tuned down 25hp 1979 Evinrude

[mistermann]

I just got a 1979 25hp evinrude. The motor runs ok on slow speed, but has some kind of limitation so it only gives about 5hp. I think someone tuned it down to prevent the previous owner from damaging himself as he was old and drinking a lot Can anyone tell me what i might do to tune it back up?
Cheers. -M

 

[tashasdaddy]

Re: tuned down 25hp 1979 Evinrude

could very well be dirty carbs.

 

[mistermann]

Re: tuned down 25hp 1979 Evinrude

The guy I got it from said someone had tuned it down for him so it would not use so much gas , so I think someone definitivley has done something to it.

I'm thinking of getting a carb kit and cleaning it up, cause it's a bit old and dirty. Just wondering if that will do the trick or if there is some other parts I might have to change aswell. And if there are some other parts that I can change and it runs fine, then should I open up the carb and put in a new kit anyways? - if it's working don't mess with it right?

I have a spare parts engine aswell, so I can take some parts from that. Any tips on what parts may be changed or where the limitation may be located?

 

[mistermann]

Re: tuned down 25hp 1979 Evinrude

Well I've taken appart the carb from the spareparts engine, cleaned it up and mounted it on the engine. I've also cleaned up the fuel pump and checked that the plugs got spark. (The plugs are a bit old, but seem to be working. Is there any reason for changing them?) Also changed gear oil. Everything looks pretty neat. I'll do a test run tomorrow and let you guys know how it turns out.
- m

 

[freddyray21]

Re: tuned down 25hp 1979 Evinrude

Well I've taken appart the carb from the spareparts engine, cleaned it up and mounted it on the engine. I've also cleaned up the fuel pump and checked that the plugs got spark. (The plugs are a bit old, but seem to be working. Is there any reason for changing them?) Also changed gear oil. Everything looks pretty neat. I'll do a test run tomorrow and let you guys know how it turns out.
- m

if they look old or you think they are old replace them. They can fire great until under a load then break down. For about 2 bucks a piece or less why cheap out?

 

[mistermann]

Re: tuned down 25hp 1979 Evinrude

Hi.
Well I got the new spark plugs, but as I screwed them in i guess I used a bit to much torque (I did not use that much. Perhaps someone already did some damage there.) Anyways the threads in the top were destroyed, so now I'm replacing the top with the one from the spareparts engine. I'll also do a test to see if the fuel pump delivers as much as it should by taking the fuelhoze of the carb and into a bottle to check the squirt.
Laters...

 

[samo_ott]

Re: tuned down 25hp 1979 Evinrude

After you put the new head on with a new gasket I would do a compression test to ensure you have a good baseline and know the condition of the engine.

Also if you don't know the torques of the plugs or head bolts get a torque wrench and manual and tighten em up right you'll have more problems.

 

[jbjennings]

Re: tuned down 25hp 1979 Evinrude

The guy I got it from said someone had tuned it down for him so it would not use so much gas , so I think someone definitivley has done something to it.

I'm thinking of getting a carb kit and cleaning it up, cause it's a bit old and dirty. Just wondering if that will do the trick or if there is some other parts I might have to change aswell. And if there are some other parts that I can change and it runs fine, then should I open up the carb and put in a new kit anyways? - if it's working don't mess with it right?

I have a spare parts engine aswell, so I can take some parts from that. Any tips on what parts may be changed or where the limitation may be located?

Something sounds strange about "tuning it down" to me where it wouldn't use so much gas. the only thing I can think of would be something to limit the movement of the armature plate or perhaps on the throttle gear. I wouldn't think you can "detune" the motor. It's got to have the right spark advance and fuel/air mixture or it would ruin the motor. It's got to be some kind of stop screw to limit the movement of the throttle mechanism.
I'll be interested to hear your test results.
Good luck with it,
JBJ

 

[mistermann]

Re: tuned down 25hp 1979 Evinrude

Hi.
I've taken the top off. The gasket looks fine. Do I need to replace it? It's probably a week or two wait to get hold of a new one, and also prob a bit expensive. I'm in Norway, so everything is a bit more expensive here. Like the sparkplugs were $9 apiece. And that's stright from the supplier.
I'll get a torque wrench for the plugs.
I don't have the equipment to do the compression test, but I guess I can get the guys over at the maritime repairshop up the street to help me out on that. Just out of curiosity - how is the compression test performed?
Cheers.
- m

 

[wilde1j]

Re: tuned down 25hp 1979 Evinrude

New gasket needed any time head is removed.

You don't need a torque wrench for spark plugs... just don't overtighten. It IS needed for head bolts, however.

Compression measured with a pressure gauge. Not a very expensive item here ~ 15 to $20. Just remove the spark plugs and spin the engine over with gauge connected to each cylinder (one at a time, of course).

 

[mistermann]

Re: tuned down 25hp 1979 Evinrude

Hi guys.
I just realized that this is not a 79. It's probably a 76, at least it appears so according to the drawings of the cylinders and crankcase from the brp parts site. :redface: Guess this does not make a whole lot of difference when it comes to changing the top.
I'll get back as soon as I get it assembled and do a test.
Cheers.
- m