Rebuilding a 1956 Evinrude 7.5hp

[chas56x]

I got this motor in a trade. I did a compression check, and the motor had low compression, so I decided to replace the rings. When I got the pistons out, I found that the connecting rod bushings were worn almost away. My question is does anyone have a good set of connecting rods that they would be willing to sell? Shoot me an e-mail at c.rathbun001@verizon.net…

[fleetwin]

You better measure the crank journals as well, new/used rods won’t last long on damaged/worn crank journals. Have you measured the cylinder bores and piston skirts?

[Mumbles]

Try placing an ad in the Free Classified section on these boards.

Damage like that to the rods and crank journals is more than likely caused by running the motor on a wrong fuel/oil mix. These motors plus the 5.5 horse models demand using a 16:1 fuel mix because of the bearing design in them. Running them on modern 50:1 or any other mix besides the required 16:1 is just asking for trouble.

[frankr]

An often overlooked cause of bearing damage in those motors is water ingestion into the cylinders. It is easy to blame the damage on oil because the results are similar. Two very common water entry routes are the carbon seal at the bottom of the crank/top if drive shaft, and pin holes in the exhaust cover baffle plate. I confess to missing those a couple of times and had to do the job over. But experience is a very quick teacher.

[William Jatzek]

Save yourself some money. That motor had a rough life. Just watch eBay for a 1956 Evinrude 7.5 complete power head. Look for one that is from the great lakes area or from a state far from salt water. They are on eBay quite regularly. You probably can pick one up for about $50.00. Bill,

[chas56x]

I measured the OD of the crank pin and it measured 0.0815 on both upper and lower crank pins. I then measured the ID of the connecting rods at the measured 0.0825 on both. This makes for a one thousandths of an inch clearance. I would think the clearance would be OK?

[dmbono]

that is more like 10 thousandths- way too much

[RICHARD A. WHITE]

agree with Dave Bono,that is not .001 but rather .01 as your rod journals could never be just under 3/32 of an inch in diameter

http://www.richardsoutboardtools.com
classicomctools@gmail.com

[Mumbles]

The book sez, the Fleetwin rod journal should mike out at 0.8120 – 0.8125. 😀

[Author]

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