, but can get out of hand in a hurry if you're not paying attention. I would think that a 50-60 HP would be the ideal engine package.

Interesting that this hull does not seem to need the max HP rating for owners to be happy with the performance.

lhg posted 06-02-2003 03:39 PM ET (US)     Profile for lhg    
Peter - Without sounding like a broken record, remember that the Yamaha F60 is a 100% Mercury powerhead, but without the EFI.
The two engines have the same cost. I would think that if you decide in favor of a 4-stroke 60, the Mercury version would be the one to get.

So that if you did opt for EFI over carbs, the Yamaha dealership network in your area could still service it. And I'm sure Mercury dealers could service the Yamaha F60 also.

But I also agree that a 2-stroke 60 sounds like an awfully attractive deal.

chrisb posted 06-02-2003 08:24 PM ET (US)     Profile for chrisb  Send Email to chrisb     
Last year I sold my johnson 48 spl to buy a used evinrude 70 just to get any 170 lb + skier out of the water on one ski. IF you never slalom you can go less, but if you ever have anyone who wants to have fun on one ski you must go 70 imho.
wayne baker posted 06-03-2003 08:20 AM ET (US)     Profile for wayne baker  Send Email to wayne baker     
My brother in law did the same thing as chris said above. He had a smaller motor that worked great pulling his kids when they were young but when his son hit 16 or 17 and wanted to slalom ski he bought a newer larger motor. He put a johnson 88 spl on his. I think I would stay with the three cylinders my self. As a matter of fact that is what I am trying to find in the used market now for my 15.
Roarque posted 06-03-2003 08:32 AM ET (US)     Profile for Roarque  Send Email to Roarque     
Peter, the 60 hp is the best choice. Pay close attention to the mounting of your new engine on a 15 ft Whaler. Read the posts in this section on the right setting of the engine. Up or down one set of holes can change your ride and your top speed dramatically.
Clark Roberts posted 06-03-2003 08:33 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Peter, the 2 stroke Yamaha C60 (no oil injection-51 cubic inches-2.3:1 Merc lower unit) is a good match for the 15 hull. I just propped one for my neighbor and decided on a 15" pitch Stilletto (sp?) and she will turn 5900 at WOT and approx 40mph (engine rated at 6000rpm). The latest Yamaha catalog doesn't list this engine? Also the 2 stroke 60 Merc (oil injection-59 cubic inches-1.64:1 lower unit) is a super match for the 15 hull. Happy Whalin'... Clark ...Spruce Creek Navy
Peter posted 06-03-2003 08:42 AM ET (US)     Profile for Peter  Send Email to Peter     
Thanks Larry, I'll keep that in mind. Certainly an EFI system is better than carburated system.

However, one other factor to consider in the Mercury EFI four-stroke 60 versus Yamaha F60 competition is resale value and in this area of the country, in my opinion, the Yamaha would command a higher resale value than the Mercury. So I would probably still go with the F60 (assuming I went 4-stroke which is not very likely), even with the EFI advantage going to Mercury and the price being the same.

It has been my impression over many years that Mercury has just never had a real strong market presence here. This area used to be dominated by OMC, and is now dominated by Yamaha with Bombardier and Mercury very distant second and thirds. It is my observation that on all of the outboard boat transoms in the two harbors that I operate out of, Yamaha outnumbers Mercury by a factor of 9 to 1 or higher and Yamaha outnumbers Bombardier by something like 5 to 1 (Note: these are casual observations, not a carefully orchestrated market survey). I rarely see a new Mercury on the transom of an older boat, but I do see new Yamahas on the transom of boats I know have formerly had OMC and Mercury outboards.

The majority of new Mercury motors that I do see in my area are typically on the transom of new boats manufactured by Brunswick, such as a Whaler and Bayliner. But for the tying arrangement they have so artfully constructed to effectively take away choice, it is likely that consumers in this area would choose to power such boats with Yamaha or Bombardier products. However, through the tying arrangement, Mercury has probably forcibly gained some market share in this area.

Peter posted 06-03-2003 09:36 AM ET (US)     Profile for Peter  Send Email to Peter     
Thanks Clark. I like the fact that the Mercury has more displacement and seems like it might be a very good fit for the 15' hull. However, I think I'm just going to end up being one in the crowd of many here for this repower project and stick with Yamaha.

I didn't see the C60 in the catalog either but is it still available? If it is still available, is the only difference that it doesn't have oil injection or does it have also have a bigger "foot" like some of OMC's commercial products did? The consumer 60 has a gear ratio of 2.3:1 also so I suspect it is the same Merc lower unit.

Clark Roberts posted 06-04-2003 10:03 AM ET (US)     Profile for Clark Roberts  Send Email to Clark Roberts     
Peter, I don't know if C60 is still avail as a 2003 model! The foot is a Merc (same as the 75/90Merc with a 2.3:1 ratio while the 60 Merc uses the smaller 1.64 and 1.83:1 ratio lower units as on the 40 & 50 Hp. The 60 Merc lower unit, being smaller (except for the BigFoot model which uses the above 2.3:1 ratio unit),offers reduced drag and less draft... an important factor if you boat in skinny water like I do... Whatever you choose, if you maintain it well it will serve you well. Happy Whalin'... Clark... Spruce Creek Navy
RichAA posted 06-05-2003 04:02 PM ET (US)     Profile for RichAA  Send Email to RichAA     
Peter, I have a Merc 40 on mine and it's plenty of performance for me, my wife and 2 young kids. I've gotten a slalom skier up, but it's hard. You'll have a fast boat with any of the motors you listed.

Good luck!

Spruce Creek Navy, Minnesota Chapter

jonha posted 06-08-2003 02:52 PM ET (US)     Profile for jonha    
just repowered my 15ss with merc 50 4 stroke efi.
good power. i happen to love the quiet and low running speed. sure your 60 hp will really move that 15. good luck. jonha
Toad2001 posted 06-18-2003 01:46 PM ET (US)     Profile for Toad2001  Send Email to Toad2001     
Hi Roarque,
I plan to install a new Honda 50 very soon on my 89 15' GLS. Its a long shaft with power tilt/trim.
I assumed it would be mounted with it's bolts lined up in the lowest position, engine somewhat resting on the top of the transom. Is this correct? I want maximum efficiency and speed.
Also, I am removing a 1990 40 Mariner (AKA Classic 50). Will the thru hull transom holes be the same?
Bigshot posted 06-18-2003 02:03 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Not sure about holes but mount engine 1-1.5" ABOVE the transom.
skred posted 06-19-2003 08:20 AM ET (US)     Profile for skred  Send Email to skred     
Peter, my '85 15CC with 2001 Merc 50 4-C Carbureted runs high 30's with 245-lb. me and assorted gear aboard. Boat came with a 70 Yam 2s and WOT was scary: 45+....
If you can save a reasonable amount buying a 50, I'd go with it. If there's only a couple hundred difference then the 60. (IMO)
Peter posted 06-19-2003 04:17 PM ET (US)     Profile for Peter  Send Email to Peter     
Thanks Skred.

My primary interest in the Yamaha 60 versus Yamaha 50 is getting the larger displacement (51 versus 42 cubic inches). The extra displacement is worth the extra bucks in my opinion.

Given my limited experience with the Johnson 48 SPL, for most uses, I think that 50hp is probably enough for the 15' hull. My normal rule is to put the maximum rated power on a hull, but in the case of the classic 15' hull, I believe that the maximum would be more than too much for me.

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