64' e-rude low compression in one cylinder

I've searched the forums and am still looking for a little bit more info. engine is a 1964 evinrude 90 horse starflite 90-2. model 904935 serial E03005.<br />After compression test my number 1 cylinder is 93, 2@89, 3@50 and 4@90. so i have one bad cylinder. what am i looking at as a cause. also what's it gonna take to get it fixed up a good like the others price wise and labor wise. I know this is an outdated engine i have heard that story from a lot of people here so dont just tell me to buy a new one, i dont want to . thanks.

Re: 64' e-rude low compression in one cylinder

Give her a decarb and check again, Ranger. With 50psi it could just be some coking.<br /><br />Good luck.

Re: 64' e-rude low compression in one cylinder

Hard to say what the cause is Ranger without taking a peep at the cylinders first and seeing what's in there. May be scoring, scuff or maybe just stuck ring.<br /><br />Did you recheck the compression to make sure it was an accurate read?<br /><br />A decarb may help....some.<br /><br />You could also pull the bypass cover on number three cylinder and look at the walls and maybe get some idea of the shape of the pistion and rings.<br /><br />The shape of all the cylinders will be a big factor in the final cost. If the cylinders are still in spec and can be honed and new rings install, that will help the final cost as oversize pistions aren't cheap. And I'm not sure what your local machine shop would charge for boring.<br /><br />But....all that is still in the air until we know what the holes are looking like.

Re: 64' e-rude low compression in one cylinder

Getting that engine up, and running would depend on how thick your billfold is. Electric shift, 4 into 1 carb, inboard mounted junction box for the alternator, control box. When done! you could'nt give it away. I understand, this is not what you want to here, just the way it is.

Re: 64' e-rude low compression in one cylinder

i have the controler to the electric shift and the unit does work. I have tore doen the carbs soaked and cleaned and put back together. eleminated the junction box by replaceing the parts in it with some after market ones, worked out pretty well, i would have purchased the junction box itself but kind find the ancient thing anywhere. That number 3 cylinder with the low compression also had a heli-coil fix in it, so i'm thinking its a good idea to pull that head off and take a look at what's going on in there and while i'm at it replace that head with one from a parts motor. I'm wondering if i didnt get that compression tester in there tight enough because of the heli-coil.. any thoughts?

Re: 64' e-rude low compression in one cylinder

I pulled the head today, but before that i took and spryed some wd-40 in the cylinder and turned it over with a fresh battery on it, i got a much better reading at 80 psi, i also found that i couldnt get the presure gauge on tight enough to get a good seal, mostly because of the heli-coil, i could see and hear the WD being sprayed out as i turned it over.<br />I got the head off with a minimal amount of work, the bolts didnt seem tight enough so i will make sure to torq to spec on re-build. the cyclider walls are glass smooth with no scoring that i can see, they look really good. <br />I found a parts motor that i will be pulling the head off off to replace so i dont have the heli-coil problem anymore.<br /><br />>How can i go about cleaning the tops of the pistons without hurting anything?<br />>What else should i be looking for while the head is off?

Re: 64' e-rude low compression in one cylinder

Once you get the new head back on (which seems like it could be a part of the problem)do a decarb. That should get most of the carbon off. Just make sure you use a lot of it, 2 cans min and let it sit overnight.<br /><br />edit<br />And keep checking compression