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tjwierz2

comparison between older 60HP and new 50HP questions

2 posts in this topic

I have a 17'6" Crestliner with a '90 or '91 60HP Johnson. I am thinking about buying a new Merc or Yamaha, and I am curious if I would get the same performance from a new 50HP motor.

Will there be much difference between and older 60HP and a new 50HP. Should I stick with the same HP on the new motor? Thanks for the help.

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good question, first of all, all outboards after 1990 are rated propshaft horsepower, so a 50 horse regardless of 2 or 4 stroke, or manufacturer is supposed to be the same ponies. What can be different is the final drive rpm and the amount of torque the motor produces at the propshaft. this gets very tricky.

Before 1990 manufacturers could measure horsepower at the propshaft or the crankshaft. The prop is a true reading, some manufacturers would rate propshaft so you could put the largest possible motor on a given boat and claimed thier motors were faster and more powerfull. Other manufacturers would rate thiers at the crankshaft, so they would claim you get more horses for your money and their motors had a better power to weight ratio and claim the competitions motors were too expensive and heavy. I have seen private lab expieriments where the crank could measure 22 Horses powerhead alone, attach lower unit and at the crankshaft it was now 18horses (what the motor was rated at) but at the propshaft it was only 14 horses. The next manufacturer was 24 horses at the crank but 19 horses at the prop (which it was rated 18HP) So which one will be faster? of course the higher prop horsepower. In the late 1980s a great debate over the USCG hp ratings resulted in that all outboard manufacturers must rate thier motors at the prop to ba fair and safe.

Its like in the 1960's when all the sudden a car that had a 330 horse v-8 all the sudden next year they said it was a 260 horse model, same displacement engine, same tranny and same car, even the same carbueretor. The NTSA said all automobiles must be rated at the drive whhels and not at the engines crankshaft.

Also there is motor weight to consider, a 60 horse 2 stroke 60 weighs about 200 pounds where a 4 stroke 50 might weigh upto 300 pounds (depending by manufacturer) so your overall power to weight ratio is affected.

To make it short, stick with a 60, if the motor is propped correctly and planes good. If you goto a 50 you take an 16.7 percent loss in the prop hp that you may be dissatisfied with. If you were comparing a 160 to a 150 i would say dont worry about it because it would only be a 6% loss in horsepower.

Good Luck I hope this helps.

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The Warrior is back, and he's packin a new grill.

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