I have a 03 15hp 4 stroke Nissan and was wondering how hard it would be to convert it to a 18hp outboard. They are basically the same engines except the air intake on the carburetors are different. Has anyone ever done this, and would it be worth the trouble?

sounds like a headache to me.

matt

Tx. Fisher, I understand this is fairly common with Tohatsu/Nissan outboards. They will make 2 or 3 different power ratings from the same engine, and they use restrictors and jetting to achieve different power levels. Bass and Walleye Boats Magazine tested several engines in the 25-30 hp range a few years ago, and they commented that the Nissan/Tohatsu could gain several horsepower by removing the restrictor and installing the jets from the more powerful engine. Certainly not an impossible task. I bet it could be done in a couple of hours if you have a decent assortment of tools. Would you spend $10 and 2 or 3 hours of time to gain 20% more power from your engine? I would in a second. And I guarantee you will notice the difference. That's a pretty big gain, percentage wise.

Artie

you must be very bored!

It's more to it then that. Carburetor & Camshaft to start with. Definitely not worth the expense to obtain another 3hp.