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Mercruiser 165 replacement alternatives

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PeterDE

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The Mercruiser 165 engine on my 1972 Sea Ray finally went to the big junk pile in the sky. Not bad for a 46 year old engine that has never had a major repair. But the cost of replacing it is way out there. A rebuild would cost 5-6K (parts labor, etc) Re-manufactured engine runs in the same ball park with the engine alone costing far more than the boat is worth. Marinizing a GM 250 (lots of them available) from an old pickup is an option but the costs are still out of my budget reach. (Don't get me wrong. I love my vintage boat and have a lot of sweat equity and cash invested in it) So I have been looking for a good condition, running 165 that I can drop in, hookup and motor away. I have found some but they are always on the wrong coast or the shipping costs would outstrip the cost of the engine. Haven't found one in good condition here in the PAC NW. Have found some but usually they are worn out and have the same problems mine has.

So for my question:

I have seen a lot of Mercruiser 3.0 (4 cyl) GM engines available out there. Would this be a big headache to install? Would it bolt up to my sterndrive (an Alpha)?
Considering how I use this boat 135 HP would be fine. Mostly I just go fishing and speed is not a priority. I don't pull water skiers or tubes so I don't need a lot of torque (like the 165). The boat is rather heavy for it's size but I don't see that as an issue. This engine would certainly improve fuel economy. Any thoughts? Anyone ever done this? In the meantime I'm still looking for a 165. Time is not an issue. I'm retired. I have a lot of time to do this. Just not a lot of money.
 
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Would likely need to change the reduction ratio in the drive as well... 6 cylinder engines and 4s typically have different reduction ratios.
 
I just checked this site's parts for your 165. it has a 1.65:1, 24-24 input gear ratio http://www.marineengine.com/parts/m...irve-shaft-housing-assembly-and-gear-assembly.

You can pull the top cover on your drive, sharpie a tooth on the input gear and drive pinion, give the gear one full crank and see if the pinion returns to the same place. I've read on forums the 3.0L has a 1.62:1 ratio, also 24-24 input ratio. So it should be close enough for the 3.0L, depending on it's power.

If your WOT tach. comes up above or below the max 4800 rpm engine speed with the 3.0L you can pitch up or down (approx. 200 rpm/inch of prop pitch) to get the engine torque where it needs to be. If it is too poochy to get up on a plane, you can pitch down, but you need to manually control the throttle to keep the engine under 4800 rpm.

I'm guessing the 165's flywheel hsg/engine coupler/gimbal plate engine mounts should line up on the 3.0L on your boats gimbal plate. The front mounts could be a different story. It looks like your 165 has a single center front mount and leveling adjuster. I don't know if this will transfer to the 3.0L. If not, go to this site's engine mounts for a 3.0L and see if the dual front mounts could attach to your new 3.0L and your boat's stringers.
 
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At this point I am just exploring the idea. The old engine is still in the boat partly disassembled.

I too think that I would have to make new mounting points for the front mounts. But my real concerning is what you said.
I'm guessing the 165's flywheel hsg/engine coupler/gimbal plate engine mounts should line up on the 3.0L on your boats gimbal plate.
Click to expand...
 
Ayuh,..... If ya got the space, a 4.3l is a better swap,...... it'll run on the gear ratio ya got now,.....

The Merc I-6 went outa production in '80, or '81,..... they ran the MC-1 drives, not the Alpha 1,..... different rear motor mount spacin',....

The 3.0l would drop in, but be seriously down on power, 'n dependin' on the pitch of the prop on it now, ya may not be able to reprop to make up the difference in gear ratios,....
 
If you're still looking for your engine, I have a Mercruiser 165 for sale, 1964 or '65 I think, was factory remanufactured by merc and has zero hours on it but has sat shelved for about 10 years.
 
$300.00 for the engine. The install cost about 10 times that. I bought it from a man who was converting his boat to outboards and he simply wanted to get rid of it. The rental of a pickup and a trip from Lacey Wa to McMinnville Oregon and back added another couple hundred. The repair shop that installed it is top notch on old boats and did an excellent job installing it. Unfortunately 2 years later the drive went (burned up due to loss of lubricant). Other things intervened ( like the pandemic, my son came down with parkinsons, and some other things) and the boat has been sitting in storage for two years. Eventually I will get a new drive, but it's not in the cards right now, or sell it to some other person who likes working on vintage boats.
 
I have the correct outdrive for your 160/165 I6 (1.65:1 ratio). Last run 22 years ago. It has been resting in dry storage. Would cost a trip to Seattle and a six pack of Anchor Steam beer.
 
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