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  50 hp classic on a 15 classic

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Author Topic:   50 hp classic on a 15 classic
Scanner Boat posted 10-21-2003 08:18 PM ET (US)   Profile for Scanner Boat   Send Email to Scanner Boat  
much to my dismay I could not get the 70 yamaha to replace the extreemly tired(read blown) 50 on my 1981 classic 15. However I did find a 1981 50hp merc that has about 20 hours on it and looks like it just came out of the box I could not beleive it! I may just have to get this motor for the nostalgic reasons even though it has no power trim. What do you think? Thanks, Chris
jimh posted 10-21-2003 09:18 PM ET (US)     Profile for jimh  Send Email to jimh     
For a reproduction of the original Boston Whaler performance chart on the 15-foot hull see:

For comments from an experienced user with a 50-HP engine, see:

For a chart showing performance of a 15-foot Boston Whaler with a 50-HP engine, see:

Bigshot posted 10-22-2003 11:17 AM ET (US)     Profile for Bigshot  Send Email to Bigshot     
For $400 you can get a CMC power tilt bracket.
Florida15 posted 10-22-2003 06:41 PM ET (US)     Profile for Florida15  Send Email to Florida15     
I've got a 1981 Johnson 50 on my 1987 15' Striper. It will run at 34 mph. I have a CMC tilt on it. The tilt works fine but it came with the boat. I don't know that I would spend $439 (Cabela's) on one. I have thought about getting a new or newer motor and if I do, I will replace it with another 50. I think it's just right for the 15' and not as heavy as the 60 or 70.
4whaler posted 10-22-2003 06:48 PM ET (US)     Profile for 4whaler  Send Email to 4whaler     
Thats what I had on my first 15 foot classic. It was the perfect motor for the hull and it had no T/T. I just had to remember to not have the motor in reverse when I wanted to pull it up as the lock hooks were engaged to keep it from climbing out of the water on its own under reverse thrust. Draft is so shallow that I never had a problem with no T/T once I got the trim pin set to the right hole (2nd up from bottom if I remember right)
Sammy posted 10-23-2003 10:46 AM ET (US)     Profile for Sammy  Send Email to Sammy     
I have a '79 15' Sport that was bought as a project. It had spent 16-17 years slipped in salt. The next 6-7 years it sat unused in a garage.

It came with a 55hp Evinrude that was toast - heavily corroded, very poor compression, push rods rattled when flywheel rotated, and on and on.

I was looking for a good used later model 70hp - preferably Mercury, but I would have settled for a Yamaha :).

What I found - and couldn't resist - was a motor almost identical to what you are considering. It was an immaculate 1982 Merc 50hp in-line four cyl. that came off an older (he's approaching 90 years old) gentleman's fishing boat from a lake in northern Minnesota. Receipts for all maintenence since new. Amazing.

A number of folks on this site including Clark Roberts and jimh have commented favorably on this hull/power match. Others I know that have owned the 50 hp in-line four spoke highly of it, and I went with it.

A leakdown test showed an identical 4% on all cylinders so the power head is strong. Mounted on a CMC Tilt Trim unit with 6.5" of setback and 2" of lift, GPS reads 36.2 mph with one person (200 lbs.) and 4 gallons of fuel. It came with a 14 pitch aluminum prop that's not bad but could use a rebuild. There's no tach - it will be added over the winter with the new mahogany. But as jimh pointed out, there's plenty of good information on this hull/power combination in the refeence section - and my numbers are very close to those in reference.

That's with a very slippery hull - five coats of bottom paint stripped off, lots of dings and dock rash faired out and a very tired gelcoat reshot with a quality acrylic uerathane that was wet-sanded with 1500 and buffed to a high gloss.

I'm really impressed with this motor. It's incredibly smooth runing at speed and at idle. Easily holds the hull on plane at 18 mph. Very quiet for a two stroke. And idles down for a excellent trolling speed. I'm still working on determining range with two 6 gallon fuel tanks - but it doesn't seem be be very thirsty.

I'm still curious about how a 70 hp will push this hull. Even if I eventually go to a 70 hp, the classic 50 will be used for something else - it won't be sold.

I know the hull originally came with OMC power, but that vintage Merc looks great on the vintage Whaler.

Scanner Boat posted 10-23-2003 05:50 PM ET (US)     Profile for Scanner Boat  Send Email to Scanner Boat     
I bought the pristine 50 and mounted it. If it will run even marginally better than the old 50 I will be happy and probably add the trim next spring. I always felt that the old 50 used fuel like a jet fighter and polluted like the valdez on steroids but it did run very smoothly and still made 5300 rpms with the 14"pitch untill a few months ago. The dealer is going to put in carb kits and dyno run the engine to verify performance before the launch next week. Aside from a few minor nicks on the skeg it looks like this motor has not spent a night out of the garage ever. I cannot wait.... Scanner Boat
scaleplane posted 10-24-2003 12:37 PM ET (US)     Profile for scaleplane  Send Email to scaleplane     

If it runs well, you're in business.

When I bought my '76 15' Sport, it had a same-era 50 HP Mercury 500 on it. Four cylinder, big and very smooth running - when it ran. Mine was pretty worn out. I had the wiring harnesses replaced due to hardened insulation, and had it worked on several time for plugged up carburetors. It didn't have tilt/trim, so my left arm was getting pretty sore from lifting it up when I tied up for the day. It was nickel and diming me to death.

I finally gave up on it and bought a new Johnson 40 HP. The Johnson isn't quite as smooth as the old Merc, having only two cylinders. It also doesn't have quite the power of the old Merc, although it still gets out of the hole nicely and hits over 30 mph WOT. But it is quieter, has one other advantage - the Johnson is MUCH better on gas. That Merc sucked it up pretty fast.

I do miss the classic looks of that old Merc on my Whaler!

Bigshot posted 10-24-2003 02:25 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
I had a 1981 Merc 50 on my 15' Glastron. What a nice engine, too bad the owner never greased the driveshaft and it welded itself into the crank. Damn thing ran like a sewing machine. They look so cool from the front, especially on a 13 or 15' Whaler. I just threw out a mint 78 50 shroud that nobody her or on E-Bay wanted, you could have had a spare:)
Scanner Boat posted 10-25-2003 10:09 PM ET (US)     Profile for Scanner Boat  Send Email to Scanner Boat     
Thanks Bigshot however I have a complete spare (less 1 piston) if the powerhead lives I will be set for another 20 years

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