1963 18hp and 1969 20hp same cyl head?

[BigB9000]

I have myself a 1969 20hp Johnson that needs a cyl head, and a 1963 18hp evinrude. think they are they same head?

in 1969 I know they were, but I can look up anything older than a 68 on shop.evinrude.com

 

[F_R]

Re: 1963 18hp and 1969 20hp same cyl head?

I have myself a 1969 20hp Johnson that needs a cyl head, and a 1963 18hp evinrude. think they are they same head?

in 1969 I know they were, but I can look up anything older than a 68 on shop.evinrude.com

Be very careful and pay attention to actual part numbers, not casting numbers. OMC built 18, 20, and 25hp motors by mixing and matching a variety of cylinder heads and pistons, among other things. The parts all look alike to the naked eye, but vary in things such as compression ratio.

Now, the motor in question, a 1963 Evinrude 18hp takes a part number 378557 cylinder head. How does that compare with the number for the 20hp you found?

 

[BigB9000]

Re: 1963 18hp and 1969 20hp same cyl head?

Now, the motor in question, a 1963 Evinrude 18hp takes a part number 378557 cylinder head. How does that compare with the number for the 20hp you found?

Part Number: 0381151

darn!


How did you look up your number? I figure if I could learn how to do that, I wont have to make as many topics

 

[1946Zephyr]

Re: 1963 18hp and 1969 20hp same cyl head?

The head off of a 25hp definately won't work, because they are made different for compression reasons.

 

[rjezuit]

Re: 1963 18hp and 1969 20hp same cyl head?

This is just my opinion, but if the older 18HP head bolts up, and the pistons do not hit the head or spark plug, all that it can do is increase the compression if the combustion chamber is smaller. This is usually a good thing from a HP point of view. Bolt it on loosely, and rotate the crank by hand. If it does not hit, it SHOULD work.

 

[BigB9000]

Re: 1963 18hp and 1969 20hp same cyl head?

This is just my opinion, but if the older 18HP head bolts up, and the pistons do not hit the head or spark plug, all that it can do is increase the compression if the combustion chamber is smaller. This is usually a good thing from a HP point of view. Bolt it on loosely, and rotate the crank by hand. If it does not hit, it SHOULD work.

sounds like a plan.

Expensive gasket to see if it might work though.

 

[1946Zephyr]

Re: 1963 18hp and 1969 20hp same cyl head?

An 18 or a 20 hp should be pretty darned close heads from 1959 to 1970. they are the same motor head and block wise. I think the extra 2 horses comes from carburetion. Just make sure they have the thermostat set up. All 20hps will be. The 18's are from '59 on.

The 25's have different heads, pistons and carbs, so stay away from those.

If the part numbers are different from the 18 to the 20, that may not mean anything. They have assigned part numbers to each motor for the parts. What you need to do is take your old head and match it up with the new one and make sure everything is identical. Check the cumbustion chamber, bolt pattern and water jackets.

What is wrong with your old head?

 

[rjezuit]

Re: 1963 18hp and 1969 20hp same cyl head?

BigB, If you bolt it up loosely (a little tight) and don't run it, the gasket will be usable. I have reused head gaskets on a lot of small engines that have been run and had no problem. Rick