1973 Crestliner Muskie Tri Haul 17' engine/stern advice

[awright112000]

Hello,

My 1973 Crestliner had a 2.5 L Mercruiser in it and block cracked. I picked up a 1981 3.0L engine and outdrive. I had the machine shop do valve job and magnaflux and I replaced most external parts with like for like except upgraded to electronic distributer.

Questions:

I haven't dropped the engine in boat yet, is the exhaust riser going to be the same? Only difference I notice was the rubber piece is compressed on the 3.0 where the 2.5 is not.

The engine mounts are different but appear to be the same height?

The outdrive I acquired with the 3.0 appears to be in better shape but it has flat top, my 73' has the lifting eye so I am guessing I have a pre alpha and the 81 is a alpha 1 gen 1. What mods do I need to make to use the alpha one or should I bother at all?

Thanks!

 

[wahlejim]

I can only speak about mine, I am sure others will be around to correct any mistakes I make on this. You likely have an MC-1 drive on there now. My MC-1 drive was replaced with an Alpha One with minimal changes. Serial numbers will help determine compatability. If you could put the serial number of the new engine, old drive, and new drive you will get a much better and more detailed answer. In my opinion, with the new engine, I would do what it takes to put an alpha on there. However, you do want to verify it is an alpha and not an MR.

In regards to exhaust risers, you want to get I believe 18" above the water line when mounted in the boat.

achris has a diagram he shares that shows what to look for with risers and mounting height. Others will be around to give a much more detailed answer on what it would take to mate the engine and drive together with what you have, but serial numbers will go a long way in determining the best matchup.

 

[achris]

'73 and '81 are both MC1, so mounting the engine won't be a problem. Both engines use the same drive ratio, so they are interchangeable. The flat top on the new drive indicated either R, or MR/Alpha One (structurally, MR and Alpha One as the same, the difference is only marketing). You'll be able to tell which when you split the drive to service the water pump. If the top of the drive shaft has a pin, it's an R, no pin it's an Alpha One.

This is what you're looking for... (Note: they call out 'MC1' and 'Alpha1'. 'MC1' includes 'R', 'Alpha1' includes 'MR')



​​​​​​​Your exhaust elbow heights are the same between engines, but as the exhaust elbows are different. You may need to change the pipe (between the elbow and the transom assembly) and the upper bellows (immediately below the elbow)... Could you get those parts from the boat you got the engine and drive from?

Chris......

 

[awright112000]

Awesome info thanks.

Now that I have everything put back together, would yall recommend starting it on the cart(external-battery/fuel/start switch) or drop in boat and fine tune everything?

 

[achris]

Start it on the cart, and add 'water' to your list.