Engine Replacement Compatibility

Scott06

Scott06

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Apr 20, 2014
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m4keyourself said:
I'll understand if the question is too broad and can't really be answered fully! I think Scott here has a lot of the information I'm interested in:

Scott,

This is fantastic information for me, thank you so much. This, I can definitely use if I do decide to do any more work on my Glastron in the future. Michigan Motorz seems to be a great resource for marine engines, and that's good to know that if I did swap to a V8 I would need more room in the engine compartment and need to move the blocks forward 4-5" more, and would need to also consider the exhaust headers, wiring harness, prop pitch, and ratio, in addition to the added weight of the engine.

I think, for the most part, this response contains most of the information I was looking for and can also be used in a broader sense when purchasing an engine for any boat. At least, some of the biggest considerations, that is.
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a 4.3 to V8 is pretty easy swap - one the exhaust manifolds are different and down turn elbows after the riser/elbow on top of the exhaust. Both 4.3 and V8 share the same wye pipe so pretty easy drop in. I kept my wiring harness from the 4.3 just swapped ignition modules as the 4.3 doesn't get as much advance. Drive ratio I think you can prop around one drive ratio step easily like I did. I think if you were doing 2 or more drive ratios steps you may run out of available prop pitches.

Having said that a 5.7 would be over kill for a 17 ft glastron... my buddy ahs a galstron 185 with same 43. you have very preppy hops on a plane quick and has a small wake that is nice for skiing. With a 4 bbl would have a nice punch

Bottom line start with smaller projects that are within your ability and cashflow...Nothing worse than starting something and not being able to use it for years. I was into classic muscle cars from when I was 15, had a nice '65 Pontiac LeMans coupe that had 66 k on it. All I wanted was a real GTO. Sold the LeMans, bought a 65 GTO convertible project car that was beat to hell, took me 30 years to get it road worthy. Wasn't fulfillable project until I was older, the wife was back in the workforce, kids were older and I made better money ...
 
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m4keyourself

m4keyourself

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Scott06 said:
a 4.3 to V8 is pretty easy swap - one the exhaust manifolds are different and down turn elbows after the riser/elbow on top of the exhaust. Both 4.3 and V8 share the same wye pipe so pretty easy drop in. I kept my wiring harness from the 4.3 just swapped ignition modules as the 4.3 doesn't get as much advance. Drive ratio I think you can prop around one drive ratio step easily like I did. I think if you were doing 2 or more drive ratios steps you may run out of available prop pitches.

Having said that a 5.7 would be over kill for a 17 ft glastron... my buddy ahs a galstron 185 with same 43. you have very preppy hops on a plane quick and has a small wake that is nice for skiing. With a 4 bbl would have a nice punch

Bottom line start with smaller projects that are within your ability and cashflow...Nothing worse than starting something and not being able to use it for years. I was into classic muscle cars from when I was 15, had a nice '65 Pontiac LeMans coupe that had 66 k on it. All I wanted was a real GTO. Sold the LeMans, bought a 65 GTO convertible project car that was beat to hell, took me 30 years to get it road worthy. Wasn't fulfillable project until I was older, the wife was back in the workforce, kids were older and I made better money ...
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You've made all the key points I was looking for, and I greatly appreciate it. Thank you for taking the time to share these things with. I agree that nothing can be completed without research, and is always always the most important step to take before making any decisions or purchases. I'm confident in my ability to research and learn new things, just not experienced enough to think of all the obstacles that would get in my way. That's where my idea to turn to this forum came in - because I knew I could rely on you guys to give me some really important key considerations if I start looking at a new project.

You all have been so helpful, thank you so much for your time and sharing your experience with me.
 
achris

achris

More fish than mountain goat
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May 19, 2004
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27,468
If you're referring to generational changes, you need to learn about the different drives (MC1, R, MR, Alpha One and Alpha One Gen II) and how they interact with the different engines. Learn about exhaust systems ('log', centre rise, dry joint). Learn about the different ignition systems (points, EST, Thunderbolt IV and V), and finally the fuel systems (mechanical and electric pumps, 'Cool-fuel' systems, 2 and 4bbl carbs, TBI and MPI)...

Yes, your request is very broad...

Chris.
 
m4keyourself

m4keyourself

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achris said:
If you're referring to generational changes, you need to learn about the different drives (MC1, R, MR, Alpha One and Alpha One Gen II) and how they interact with the different engines. Learn about exhaust systems ('log', centre rise, dry joint). Learn about the different ignition systems (points, EST, Thunderbolt IV and V), and finally the fuel systems (mechanical and electric pumps, 'Cool-fuel' systems, 2 and 4bbl carbs, TBI and MPI)...

Yes, your request is very broad...

Chris.
Click to expand...

Broad as it may be, this information is also helpful for me - so thank you. So far, though, my post has proven very useful to me even though it may seem broad to others.
 
Scott06

Scott06

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m4keyourself said:
Oh great, thanks. Where can I find the "stickies section" ?
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in top of mercruiser section - its the top two threads that are stuck there.

When you start to hone in on a project or have questions on specifics X boat Y driveline ....come back there is a wealth of knowledge that helped me with my project years back
 
m4keyourself

m4keyourself

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Scott06 said:
in top of mercruiser section - its the top two threads that are stuck there.

When you start to hone in on a project or have questions on specifics X boat Y driveline ....come back there is a wealth of knowledge that helped me with my project years back
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Ah ok, I knew that stickies referred to something on the forum. That makes sense, the pinned threads.

You got it. Thanks again, guys. I'll be back when I've drilled into a specific project. In the meantime, I've written down the key things to consider that I've learned from you all.
 
Scott Danforth

Scott Danforth

Grumpy Vintage Moderator still playing with boats
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m4keyourself said:
Oh great, thanks. Where can I find the "stickies section" ?
Click to expand...
every forum has topics that are stuck. these look like postit notes. best viewed by a computer and not a phone/mobile device unless you have desktop view on.
 
m4keyourself

m4keyourself

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achris said:
A lot of the information you're looking for is in the stickies section...
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Been spending time going through the mercruiser stickies section and the amount of information there is incredible, thank you for mentioning it. You're right, a lot of my questions can definitely be answered there . Thank you!
 
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