Evinrude 33hp coil gap.

[Bulkster]

I have an old evinrude 33 hp. i just wondering about the gap betwen the coil and the cylinder. i now have 0.40 is that to much? the compression is 100psi is that enough?? <br />/KIm

 

[Bulkster]

Re: Evinrude 33hp coil gap.

The engine is from 1965..

 

[Paul Moir]

Re: Evinrude 33hp coil gap.

100psi is excellent, provided that both cylinders are with 10% of each other. If one reads 100 and another reads 112, that's too much of a difference.<br /><br />By coil gap do you mean the gap between the ignition coil and magnet under the flywheel?

 

[Bulkster]

Re: Evinrude 33hp coil gap.

Sorry the right word is pistons. i wonder if the gap betwen the pistons in the cylinder and the cylinder wall is to big (o.40). i think it maybe to big but the engine sounds god and runs god. so should i worry about it or let it be?<br />/Kim

 

[Paul Moir]

Re: Evinrude 33hp coil gap.

Ok, I get it. My manual lists the acceptable piston to wall gap as .0030 minimum to .0450 maximum. That must be a misprint! It must mean 0.0030-0.0045" (.076mm-.114mm)<br /><br />If you mean there's a gap of 0.040" inches (1mm) between the piston and the wall, I would suspect the engine had been bored 0.040" oversize, but standard pistons installed!<br /><br />EDIT: Sorry I'm a bit confused. You get 100psi compression and you have a piston to wall clearance of 0.4mm?? I would think you couldn't have both! How did you measure the gap? Did you just rebuild (overhaul) the engine?

 

[Bulkster]

Re: Evinrude 33hp coil gap.

I took of the cylinder head and realized that i can move the piston side to side a little in the cylinder. when i pushed the piston max in one direction i had about 0.30-0.40 mm gap. That must be 0.15-0.20mm gap at both sides?. And the maximum gap is 0.14mm at both sides? the cylinder walls looks pretty nice. The engine did no funny noises when i had it starded. The compression is around 90-100psi at both cylinders.

 

[Bulkster]

Re: Evinrude 33hp coil gap.

are you sure its a print misstake. Dont you think that 0.076mm-1.14mm maybe acceptebel in a so old engine.

 

[G DANE]

Re: Evinrude 33hp coil gap.

Hi Evinrude 33, How are you across Øresund ?? You cant mesure piston clearance at the top. The piston top expands much more than skirt, Piston clearance on a cold motor at top is shocking if you are used to work on cars. Put a piston ring in it, correct it using a piston skirt to push it a little down and mesure ring gap. then you will know wear. But with compression on 100 you have no problems.

 

[Paul Moir]

Re: Evinrude 33hp coil gap.

I understand. No, I was able to confirm that .14mm is the maximum gap. Normally you measure it by removing the piston, measuring the diameter of the piston at the skirt, and subtracting the cylinder diameter. The 'skirt' is the bottom part of the piston. You measure it there because the piston is actually tapered, so the top is smaller than the bottom. When it heats up, it expands at the top and becomes cylindrical.<br />If you have good compression like you say, and it runs good and there's no noises, I wouldn't worry at all. If the piston was really loose you would here piston 'slap' from the skirt striking the side of the cylinder. Besides, there would be evidence of damage on the cylinder wall. I take it there was no large ridge formed by the piston rings at the top of the cylinder?<br /><br />Do not underestimate these old engines, they are very precise! When I was double-checking that piston to cylinder clearance number, I noticed OMC widened the tolerances on a bunch of their engines in the early '60s. That was just when they switched to 50:1 from 24:1.<br /><br />Good luck!<br />EDIT: Sorry GDANE, it looks like we had a posting collision.

 

[Bulkster]

Re: Evinrude 33hp coil gap.

Thanks alot for the answers. I just wanted to be sure. the other engine parts like ignition and gearhouse works wery nice no bad bearrings or anything like that, so i think it maybe a good engine for my little DC (3.75m) so thanks again.<br />/kim <br />P.s Weather was fine across the bridge of öresund today...