Engine Replacement/Upgrade

[m4keyourself]

Hello all,

I've had my boat for 5 years now. It's a 2001 Glastron SX 175 with a Mercruiser 4.3 190 hp engine and Alpha One drive. Out of curiosity, I was wondering if full engine upgrades are something that people do? For example, if I wanted to replace the 4.3 with a 5.7 - is this something that's possible?

I'm not sure if I would actually do it, but I am curious about it. It might be something fun I'd like to do with my father some day now that he's retired and is always looking for a fun project.

If this is something that people do, how would one go about doing it? What are some things to look for when upgrading an engine? I would assume the first thing would be to make sure it's compatible with the Alpha One drive, but what else is important to look for?

I'm just thinking about a a possible fun project with my father on my older boat.

Thanks for any advice!

 

[tpenfield]

Yes, people do those sorts of things . . .

You would probably need a complete 'bobtail' engine, as there would not be much, if anything that you could use from the 4.3 engine.

Check out engine replacements on 'Doug Russell' and 'Michigan Motorz' websites.

 

[m4keyourself]

Yes, people do those sorts of things . . .

You would probably need a complete 'bobtail' engine, as there would not be much, if anything that you could use from the 4.3 engine.

Check out engine replacements on 'Doug Russell' and 'Michigan Motorz' websites.

Awesome, I'll do that. Thanks tpenfield

 

[kenny nunez]

Another source is Marine Power in Pontchoula , La. Check their web site.
They have distributors around the country.

 

[Rick Stephens]

Place to start is the engine installation drawings. That'll let you decide whether bigger motor fits.

Also, might have insurance issues if the underwriter thinks the hull is not designed for the larger engine. Most hulls in the 19 foot and up range usually have multiple engine options when built, if those include a 5.7 then you'd most likely be golden in supporting the upgrade.

 

[m4keyourself]

That's great guys, I really appreciate the help. I've had my boat for about 5 years now and an upgrade would be nice, along with a fun project. My father is a major gear head and I've picked up some tricks along the way, but doing some research beforehand and checking things out so I don't accidently end up going into something over our hands!

 

[Rick Stephens]

I'd also just consider upping the horsepower of your current motor some. Better intake and 4 barrel carb. Going to the 5.7 means adding at least 200 pounds that the extra horsepower is wasted pushing through the water. The 4.3 is really the perfect motor for a 17.5 foot 2100 pound runabout. You can probably get your performance up with better carburetor and intake by 30 HP or maybe a bit more. Not a massive amount, but significant in a 17 footer. You can also potentially prop better, add trim tabs, clean things up and maintain that great fuel efficiency the 4.3 gives you.

 

[Bondo]

Ayuh,..... Welcome Aboard,..... As Rick says, beefin' up the 4.3l is certainly viable,....

Goin' to a 5.7l would require replacin'/ regearin' the outdrive though,....

 

[Scott06]

The ease/feasibility of this swap will depend on if the boat was offered with a 5.7 or not. The 5.7 is is about 4.5" longer than the 4.3.

I did a 4.3 to 5.0 swap in a Sea Ray 200, it was relatively easy because the boat was built to have a V8 option (5.0 & 5.7 are physically same size engine). So there was 5" in front of engine and engine side mount stringers were sized so that both the 4.3 and V8 mounts would fit on there.

I didnt buy a bobtail engine, I got a partial engine plus exhaust manifolds from Michigan motorz-https://www.michiganmotorz.com/5-7l-vortec-marine-silver-package-315-hp-1967-current-replacement
I swaped over all the acessories and electrical componets from the 4.3, just got a 5.0 igintion module, some of the cooiling hoses,made a fuel line, and the exhaust down elbows. Doing this saved about $1500-2k off a complete bobtail.

I was able to keep the V6 -1.81 ratio drive an just step up from a 19" to 21" pitch prop. SInce a 5.7 would take a 1.47 drive its likely you may not be able to reprop around two drive ratio steps.

 

[Earl Cordova]

IMO if you don't like the motor, sell the boat and buy what you want.

 

[76SeaRay]

Bondo makes a good point on the Alpha One outdrive. I am scratching building my 5.7L Vortec and working to keep the horsepower no greater than 300hp since that is the spec limit on the Alpha One. Fortunately, my Alpha One has the right gear ratio (I am rebuilding it also) and the reason I say fortunately is that the gears for the gear ratio change are very expensive. Do some pricing exercises before you commit to a path. You might want to consider just replacing the drive when you replace the engine.

 

[Paintman1960]

I have a 383 making around 430 HP, Just gotta be careful coming up to plane , once yer rolling , yer good IMO

 

[m4keyourself]

I'd also just consider upping the horsepower of your current motor some. Better intake and 4 barrel carb. Going to the 5.7 means adding at least 200 pounds that the extra horsepower is wasted pushing through the water. The 4.3 is really the perfect motor for a 17.5 foot 2100 pound runabout. You can probably get your performance up with better carburetor and intake by 30 HP or maybe a bit more. Not a massive amount, but significant in a 17 footer. You can also potentially prop better, add trim tabs, clean things up and maintain that great fuel efficiency the 4.3 gives you.

Hey Rick, bouncing back on here to check out some of my threads. It's funny you mentioned this because this is actually mostly what we ended up doing! Runs so much smoother than before and was a breeze to accomplish, not to mention some quality time getting to know my own engine better. I'm definitely shooting for an boat upgrade in the future, but this certainly worked for our needs. Thanks for the input!

 

[m4keyourself]

IMO if you don't like the motor, sell the boat and buy what you want.

Unless you like your current boat, enjoy working on it, and tinkering with engines...