vintage outboard hp ratings/weight compared to modern

[silveraire]

I am in restoring a 1968 silverline belaire. I am about ready to repower and have a few questions. It has a max h.p. rating of 120hp. How do the h.p. rating back then and now compare. Also, how do they compare with the weights. For example, does a 100hp from 1968 weigh more or less than a modern 100hp 2 stroke. I was thinking about a 115 yamaha four stroke, how much heavier are the four strokes. I don't want to overload the transome.

Any recomendations on power for this boat, it is 16' and weighs around 1000lbs.

 

[JB]

Re: vintage outboard hp ratings/weight compared to modern

Howdy, silver.

Before the 80s outboard power was rated at the powerhead. During the 80s the ratings were changed to the prop. The difference is the power used up by the drive train and gearcase, typically around 5%, so a modern 115 is about as powerful as a pre-80s 120.

To compare weights you must get make and model specific. There is typically about 100lb difference between modern carbed 115 2 strokes (around 310#)and modern 115 EFI 4 strokes (around 420#). DFI 2 strokes fall between.

Your boat sounds like it would be happy with anything from 90 to 115hp. I see no reason that a 115 EFI 4 stroke would be too heavy as long as you distribute the weight of the rigging and load forward of where it would be for a 2 stroke 90.

Good luck.

 

[tashasdaddy]

Re: vintage outboard hp ratings/weight compared to modern

whats you transom depth. and does it have a splash well?

 

[silveraire]

Re: vintage outboard hp ratings/weight compared to modern

It has a 20 inch transom and a splashwell. thanks for your replies so far.

 

[JasonJ]

Re: vintage outboard hp ratings/weight compared to modern

You can do what you propose. A modern 4 stroke 115 will weigh roughly 100-150 pounds more than a 60's era 2 stroke. You might want to move the fuel tank and battery forward to help compensate. On my boat, I have a 9.5 horse kicker, my 69 Merc 1250, and my 20 gallon fuel tank all at the back, and it is fine. I did move the battery forward, but just so it could be next to the other battery for my trolling motor.