Engine Replacement Compatibility

[m4keyourself]

Hello friends,

I hope everyone is having a safe and fun boating season! At some point down the road, I'm sure I'll be doing a boat renovation and I just had a question in anticipation of that (and also if anything should happen to my current engine).

If someone was looking to replace their engine, what are the most important points to look for regarding compatibility?

I'm really trying to learn as much as I can. I know that it needs to be compatible with the outdrive (Alpha One Gen 1, Gen 2, Bravo) size (for engine mounts and engine compartment) - but what are maybe 3-5 other key things that are important to consider?

I'm really wondering this in the pursuit of knowledge, since I like to be prepared in the event of something happening. I know some about engines, but not super-experienced, and I always like learning. There are some really nice looking marine engines out there on the internet for purchase from websites such as BluePrint Engines, Michigan Motorz, etc... and I'd love to know what needs to be considered while dreaming about buying one.

Thanks for any thoughts!

 

[achris]

With so many different engines on the market it's impossible to give you a generic list. Tell us what engine you have and we can point out the variations to be aware of...

Chris...

 

[m4keyourself]

With so many different engines on the market it's impossible to give you a generic list. Tell us what engine you have and we can point out the variations to be aware of...

Chris...

Sure, Chris - thanks!

For the past 7 years I have a 2001 Glastron SX 175 with a Mercruiser 190 HP 4.3L w/ Alpha One drive. I don't plan on selling this boat, but I will be buying a new boat within the next few years as the family continues to grow. Once I buy a new boat, I'll probably begin playing around a little more with the Glastron engine and carburetor just for fun projects and experience.

 

[achris]

The V6 comes in quite a few variations. Here's the basics...
Originally (1984-1992). Non-balance shaft, fluid mounts, non-vortec heads. 2bbl was a Mercarb or Rochester, 4bbl was a Rochester quadrajet. TB-IV ignition.
Gen II (1992-mid 1996). Balance shaft, rubber engine mounts, non-vortec heads. 2bbl was a Mercarb, 4bbl Weber or Quadrajet.
Gen + (mid 1996- end of life). Balance shaft, vortec heads, serpentine belt. 2bbl carb (with Thunderbolt V ignition), throttle body injection or multipoint injection. After about 2002 dry joint exhaust system.

Chris...

 

[itsathepete]

If you replace the engine make sure it is a vortec. If you decide to upgrade to a 4 barrel, you will need a 4 barrel vortec intake to fit square or spread bore carb of your choice.

 

[Scott06]

Sure, Chris - thanks!

For the past 7 years I have a 2001 Glastron SX 175 with a Mercruiser 190 HP 4.3L w/ Alpha One drive. I don't plan on selling this boat, but I will be buying a new boat within the next few years as the family continues to grow. Once I buy a new boat, I'll probably begin playing around a little more with the Glastron engine and carburetor just for fun projects and experience.

I assume you are looking to hop it up a little ?There's a couple ways you can go with this.

The alfa drive is capable of 300 hp and often times guys run 383's in front of them with decent life.

You have a very good base engine being vortec -a simple carb, intake, and maybe cam up grade would get you 220+ hp, probably just need to increase prop pitch keep the same drive.

I repowered a 21 ft sea ray that I bought with a cracked block - had the same 190 hp 4.3/Alpha G2 you have. The 4.3 and 5.0/5.7 SBC have the same front and back to the engine block. So swamping a V8 is easy if the engine compartment is long enough. you need 4-5" more in front of the engine, which also means the side engine mounts will be 4" further forward. The engine mounting stringers may or may not be long enough, my boat was offered with a V8 so I just needed to drill holes for mounts .

I got a partial engine package plus exhaust manifolds from Michigan motorz -I was able to keep all my accessories , wiring harness, coupler etc off the 4.3. I bought a 5.0 ignition module , some cooling hoses, exhaust down turn elbows off a V8. Kept the 4.3 ratio 1.81 out drive and stepped up 2" in prop pitch to compensate. If you go with an edlebrock carb the merc throttle bracket off a 357 alpha/bravo makes a nice clean factory install.

Bottom line hoping up your 4.3 is easiest, V8 is possible if you have engine bay room. Just need to keep in mind if you really go up in power that the hull may not be designed to go much over 55 mph and keep in a straight line... vs some of the more go fast boat designs.

 

[Rick Stephens]

We're talking a 17 foot boat here.

 

[Lou C]

17 foot boat a 4.3 bbl is more than adequate, and will fit in the available space...

 

[Bondo]

We're talking a 17 foot boat here.

Ayuh,.... That just means ya need a 350, if ya can't swing a 383,.....

 

[Rick Stephens]

I have only a glimmer idea how insurance liabilities play into this. I swapped a 3.0L to a 4.3 in a 17 foot boat. Insurance company was interested in whether the hull was designed for that. While the manufacturer offered this model with a 4.3, and the insurance didn't actually require me to prove it, the implication was there that exceeding hull power capacity would potentially place liabilities back on me. In the event of a major claim, might not have insurance that sticks.

 

[Lou C]

Also not sure if the extra 100 or so lbs of the V8 vs the V6 will lower the stern of a boat that size too much, could cause back wash in the exhaust problems.

 

[Scott06]

We're talking a 17 foot boat here.

That's why I made the comment about hull may not be designed for it. If he already has a 4.3 not sure what he was thinking about swapping in.

 

[Searay205]

It may sound fun to have excessive power but an unstable boat at high speeds (above 55) sucks, its not like playing in the ice with a car wihere you can kind of control the amount slide. On the flip side an underpowered boat sucks also just safer.

 

[Scott Danforth]

For the 2001 vortec with a 2 barrel carb that you have. Swap to a 4 barrel intake and carb. Add a carb spacer to help increase plenum volume. You are looking at 210-220hp at prop

 

[Scott06]

For the 2001 vortec with a 2 barrel carb that you have. Swap to a 4 barrel intake and carb. Add a carb spacer to help increase plenum volume. You are looking at 210-220hp at prop

Some one mark the date down, this is the first time Scott didn’t recommend a stroker …

 

[Rick Stephens]

Some one mark the date down, this is the first time Scott didn’t recommend a stroker …

Yeah, but he wanted to.

 

[Scott Danforth]

Some one mark the date down, this is the first time Scott didn’t recommend a stroker …

its a 4.3, the only good stroked crank for a 4.3 is $3500 for that forged beauty

however a supercharger for a 4.3 is only about $2500

 

[m4keyourself]

Hey everyone, sorry for the delay in writing back - there was a lot going on at work yesterday.

I'm very appreciative of all the responses I've gotten - you guys are a great help! Going back to my post- that's right, it is only a 17 foot boat, and I'm not looking to do anything extreme. To be honest, I'm not even specifically asking about this boat, particularly.

I've had the engine pulled before and rebuilt and cleaned and it's a perfectly good engine and in great shape. Switching to a 4 BBL carb and intake manifold would by far be the easiest upgrade. Though, that's not really what I'm interested in here.

Perhaps I should try rephrasing my inquiry - all I want to know is, in general, when you're renovating a boat and/or needing to replace the engine of really any boat, what are the biggest factors that need to be considered.

Example: Say I buy an older used boat that doesn't even come with an engine but still has the drive and I want to work on it in my off time to renovate and learn from and as a hobby. I'll have to purchase an engine for it. What are the most important considerations when looking for engines for it?

 

[m4keyourself]

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:

I assume you are looking to hop it up a little ?There's a couple ways you can go with this.

The alfa drive is capable of 300 hp and often times guys run 383's in front of them with decent life.

You have a very good base engine being vortec -a simple carb, intake, and maybe cam up grade would get you 220+ hp, probably just need to increase prop pitch keep the same drive.

I repowered a 21 ft sea ray that I bought with a cracked block - had the same 190 hp 4.3/Alpha G2 you have. The 4.3 and 5.0/5.7 SBC have the same front and back to the engine block. So swamping a V8 is easy if the engine compartment is long enough. you need 4-5" more in front of the engine, which also means the side engine mounts will be 4" further forward. The engine mounting stringers may or may not be long enough, my boat was offered with a V8 so I just needed to drill holes for mounts .

I got a partial engine package plus exhaust manifolds from Michigan motorz -I was able to keep all my accessories , wiring harness, coupler etc off the 4.3. I bought a 5.0 ignition module , some cooling hoses, exhaust down turn elbows off a V8. Kept the 4.3 ratio 1.81 out drive and stepped up 2" in prop pitch to compensate. If you go with an edlebrock carb the merc throttle bracket off a 357 alpha/bravo makes a nice clean factory install.

Bottom line hoping up your 4.3 is easiest, V8 is possible if you have engine bay room. Just need to keep in mind if you really go up in power that the hull may not be designed to go much over 55 mph and keep in a straight line... vs some of the more go fast boat designs.

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.

 

[Scott06]

Hey everyone, sorry for the delay in writing back - there was a lot going on at work yesterday.

I'm very appreciative of all the responses I've gotten - you guys are a great help! Going back to my post- that's right, it is only a 17 foot boat, and I'm not looking to do anything extreme. To be honest, I'm not even specifically asking about this boat, particularly.

I've had the engine pulled before and rebuilt and cleaned and it's a perfectly good engine and in great shape. Switching to a 4 BBL carb and intake manifold would by far be the easiest upgrade. Though, that's not really what I'm interested in here.

Perhaps I should try rephrasing my inquiry - all I want to know is, in general, when you're renovating a boat and/or needing to replace the engine of really any boat, what are the biggest factors that need to be considered.

Example: Say I buy an older used boat that doesn't even come with an engine but still has the drive and I want to work on it in my off time to renovate and learn from and as a hobby. I'll have to purchase an engine for it. What are the biggest things I should be considering when looking for engines for it?

Biggest things to consider are space in engine bay as that would be a lot of work to move rear seats make a new cowling etc . Anything can be modified but then your working on the boat not using it. So if you are purchasing a boat make sure it can fit your long term needs somewhat easily.
In 2015 I had a 17 ft Sea Ray 170 /3.0L, I was gonna swap in a 4.3 but the boat was really getting too small as my kids got bigger and would have needed a new doghouse for the 4.3. I bought a 21 ft seay ray 200 sport/4.3 190 hp with only 37 hrs on it, PO cracked the block so it was a handyman's special. Because the 4.3 and 5.0 share a common lineage (block is the same front and back minus 2 cylinders) and the boat was offered with a 5.0 from the factory (stingers set up & engine compartment had the room for longer block) it was a clean bolt in swap. I spent a lot of time reviewing parts drawings to see what could swap over from the 4.3 to 5.0 which saved about $1500-2000 to mix and match what was needed vs buying a complete bobtail engine. I kept the same drive with the V6 ratio just stepped up in prop pitch which is also a consideration, but it is easy to swap uppers if needed.

On an older boat biggest thing to look at is condition of stringers , floor, and transom. Repairing that can be more costly and definitely more time consuming.