1983 35 hp Evinrude

[WhopperPlopper]

Have a 1983 35hp Evinrude that starts and runs seemingly okay but is consistently 70 psi on both cylinders. Should this be higher and what can I do, if anything, to raise the psi and performance. Background: This motor is new to me and only started it in my garage and I personally have not taken it out but previous owner did say it ran tremendously... (maybe saying that for me to buy it)

 

[nccatfisher]

That is right at the borderline before it isn't going to start/run correct for you. It possibly could have some stuck rings. You could research some of the threads on here where Pappy has given some advise on bringing old motors back that have been setting and breaking rings loose/removing carbon then doing compression checks to see if that helped. Otherwise a rebuild may be in you future if you want to revive it.

 

[RaisedByWolves]

That is right at the borderline before it isn't going to start/run correct for you. It possibly could have some stuck rings. You could research some of the threads on here where Pappy has given some advise on bringing old motors back that have been setting and breaking rings loose/removing carbon then doing compression checks to see if that helped. Otherwise a rebuild may be in you future if you want to revive it.

This....BUT


Compression testers vary and even then if you dont know the proper way to use one results can be less than optimal.

I struggled with a motor last year that read 110/110 and was a bear to pull over. And while it started and ran it would act up bad after anywhere between 2min and 10min. Turned out to be a blown head gasket that was blown on both cylinders due to a less than stellar install.

 

[Weldorthemagnificent]

When you pull it over does it go easily or do you feel the compression? If you pull it slow, you should be able to feel it " bup bup bup ". My point is both your numbers are the same so I'm guessing the gauge is reading low. If one was reading 110 and the other one 85 I'd be looking closer at the motor. Automotive gauges don't always read accurately on small engines, especially piston port 2 strokes. I'd be plopping that motor on a boat and trying it out before anything else. Then if it works replace water pump, new champion plugs. Champion! No others! And run that dude. They are great motors. Mine pushes my 16' vhull perfectly.

 

[WhopperPlopper]

Thanks for everyone’s input! It’s actually an electric start, and has the shift cables on the left side (facing the stern) and throttle on the right. Came on a 83 stinger pro (see my rebuild thread) and if it runs wide open to my other 35hp ‘rude it will push that modified v perfect.. I am
Open to all ideas but will update everyone soon and would like to
See what happens under load

 

[wmk0002]

I guess theoretically you can take your air compressor and set the regulator to a specific pressure and shoot that into your compression gauge and see what it reads. May tell you how accurate the reading is on the tester? I have a Harbor Freight tester that wont climb over 60-70 psi in a couple of motors but my Innova gauge will read 110-120 psi in the same motors. However, Ive shot 90 psi air into the Harbor Freight tester and it read about 85 psi so that test I mentioned above may either not work at all or not on HF ones at least.

 

[WhopperPlopper]

Excellent idea wmk, that is a good starting point while I wait for a buddy to bring his over. Mine was a cheap one I got off amazon after losing long time favorite one.

 

[lckstckn2smknbrls]

I would sea foam the motor.

 

[CedarRiverScooter]

I would sea foam the motor.

+1

You could even put motor with spark plugs facing up & put some in spark plug holes & let it sit. Have pistons mid stroke. Maybe rings are gummed up.

 

[MrGiggles]

If it runs good, why worry?

The problem with testing engines of small displacement, the volume of the tester hose adds to the combustion chamber volume, lowering the compression ratio. Unless you have a tester with the Schrader valve in the tip at the very end of the hose, you'll get false low readings.

I generally don't put much faith in the actual numbers of a compression test, variation between cylinders is what matters the most.

 

[wmk0002]

If it runs good, why worry?

The problem with testing engines of small displacement, the volume of the tester hose adds to the combustion chamber volume, lowering the compression ratio. Unless you have a tester with the Schrader valve in the tip at the very end of the hose, you'll get false low readings.

I generally don't put much faith in the actual numbers of a compression test, variation between cylinders is what matters the most.

Interesting point, never considered that.

 

[RaisedByWolves]

If it runs good, why worry?

The problem with testing engines of small displacement, the volume of the tester hose adds to the combustion chamber volume, lowering the compression ratio. Unless you have a tester with the Schrader valve in the tip at the very end of the hose, you'll get false low readings.

I generally don't put much faith in the actual numbers of a compression test, variation between cylinders is what matters the most.

IF, it had stuck rings you might damage the piston/rings/cylinder.

Not that I think OPs motor has stuck rings, but I would put it through a few heat/cool cycles in a barrel, then check readings again if that were my concern.

There really should be a sticky covering compression testers and how varied readings can be.

 

[WhopperPlopper]

I appreciate all the information and advice, there is still always so much to learn. I'm currently in deep trying to prep, prime, and paint my boats trailer while the weather is abnormally warm the next few days but I might take some time while paint is drying to fire up the outboard and let it run with the seafoam in the tank and see what happens.. I got the whole boat, motor, and trailer for $350 so if the motor goes then I won't be hurtin too bad about it, but like to save money anywhere I can. And I've always liked the evinrude tilt lever!

 

[RaisedByWolves]

I appreciate all the information and advice, there is still always so much to learn. I'm currently in deep trying to prep, prime, and paint my boats trailer while the weather is abnormally warm the next few days but I might take some time while paint is drying to fire up the outboard and let it run with the seafoam in the tank and see what happens.. I got the whole boat, motor, and trailer for $350 so if the motor goes then I won't be hurtin too bad about it, but like to save money anywhere I can. And I've always liked the evinrude tilt lever!

Holy cow, did you have to wear a ski mask during that robbery?


Pics?

 

[nccatfisher]

I suggest you read through this post and maybe even type "decarb" in the search feature and look at what Pappy has recommended on other threads also. As I said earlier it MAY help your engine or it may not, it won't hurt it.

https://forum.tinboats.net/viewtopic.php?f=4&t=39239&p=402021&hilit=decarb#p402021

 

[WhopperPlopper]

Raised by wolves

Well technically I paid $150 cash along with a firearm I paid $200 for that was worth around $400, so only cost me $350. The waterline on the inside was nearly up to the back deck so was under water up on the bank for a long time, and all the foam is water logged. DOnt want to hijack my own post cause I do need help with my motor but you can check my restore “1983 lowe stinger pro”. Guy “owned it for about 8 months”
And realized he was over his head with this project.. so he floated the title lol

 

[WhopperPlopper]

Well I got out today to try and start this morning and at least try to get it warm to retest compression... started first try so I got a videoZzz yes I know no water shame on me but just for a sec.. compression now at 75 for both... Ive got a trash can and motor al
Rigged up on a stand so going to put some seafoam in the gas tank and let it run for a while.. is there a way to test for blown head gasket without it being on the bot and not have power?