Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp

dannemand

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Hi?, i have an Evinrude 1984 6 Hp that is Belgium Derated to the 6 Hp, that is originaly 8 Hp, does anyone know how to fix it back to the 8 Hp, ore otherwise tune it up a bit.

Thanx, Brian.
 

Tim Frank

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Re: Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp

There are two schools of thought that you'll find in here.
I'm from the "By the time you make the changes (and add the parts), with the time and cost involved, if you want an 8 HP, you'd be better to sell the 6 HP and buy an 8HP school " :)
 

dannemand

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Re: Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp

@ Tim Frank, thanks for your advise, i am from the other school, the " do it your selve or you are a ****ING *****... :D just joke?n Tim, its not an option for me, i?m keeping it 6 ore 8 Hp...
 

Tim Frank

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Re: Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp

@ Tim Frank, thanks for your advise, i am from the other school, the " do it your selve or you are a ****ING *****... :D just joke?n Tim, its not an option for me, i?m keeping it 6 ore 8 Hp...

Do a few searches in here....especially on the " how do I make an OMC 9.9 HP into a 15 HP." threads ....note the original poster's name....check the responses....then fast forward a few weeks and see the OP's questions on why his now "13.9HP" runs like crap. :)

If you are really set on trying it, do a part by part comparison of carbs and intake/exhaust systems and make a list of what you need to change and price it out.
 
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slate1234

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Re: Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp

I have done a lot of searches on the internet regarding this as I have a 1983 6hp made in Belgium, I tried re jeting the carb and it ran like sh.t all I found was a damaged emulsifying tube, I put the old jets back in and it runs nice, I am waiting for my carb kit to arrive, now there is a restrictor plate on the inlet manufold that you could try fileing away at (I haven't the balls to screw up a good engine) I also have a 7.5hp carb and compairing it to the 6hp carb the throat on the 7.5hp is a lot bigger, which leaves me to belive at best they are a restricted 7.5hp but I made my mind up last week and I'm picking an 8hp up on saturday can't wait to try it on the sib, but please post your results
 

Tim Frank

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Re: Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp

I have done a lot of searches on the internet regarding this as I have a 1983 6hp made in Belgium, I tried re jeting the carb and it ran like sh.t all I found was a damaged emulsifying tube, I put the old jets back in and it runs nice, I am waiting for my carb kit to arrive, now there is a restrictor plate on the inlet manufold that you could try fileing away at (I haven't the balls to screw up a good engine) I also have a 7.5hp carb and compairing it to the 6hp carb the throat on the 7.5hp is a lot bigger, which leaves me to belive at best they are a restricted 7.5hp but I made my mind up last week and I'm picking an 8hp up on saturday can't wait to try it on the sib, but please post your results

Great post from the school of "been there tried that".
Hope the OP reads this.
Heck, if it was easy, everybody would be doing it. :)
 

dannemand

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Re: Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp

Great post from the school of "been there tried that".
Hope the OP reads this.
Heck, if it was easy, everybody would be doing it. :)

Hmmm... i had the feeling that there was some kind of fuel indlet reducer ore something fairly easy removeable.....seems not to be the case....
think ill be better of making my boat 100 kg. lighter ;-)
 

raczekp1

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Re: Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp

i had in my hands 6 hp and 8 hp model
you need:
1.carb mounting base(intake panel)
this base has bigger hole to suck more fuel+air mixture

2 carb from 8 hp, but not sure. i didnt measure carb throath. for sure i can say some years 8 hp carb is almost the same as 9.9 have
 

Chinewalker

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Re: Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp

Crankcase is different too, to accommodate the intake.
 

Tim Frank

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Re: Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp

Crankcase is different too, to accommodate the intake.

I was not trying to be negative; but I've seen a bunch of these posts in here for lots of different combinations....and have not seen one hat had happy outcome.
There is enough commonality for some of these "families" that it may be possible, but there are wayyyyyy more parts that need to be changed than is obvious. The $$$$ usually adds up quickly.
 

jimmbo

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Re: Evinrude 1984 6 Hp Belgium Derated, how to underate back to 8 Hp

It appears that a lot of people look at the specs for an engine, when they see another engine with the same displacement but rated at a higher Hp you can see the sparks and smoke coming out of their heads. They think that a jet change, or a 1/4 turn of some screw and they will suddendly get horsepower the manufacturer denied them. If only it were that simple. Sometimes it is only a larger carb. More often it is different porting in the block, along with exhaust tuning, different heads, reed and manifolds. To make more HP an engine has to turn higher rpms. The forementioned differences allow the engine to inhale/exhale better at higher rpms. The tradeoff is a torque curve moved to a higher rpm range, resulting in less torque and Hp at lower rpms. So taking 2 engines of the same displacement say 100 cu in, one rated 90 hp the other 140, the 90 will have much quicker accelleretion out of the hole than the 140 but once the 140 has reached higher rpm it has the advantage from the less restrictive breathing and will over take the 90.
 
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