motor capacity

[RL]

I have an OLD Sears 12' aluminum jon boat that has a tag rating it for 7 1/2 hp , and I have a much newer 9.9 Johnson ( '78 ) that I use for a kicker on my larger boat.<br />What kind of modifications would I need to do to hang that 9.9 on the thing ( I'm not planning on racing the thing, this is just for solo fishing)?<br />Or considering the age of the boat, would the weight/stress of a 7 1/2 at the time be comparable to a more recent 9.9 ?<br /><br />Thanks-------Robert

 

[JB]

Re: motor capacity

Moving to General Outboard.

 

[cobra 3.0]

Re: motor capacity

I doubt that the difference in power would cause you much trouble. My buddy had a similar kind of set up and all was fine. He had a regular v shaped front tinny. Maybe put a little weight in the front if you plan to do it alone...a sack of sand would do. Go slow and ease it up. Wear your life jacket on any small boat...especially if you "go it alone".

 

[rickdb1boat]

Re: motor capacity

I agree with Cobra. The weight difference should be negligible, depending on the year of the old one and new one. Give it a try and see how it goes..

 

[RL]

Re: motor capacity

That's kind of what I figured.<br />I was planning on setting the fuel tank up in the middle, and of course, I can't forget the cooler full of fish ( that I'll most likely have to pick up at the market , the way my luck's been running <br /><br />I'm with you on the life jacket,I don't swim like I used to, but it's almost a bit redundant on the lake I'll be going out on. If the boat sinks, you can pretty much walk back, and if it gets too deep, you can hop from stump to stump<br /><br />------Robert

 

[BF]

Re: motor capacity

not that it fits your Q perfectly, but I'll tell you my story... I have a couple of old cheapo 12' cartopper tinnies that live at the cottage. I think they're rated for 7.5 hp. A couple seasons ago I got a new to me 15 hp evinrude ('82). I needed a couple days worth of wrenchin' to get it running, and after I was done (at the lake) I wanted to test run it, but didn't have a more suitable boat. I thought, what the heck, I'll put it on a little one and take it easy... just to get an idea of how it runs you know. Lake was like glass, no one else around (except wifey on the dock shaking head). My motor ran great at low speed, and I couldn't help but see what it could do. There isn't a bad ending to this story, but I'll say that little tinnie has only gone faster on the roof of a car. I must've been doing 30+ mph. (felt like 90)... When I realized that the whole bottom of the boat was dishing upwards at warp speed I realized I was having too much fun and called it a day. The 6 hp that we normally use on those little guys is about the right size.<br /><br />So, 15 hp (but same motor as yours) was way too much, you might be fine with a 9.9, but be careful and listen to what the old girl tells you (old aluminum might not wanna flex too much before it cracks).<br /><br />Brent

 

[RL]

Re: motor capacity

I don't think there's any danger of me trying any takeoff and landing drills with that thing. I don't much like going over walking speed in anything that small, too squirilly.

 

[steelespike]

Re: motor capacity

I know you will be careful but keep in mind you<br />will be 30% over the rating. and that is weight and power.Also keep in mind if anyone gets hurt<br />you might be in big trouble.

 

[Chris1956]

Re: motor capacity

RL I had a 12 Jon boat with a 7.5 HP gamefisher on it years ago. It would not plane well with just me in the boat, it needed another person (or weight)in the middle to hold the front down. I should have gotten an extended twist grip for it, and sat in the middle seat. Also, if I motored into the wind, the air would get under the front. I was always afraid it would flip over backwards, like the racing catamarans sometimes do in a crash.<br /><br />The bottom line is accelerate slowly and watch for the boat becoming unstable.