motor swap in a 91 Glastron 1900. 4.3l v6 to 7.4l v8(big block)

H

hassingermotorsports

Recruit
Joined
Aug 20, 2010
Messages
5
OK here is what I have. Got a 91 glasstron 1900 that needs a new motor and wet manifolds do to freezing , out drive swap wouldnt hurt either. also got a complete 454 and outdrive set up out of a damaged boat. both are alpha ones. anyone out there ever do a swap like this. I know it won't be a problem getting it all in the boat. It should be a fun go fast boat when it is done. what do you think. And I am not building this for my family boat. its just some thing I got all the parts for and thought it would be a fun run about when done.
 
45Auto

45Auto

Commander
Joined
May 31, 2002
Messages
2,842
Re: motor swap in a 91 Glastron 1900. 4.3l v6 to 7.4l v8(big block)

Lots of people have swapped big blocks into boats that originally had small blocks. What's wrong with using it for a family boat?
 
H

hassingermotorsports

Recruit
Joined
Aug 20, 2010
Messages
5
Re: motor swap in a 91 Glastron 1900. 4.3l v6 to 7.4l v8(big block)

way to small for me personaly. I just sold my wellcraft classic 200 to get a bigger boat( weekender style) this boat will just be dads play toy, go fast boat. and Oh dont worry I am sure I won't be ale to take it with out my boy.
 
AZSenza

AZSenza

Chief Petty Officer
Joined
Mar 11, 2008
Messages
521
Re: motor swap in a 91 Glastron 1900. 4.3l v6 to 7.4l v8(big block)

Your "Supposed" to obey the "Maximum Horsepower" Rating the hull was certified with. The real damger is if the transom can handle the added power and the mounts, the added weight of a 500Lb 454. Other than that, it should be fine and dandy fun.
 
H

haulnazz15

Captain
Joined
Mar 9, 2009
Messages
3,720
Re: motor swap in a 91 Glastron 1900. 4.3l v6 to 7.4l v8(big block)

Lol, that 454's gonna weigh more than 500lbs fully dressed, probably closer to 600+. I'm not sure it'll be that big of an issue, but that is a pretty big jump in weight over the 4.3L. Aside from making sure the bilge is deep enough to get the oil pan in and clear, I don't see much that should complicate things if you have the inner transom plate/motor mounts. You might want to beef up the front motor mount stringers as well to handle the extra weight.
 
H

hassingermotorsports

Recruit
Joined
Aug 20, 2010
Messages
5
Re: motor swap in a 91 Glastron 1900. 4.3l v6 to 7.4l v8(big block)

I have seen these boats with 5.0l and 5.7l's in them from the factory. So i figuerd going to a 7.4l wouldn't be that much of a jump in weight. from small block to big block, the big block only weighs at the most 200 lbs more. as for the hp rating on the boat. not sure what it is, but have already thought about that being the only hold up.
 
thumpar

thumpar

Admiral
Joined
Jun 21, 2007
Messages
6,138
Re: motor swap in a 91 Glastron 1900. 4.3l v6 to 7.4l v8(big block)

Isn't a 7.4l a little to powerful for an alpha drive?
 
Bondo

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,525
Re: motor swap in a 91 Glastron 1900. 4.3l v6 to 7.4l v8(big block)

hassingermotorsports said:
I have seen these boats with 5.0l and 5.7l's in them from the factory. So i figuerd going to a 7.4l wouldn't be that much of a jump in weight. from small block to big block, the big block only weighs at the most 200 lbs more. as for the hp rating on the boat. not sure what it is, but have already thought about that being the only hold up.
Click to expand...

Ayuh,.... But you can build Plenty of Horsepower with a Sbc, Plenty enough to Smoke an Alpha drive anyways,...
'n save that 200 lbs....
 
H

hassingermotorsports

Recruit
Joined
Aug 20, 2010
Messages
5
Re: motor swap in a 91 Glastron 1900. 4.3l v6 to 7.4l v8(big block)

they say the 7.4 is a bit much for the alpha drive. the 7.4l and alpha one is a complete stock set up out of a 23ft boat( got damaged over last winter, building fell on it and ruined the boat). I figured it lived behind it in the bigger boat, so the stress would be less pushing a smaller boat around.

and the only reason I am working on a swap like this is because we have all the parts on hand.
 
Don S

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: motor swap in a 91 Glastron 1900. 4.3l v6 to 7.4l v8(big block)

Mercruiser did use the 7.4 with an Alpha I drive, back in 86 thru 88. Then they invented the Bravo drive for 89.
The Alpha drives used were 1.32:1 gear ratio. The Alpha drives are rated for a max of 300 hp. The 7.4 carbed engines of that time were 330.
 
You must log in or register to reply here.
Top