1978 45hp interchangeable with 1977 55hp?

[GoodnightGraphics]

So, I managed to let my 1978 45hp (456h8j) overheat and now the compression is a mess. So I am weighing my options.

Ideally, I'd like to send my powerhead off to be rebuilt. I found a service (TMS Powerhead Rebuilding Service) that says they can rebuild my powerhead, but this will cost close to $1000. If my funds were more abundant right now, I probably wouldn't look for other options.

However, funds are not abundant.

I found a 1977 55hp (559HJ) powerhead with good compression for about $100 plush shipping.
AND NOW FOR THE BIG QUESTION: Could I use this to fix my outboard? Would I end up spending just as much trying to buy 55hp specific parts?

I appreciate any input!

 

[jerryjerry05]

Re: 1978 45hp interchangeable with 1977 55hp?

Most parts will swap over.
If the 55 works??
Just change the motors and keep the 45 for parts.

 

[Frank Acampora]

Re: 1978 45hp interchangeable with 1977 55hp?

The 45 has a shorter stroke and smaller diameter bore. So, you can not use the crankshaft or pistons. It also lacks an extra exhaust spacer giving more exhaust chest volume to the 55. Other than that, everything is swappable from engine to engine.

 

[Nordin]

Re: 1978 45hp interchangeable with 1977 55hp?

Hey, WATCH UP......... that 55Hp is a twincarb engine. The 45Hp is a singlecarb engine.
1976 was the last year the 55Hp had singlecarb.
1977 the 60Hp became 55Hp and 65Hp twincarb engine with MAG II ignition.
The 45Hp 1978 and 55Hp 1977 are two complete different engines.

 

[GoodnightGraphics]

Re: 1978 45hp interchangeable with 1977 55hp?

The 55hp I found is JUST the powerhead. So it looks like I will pursue rebuilding the 45hp. It was my grampa's boat/motor so I'd like to keep it all original if I can.

Anyone had any experiences with a powerhead rebuilding service? Would a traditional machine shop work on marine engine also?

 

[GoodnightGraphics]

Re: 1978 45hp interchangeable with 1977 55hp?

So I just called my local machine shop and answered my own question. They do SOME work on outboard motors. He said they basically will bore the cylinders, but that's about it. I would have to do the build.

I have built a few auto engines before, so I'm tempted to go this route. So I guess my next question (i'm full of questions) is: Is there a good place to buy an entire rebuild kit for my motor? Pistons, rings, bearings. gaskets, etc?

Thanks again for humoring me.

 

[Frank Acampora]

Re: 1978 45hp interchangeable with 1977 55hp?

I don't think pistons and rings are available for the 45. You can try some of the sites for obsolete engine parts given in various other posts on this forum--I don't remember them myself.

If you can find a single carb 55 you can swap it onto your leg and an early Force 50 will also swap right in. I know that Pistons and rings are available from Wiseco for the Force 50 and since the single carb Chrysler 55 is the same bore and stroke they are also available for that engine.

The rebuild itself is not a difficult job:

However, you should be able to find a complete and running Force 50 for about the same price as rebuilding your 45.

It would help if you posted your approximate location in your replies.

 

[GoodnightGraphics]

Re: 1978 45hp interchangeable with 1977 55hp?

Thanks Frank. It's good to know I have those options.

I'm pretty close to Houston, TX.