Are these readings too low(compression test)

[outlawfox13]

I went to go check out an old evinrude 40hp(1962 model 35530) I checked everything on it and all seemed well, even the lower unit was in good shape(I pulled the skeg and the gears looked great) , except that the compression test revealed 80 psi on the top cyl and 90 on the lower. I though this was too low, is it? Also this motor has not ran in a few years. Any advice would be nice, thanks Mike

 

[castires]

From my knowledge you want at least 90.

Add 2 teaspoons of 30 weight motor oil in the cylinders and redo the compression test.

If there is a dramatic, more than 10-15 psi increase, then the rings are bad.

 

[1946Zephyr]

Re: Are these readings too low(compression test)

If the motor hasn't ran in a few years, I would get it running and then re-take the compression test. An hour of running will get fresh new fuel mix in there and get things lubbed up again. It wouldn't be a bad idea to sea foam the motor too. 1962 and later 40's were built differently than the previous model years. They beefed up the crank and made it a lower compression motor. I happen to be a proud owner of one of these and a few others.

 

[HighTrim]

Re: Are these readings too low(compression test)

I had a 35530 once and I seem to recall it having in the 100 psi range. Ran fine.

EDIT: More thinking about that motor, I think It had about a 10 to 15 psi difference as well. Faulty head gasket. Changed it out, dressed the head on a piece of glass, Decarb like Zephyr stated and she was much healthier compression wise.

 

[outlawfox13]

Re: Are these readings too low(compression test)

So do you think for a hundred bucks its worth it? Or try the oil method first ? I would really like a larger motor on my boat, but im not looking to lose out on too much money. Also the plugs looked good, no fowling or what not. Acctually they looked like one of my spark plugs after running.

 

[boobie]

Re: Are these readings too low(compression test)

Do as Zeph said above and do the sea foam trick or else use BRP Engine Tuner. I've had good luck with that as far as freeing up rings.

 

[HighTrim]

Re: Are these readings too low(compression test)

You are probably ok at that price.

Im really surprised he let you pull the skeg! Im pretty helpful when selling a motor, but I dont think Id let someone pull the gearcase apart without a down payment. If they decide no, Im stuck resealing the thing.

 

[nwcove]

Re: Are these readings too low(compression test)

you cant go wrong for the money,you say you want a bigger motor, tune up and trade up!

 

[outlawfox13]

Re: Are these readings too low(compression test)

The reason i pulled the skeg was because the motor would not go in neutral, so i checked the shift linkage and it moved so i knew somthing was up with the shifter(it was slipped off the clutch dog, someone removed the pin, and moved the selector). So we had to check, plus it needs a new seal. Thank you for all of the advice i really appriciate it.
I think i will go get it.
Mike

Edit: If the motor is bad, then I could strip it and sell it, plus I am pretty sure the controls will work with my 73 Johnson. But I wonder if the starter will work as well? because if so I can part the motor out and still be fine.

 

[1946Zephyr]

Re: Are these readings too low(compression test)

Those motors are pretty forgiving and very reliable. $100 is a good deal. You may have to tune it up, but it'll be worth the effort. I happen to have one this particular model year and same model number. I'll check the compression on mine this weekend and let you know what I get, so you'll get a good ball park figure on it.

 

[outlawfox13]

Re: Are these readings too low(compression test)

Thanks Zephyr, I would really like to see the readings. I ended up picking it up last night, and will dive into the motor later this week or after the hollidays. Right now I need to look for a steering application(either cable/pulley or teleflex style). Also I will need to know how to install all the wiring(to the battery and what not). I think I may repaint it to match the color of my boat. Since yall may want to see the boathere is some eye candy. I'll get some pics of the motor tomorrow.

 

[1946Zephyr]

Re: Are these readings too low(compression test)

Well, I just took a compression test on my motor and I got 112 on the bottom and 108 on the top, 6 pulls with the hand starter. This motor I just started it about a week ago and did so with the hand starter and it idles good.

 

[HighTrim]

Re: Are these readings too low(compression test)

I have a '58 35hp Lark that there is NO way you could start it manually, so much compression. Tuned well. Ill have to tinker a little more, maybe the compression reliefs arent working.

It has 140 psi in both holes, and you can only get one "thump" out of her manually. She needs a GOOD strong battery, and I had to install brand new 4 GA welding cable for the Battery Leads.

Give her a good decarb and let us know if it helped.

 

[1946Zephyr]

Re: Are these readings too low(compression test)

Yea, my '58 Lark has 130 per cylinder and I got that with 6 pulls on the pull rope. It started pretty easy with the rope too, just like the other two bigguns. Fortunately, my '58 and '61 have the compression releases that knocked the compression down to about 80 for hand starting. LOL

 

[outlawfox13]

Re: Are these readings too low(compression test)

Thanks for that Zephyr, I will try and get her running this week, then do a decarb after I ensure she runs well. Thanks again everyone!!