Re-power or leave it alone?

[inthedirtagain]

Currently have a 1986 Merc 90 on my 16ft Larson All-American. It runs fine and pulls the family around the lake on skis, tubes, and boards without any problems. The boat is rated up to 120hp, and I'm thinking that I'd like to possibly do this next spring. Since my current setup is functioning fine (decent fuel mileage, 120psi x 6cyl), I'm wondering what the thoughts of others would be. Personally, I wouldn't mind being able to pick up a little more speed. Right now, I'm around 35mph at 4800 WOT. My manual states upper range of 5000rpm, so my performance is respectable. A re-power to a 115/120 and propped correctly should allow me to hit around 45mph, but I'm looking at spending around $1500 to do so. If it were your boat and your money, would you do it?

 

[jimmbo]

Re: Re-power or leave it alone?

Going to a 115/120 hp will give at best 5 maybe 6 mph. With a bit of tweaking, like raising the engine up a couple of holes on the transom bracket, getting rid ballast, like the wife and mother in law(girlfriends and mistresses can stay), and careful choice of propeller you should be able to get a few extra mph out of your present setup. A lot cheaper than a new engine. If you go with a used engine, make sure you're buying one that is prop rated as your 90 is prop rated.
I did the 90hp to 115 in 1984. I got a 10mph increase but my 90 was crank rated and the 115 was prop rated

 

[JimS123]

Re: Re-power or leave it alone?

Been there, done that. Never satisfied. Always got to go faster, but for what?

The old "slow" motor ran perfect and never gave a hiccup. Traded to a bigger one that looked like new and even paid $350 to have it "reconditioned" before I ever ran it. Broke down 2nd trip...took it back $100 more and it ran OK but broke down on vacation.

Dumped it and put the old one back on. Still not satisfied. Got another bigger one a few years later. Same expense and breakdown history.

Now the old one is back on again and I learned to be satisfied.

If you can afford a brand new motor, go for the bigger one. But if you're looking for a used bargain, keep the one you have!

 

[inthedirtagain]

Re: Re-power or leave it alone?

I thought about trying out different props, but the one that is on there doesn't have an indication of pitch. Any replacement I get could potentially be the exact same prop. Also, it doesn't appear that I can raise the height of the motor on the transom at all. It isn't bolted to a mount of any kind, just directly through the transom. I already have ventilation problems when turning hard, and my whale tail does nothing to prevent it (although I plane at 9mph). Cav Plate is a hair above the bottom of the keel, so I know its not sitting too low.

To be honest with you, my other boat had an Evinrude on it, and for some reason, I just feel more comfortable with those outboards. Don't know why because I grew up with Merc Towers on both my mom's boat and my grandfather's. Just wish I could get a little more out of this one without sacrificing my holeshot and losing my ability to pull the fam around.

 

[jimmbo]

Re: Re-power or leave it alone?

You say your motor is a 1986. In 1984 mercury started using the transom bracket that used the OMC bolt pattern, and like OMC allows for a 2 inch vertical movement in mounting height via 4 or five bolt holes

 

[inthedirtagain]

Re: Re-power or leave it alone?

We're taking it out tomorrow, so I'll post some pics of the setup.