Can I swap Mercruiser 165HP inline 6 with Maercruiser 180HP inline 6?

[mstang64bb]

I have a 1974 Mercruiser 165HP inline 6 with a cracked block. I have not have much success in locating another Mercruiser 165HP engine or engine block from a truck. I did find a 6 CYL MERCRUISER engine 4.0L 180 HP on Ebay that I can pick up. My question is will it fit? Would I be better in finding a 140HP 3.0 instead?

 

[Scott Danforth]

welcome aboard

mercruiser did not make a 4.0. the 4.1 is a 250 cubic inch, which is what your 165hp motor is.

stay away from the mercruiser 3.7 liter 4-cylinder (called the 170, or 470 or 480)

 

[Rick Stephens]

I think you will find the gearing is too high in your outdrive for a 3.0L. If the prop you are using is high enough pitch you might be able to replace with a lower pitch prop to compensate. I'd say your current setup would have to be a 19 in pitch to be certain you have enough choices in lower pitch props.

Best is to find a replacement block. Has to be findable. They were common as dirt back when.

 

[mstang64bb]

The engine I found on Ebay is a Marine Power SportPac 250. It is an inline 6 with 4bbl carb making it 180HP, my guess. I could not find any info on this brand of motor. I'm pretty sure it's a GM 250 block. Do I need an early vintage engine, or would a later model work as well?

 

[Bt Doctur]

that one should be a bolt in your housing should bolt right up as long as the flywheel dia is the same