12' alum boat. can i put 5 more horse power on it

[snowmobilefanatic]

im buying a 12 foot alum starcraft boat from the 60's. the max horse power on it is 10 and i want to put a 76 15 horse johnson and i was wondering since the 10's from the 60's probally weigh just as much as the 15's in the late 70's. the max load on it is 500lbs. and how much more weight is the 15 than the 10, it cant be that much becuase the only difference is the size of the cylinders and pistons.

 

[CATransplant]

Re: 12' alum boat. can i put 5 more horse power on it

The weight won't be a factor. Depending on your boat's design, the additional horsepower might be a factor, though. <br /><br />Around here, I see a lot of 15hp OMC motors on small aluminum boats. All of them seem to have a 9.9 hood or cowling on them though. I think that could be so they don't get busted on the under 10 hp lakes. Ya think?<br /><br />Myself...I wouldn't worry too much about putting a 70's model OMC 15hp on that boat. If it's too fast, then don't run it WOT. A guy's gotta use what a guy's gotta use.<br /><br />I do notice that the 15hp motors are cheaper than the 9.9s around here. Lots of small lakes with an under-10 hp. limit.

 

[Chief101]

Re: 12' alum boat. can i put 5 more horse power on it

I think a 15 is the perfect powerplant for a 12' tinnie. Mine had a 20 which was a little dangerous, than to a 10 which was almost enough, and now a 15 which is just right. Chief Chief

 

[WillyBWright]

Re: 12' alum boat. can i put 5 more horse power on it

In most states, you'd be breaking the law. Weight isn't the issue. Horsepower is. Otherwise you'd have max motor weight stated instead of max Hp. Force made a really light 25Hp about the same weight as the old 50's 10Hp, probably lighter. Would you put that on there??? <br /><br />The weight issue is really brought up alot by Merc owners. An inline-6 90Hp weighs the same as 150s. So why not put a 150 on a 90Hp boat? Yikes!!! <br /><br />People were dying from overpowering their boats. So the law devised a formula and weight has nothing to do with it. It's determined by boat dimenstions. You might plug your dimensions into that formula and see what you get. You may be able to get the boat re-evaluated. <br /><br /> Really Excellect Information Here

 

[snowmobilefanatic]

Re: 12' alum boat. can i put 5 more horse power on it

haha im doing the same thing with the 9.9 hood, i have a evinrude hood from 74 and the emblem that says 15 was lost a long time ago and all it says is evinrude, but i live on a lake that you can use more than 10 so it isnt a problem. i thought weight whould be a problem because its alot more stress on the transom. ive seen other 12 boats with a 15 hp limit on it, whats different with them? just more alum and ribs and beefier transom. i know a guy who beefed up his 14 alum boat and put a 25 on it and that was FAST. a little too fast for by your self

 

[WillyBWright]

Re: 12' alum boat. can i put 5 more horse power on it

Lets see... 12' boat with two adults and a dog, planing on a max 10Hp lake. No 9.9 is gonna do that and Wardens know it. Might as well wear antlers during deer hunting season.

 

[cobra 3.0]

Re: 12' alum boat. can i put 5 more horse power on it

I put my 15 Evinrude on my 12 ft fiberglass boat. It's fast, but not dangerous. You do need to slow down on windy, wavy days but that's like anything you drive, weather often dictates how fast you can go.

 

[snowmobilefanatic]

Re: 12' alum boat. can i put 5 more horse power on it

weather around here isnt too bad. the lake is skinny and long and surrounded by tall trees and it almost always flats out calm like glass around 6 in the evening. when i pick up the boat later on today ill give the details on the design and see if it will hurt it or not.<br /><br />thanks for eveyones help! once again this site is the best!

 

[CATransplant]

Re: 12' alum boat. can i put 5 more horse power on it

"Lets see... 12' boat with two adults and a dog, planing on a max 10Hp lake. No 9.9 is gonna do that and Wardens know it. Might as well wear antlers during deer hunting season."<br /><br />Well, if you're that stupid, you need a ticket, then. Seriously, though, around here you can buy 15 hp OMC engines a lot cheaper than 9.9s. I don't have one...heck, my 12' tinnie has a 5hp on the back, but I've looked, since my boat is rated for 10 hp. I'd love to have a 9.9, but they cost more than the 15s. I'd be tempted to buy a 15 and slap a 9.9 hood on it, then just take it easy. I'm not in that much of a hurry, but it would be nice to plane a little on the larger lakes I fish.

 

[deejaycee_2000]

Re: 12' alum boat. can i put 5 more horse power on it

So .... if you're not breaking the law in your state .. then go for it ... In South Africa everything goes ... here is nothing like breaking the law ... the law here breaks itself ...

 

[CN Spots]

Re: 12' alum boat. can i put 5 more horse power on it

$500 fine in AR for exceeding hp limit on restricted lakes. Get caught with a 9.9 hood on a 15... twice that. ouch. Better off painting over your 15's hood or removing all the decals (not just the hp) and fessing up ONLY when they bust ya. But as was stated before, if there's no law where you are, I wouldn't worry about it.<br /><br /><br />spots

 

[Gfriedman]

Re: 12' alum boat. can i put 5 more horse power on it

CN Spots, how did you get busted twice for it? if it says 9.9 how did they know it was a fake hood?

 

[Paul Moir]

Re: 12' alum boat. can i put 5 more horse power on it

Rather than getting a 9.9hp hood, why not just get a 9.9hp carb for it? I'll bet you can get it on ebay really cheap as so many people put 15hp carbs on. And that's the only difference in '76.<br /><br />You could always swap back, the change out would only take 15 minutes.

 

[BF]

Re: 12' alum boat. can i put 5 more horse power on it

I've run my 15 'rude on my dad's 12' aluminum rated for 10... I found it a bit on the fast/wild side at WOT when there's not much weight in the boat. So, I'd say it was a bit too much of a good thing. Yes, you could throttle back.<br /><br />BTW, I had a 9.9 on a 12' for long time. No problem planing with 2 adults on board.