1986 6hp upgrade to 8hp with new carb?

[el_duderino]

I was hoping to find out if there is any way to get more HP out of my 1986 6hp. I have heard that I can put a 8hp carb on it, like putting a 15hp carb on a 9.9hp outboard. <br /><br />If anyone has done this can you tell me how I would start to go about this. Where I can look for a carb that will fit. Can I put new jets on the carb with the same effect. <br /><br />The engine is just to small, and was hoping to put some more power back into it. Thanks for the help.<br /><br />The Dude

 

[JB]

Re: 1986 6hp upgrade to 8hp with new carb?

I recommend that you go find a good 9.9hp engine and trade, Dude. <br /><br />The 9.9 has more displacement and you would notice the increased torque. <br /><br />Even if you modified your 6 to exact specs for an 8 the only real difference would be on top end, and you might not notice that without a speedo.<br /><br />My guess is that you can trade for less bux than you can hop up the 6.<br /><br />Good luck.

 

[el_duderino]

Re: 1986 6hp upgrade to 8hp with new carb?

Yeah I thought about that but the added weight to a 9.9 would be a disadvantage. This motor is currently on a 12 Tracker. The Max HP on this thing is 6 hp, and I am just looking for a little more top end. The torque is fine the way it is. What I really need is a 13 Whaler.

 

[Chinewalker]

Re: 1986 6hp upgrade to 8hp with new carb?

Hey Dude,<br /> There is no easy way to upgrade a 1980s 6hp to an 8hp. The 8hp used a larger intake manifold with one extra reed per cylinder, in addition to a slightly larger carb. The larger intake manifold has a different bolt-pattern and the crankcase is a different casting to accomodate that. <br /> Your '86 6hp is essentially the same as the early 1980s 7.5hp of the same configuration. OMC upgraded the power the same year that the industry re-rated all their motors at the prop, meaning the 7.5 was no longer a 7.5. So, they dropped it to a 6hp and beefed it up for a new 8hp model...<br />- Scott

 

[el_duderino]

Re: 1986 6hp upgrade to 8hp with new carb?

Thanks Chinewalker. <br />Any idea if there are aftermarket jets for the carb I can add to give a little free HP. <br /><br />The Prop is about 65%. Any idea if a new prop would increase top end noticeably? Are there props designed for small motors that increase top end? <br /><br />I have a feeling the answer would be no since the prop doesn't make enough rpm to be ineffecient.<br /><br />Basically I am looking for anything that will get this thing moving faster for less than $200 TOTAL. The boat is limited to 6hp, but it seems like it could do A LOT more.<br /><br />Thanks for the help everyone,<br /><br />The Dude

 

[Solittle]

Re: 1986 6hp upgrade to 8hp with new carb?

Dude I think the only thing you can do is to make sure you are getting the best you can from what you've got. Basically that would be tune & prop. For the prop you need to know thw max rated rpm for the motor and the max you are now turning. There is a mini tachometer that I think is called Tiny Tach that you can get to measure what your motor is putting out now. Once you know that you go up or down on prop pitch.

 

[Chinewalker]

Re: 1986 6hp upgrade to 8hp with new carb?

Dude,<br /> The only thing changing jets is going to do is make the motor run rich or lean. You can't simply add more fuel without making it possible for the motor to receive more air (restricted by the smaller reed plate).<br /><br /> As SoLittle noted, the best thing you can do is make sure you're getting all 6 ponies as it is. Make sure the carb and throttle linkage is giving you full advance. Make sure the propeller is in good shape - you said it was "65%". I'm not sure what that means - 65% still there? 65% missing? You want your propeller to be as good as can be and to be thr right one for whatever application it's used for. Using too large a prop is like driving around in 5th gear all the time, while using too little prop is like driving around in 1st gear. New props in several sizes are available from your local Johnrude dealer, as well as afermarket sources like Michigan Wheel.<br /><br />- Scott

 

[BillP]

Re: 1986 6hp upgrade to 8hp with new carb?

I need a 6...sell yours to me and find an 8hp.

 

[el_duderino]

Re: 1986 6hp upgrade to 8hp with new carb?

hehe, no way in hell I'm lettin go off these peach BillP. My Poppi used this thing to kill 1000 birds a season for many many years. Then it sat in Poppi and Mimis garage for awhile when Poppi left us. Once Mimi realized I wasn't going to pawn it, she let me have it. I didn't have an opportunity to use it for around 5 years. I lugged it around with me from TX to NM and back to Houston, then back to Dallas again to Austin afterwards to Fort Lauderdale, and now finally in Wilton Manors FL. And just this March04 I bought the POS this diamond sits on. Since then I have put about 100 hours on it, and still counting. When I think about it, and especially when I take the hatch off, I can smell that old garage. I can also see my Mimi looking at me thru the big glass window in the kitchen while messing around with it, pulling the crank, and day dreaming about using it someday. So as you can see, unfortunatly for you, I can't sell it. To many memories there. I hope to have this thing well into to 2094. <br /><br />Again thanks for all the help. I will check the linkage to the carb tommorrow. I guess to do this I will leave it in neautal, use the throttle grip and get it going full max. Then push the carb throttle lever max and listen for a difference in RPM. Hope it works. Any better ideas with out having to bye a carb syncronizer capacitor modulated timing device.<br /><br />Happy Holidays,<br />Dude

 

[steelespike]

Re: 1986 6hp upgrade to 8hp with new carb?

Believe it or not you probably can get more speed with a little bigger boat.If you find the <br />biggest 12 you can, nice and wide and a good full 12 ft.it will get up on the water easier.When running alone if you get or make an extension handle sit in the middle seat and she should get up and plane.If you run sheltered waters a nice wide flat bottom like a Jon boat will really get up a scoot.Maybe 15 or 18 mph if your not too heavy.We used to have a flat bottomed 12 ft steel boat with a 5hp. that planed with a 120lb. adult and 2 small kids total load about 200 lbs.With the adult and an extension handle it popped on plane almost instantly.

 

[steelespike]

Re: 1986 6hp upgrade to 8hp with new carb?

Forgot to mention be sure your motor anti ventilation plate (Just above the prop) is about even with the bottom of the boat.Get the trim angle right first.Prop shaft should be approximately parralel with the bottom of the boat.Once it seems to run best then raise the motor virtically 1/4 inch at a time till just before ventilation becomes a problem.Simply add a 1/4 inch stick on the top of the transom for each step up.The idea is to have as little in the water as possible.

 

[Mark42]

Re: 1986 6hp upgrade to 8hp with new carb?

There is no question about it. You need to slap a supercharger on that puppy. Bingo! Instant 18 hp.<br /><br />