how to determine what size engine to move uo to??

I just bought a 1968 Larson 17' fiberglass boat that has a Merc. 2 stroke 45hp. "50hp. Classic" outboard.

Nice motor, but way underpowered for this boat..

I wish to re-power with a 95 or newer Evenrude/Johnson 2 stroke but cannot find any information on what the max. HP. this hull will accept.

The difference in weight between a 90hp and a 115hp. even or Johnson is only seven pounds, but still 600 + for either
engine.

A less hp Evenrude or Johnson also weighs less, but I have been told buy a couple Even/John mechanics, that the 90hp. 115hp's are the most reliable in the 1995 newer 2 strokes....

Comments / opinions please..

Yes, I have checked the boat for a tag that gives the max. HP rating for the boat and have found none..

Thanks guys for any insight into what size max. HP or weight I can go..

stormmn

Re: how to determine what size engine to move uo to??

My old boat was similar to yours. Originally I had a 60 HP Rude, then upgraded to a 75 HP Johnson "Stinger". I found the performance to be excellent with both. If it were me I'd look for a J/E 3 cylinder 65-75.

Re: how to determine what size engine to move uo to??

I know 75hp is the max for a 1968 15' Larson. 90hp would sound about right for a 17 foot but i think you'd be pushing your luck with a 115hp. I'm sure the boat could "handle it" but for insurance purposes etc....

Re: how to determine what size engine to move uo to??

None of the 90/115HP engines weigh 600#. They are about 1/2 of that. I would recommend an inline 3 engine, as they are pretty light and powerful. A V4 motor is a bit heavier.

Re: how to determine what size engine to move uo to??

I know that in my state the fish and boat commision has a form to figure out the maximum recommended HP for a hull. Your boat registration commission probably will too. It takes into account the steering type, length, width at the widest point, transom width, transom height, and hull depth. In my stste it does tend to be a bit conservative so if the Coast Guard has similar tables, use them. At 17 feet long and with a 20 inch transom height, your hull should fall into about the 120 HP range.

If you decide to go with an OMC V-4, try to stay away from the 60 degree loopers. The older crossflow engine design tends to be a bit more reliable

AND----Too much horsepower is never enough! Hang a 250 on it LOL

Re: how to determine what size engine to move uo to??

Frank Acampora said:

I know that in my state the fish and boat commision has a form to figure out the maximum recommended HP for a hull. Your boat registration commission probably will too. It takes into account the steering type, length, width at the widest point, transom width, transom height, and hull depth. In my stste it does tend to be a bit conservative so if the Coast Guard has similar tables, use them.

Click to expand...

Just a quick note for anyone in Pennsylvania that may want to have the PFBC do the figuring for you.

Starting in 2013 the Commission will no longer be issuing capacity plates or doing the calculations. PA was the only state still doing that and since their formulas were not the same as USCG they were required to discontinue that service.

This has changed some other regulations too and boats can now be legally registered without a capacity plate.

Re: how to determine what size engine to move uo to??

Larson Boats

Here is a link for Larson boats. It goes back to 1969. Show a few boats the are just under 17', all seem to be rated at 120hp.

Knowing your model will help get the max hp your looking for.

Re: how to determine what size engine to move uo to??

correction to my statement, the 90hp and 115 hp's weight is just over 300lbs. not 600lbs as I stated... Brain fart, sorry!

stormmn

Re: how to determine what size engine to move uo to??

This may help.