Repower '82 Merc 305

[BearlyFunctioning]

I need to repower my stock 4 barrel 305 Merc (cam lobe whent flat) in my 6500 lb ,loaded (scale wt) 1982 Sea Ray.

Looking into doing a 350 with vortec heads. My main question is about carb height changing. How much will it change with vortec heads ?

Is there a intake that doesn't raise the carb ? My engine is under the aft deck of the boat, no room to raise the carb.

The engine has a closed cooling system, suggestions for intake manifolds with or without vortec heads that would work with my height restrictions would be appreciated.

How much is to be gained, torque wise, with an aftermarket 4 barrel vs stock 4 barrel with non vortec heads ?

I'm Looking to be able to use my 17" ss prop loaded @ 6500 lb. Right now I can only pull 4200 rpm empty @ 5500 lb. How much more engine do I really need from what was a good running stock engine ?

 

[Fishermark]

I don't think the height is affected with Vortech heads - at least not noticeably. There is a whole variety of intakes, etc you can use. The Vortech 350 is your best bet and bang for the buck.

 

[Bondo]

Ayuh,.... The intake ports on the Vortec heads are .200" higher, but carb height on the manifold oughta be the same,....

with closed coolin', an aluminum intake is possible, 'n the choices are mind bogglin',...

Yer carb question don't make alota sense, a 4 bbl. carb whether original or after market is the same carb,...
Yer's is probably a Quadra-jet, Merc now uses the Merc/ Weber/ Carter clone, same carb as the Edlebrock 1409, 'n 1410s,...

 

[BearlyFunctioning]

I see my question was incomplete on the 4bbl. question. I was asking about the intake manifold, stock vs aftermarket on the non vortec heads, is there much to be gained ?

This is my first repower, still don't know how far I am going to go in the quest for more from stock.

If the carb doesn't raise noticeabley from stock using vortec heads I can go that route, the question then becomes how much more engine do I really need to use my 17" prop ? If I have given enough info ?

 

[Bondo]

I'm Looking to be able to use my 17" ss prop loaded @ 6500 lb. Right now I can only pull 4200 rpm empty @ 5500 lb. How much more engine do I really need from what was a good running stock engine ?

Ayuh,..... I donno the mathamagical equation to tell ya exactly, but ya need enough more horsepower to pull another 600/ 800 rpms, draggin' another halfa ton,...

 

[Scott Danforth]

vortec heads are good for about 30-40hp, intake and carb another 10-20. a good cam to make use of it, and you can have about 300 - 330hp at the prop on a 350 easy.

most intakes will not change carb height.

However with your boat at 6500#, I would seriously look into a 383 or 396 stroker kit, especially if you are having the motor built (about $400 extra over a standard build)

 

[Rick Stephens]

However with your boat at 6500#, I would seriously look into a 383 or 396 stroker kit, especially if you are having the motor built (about $400 extra over a standard build)

Wouldn't that much power increase would also require going to a Bravo drive?

 

[Bondo]

Wouldn't that much power increase would also require going to a Bravo drive?

Naw,.... It just requires the Captain to be mindful of what he's doin' with 'is right hand,.....

 

[BearlyFunctioning]

And I am in the habit of finding right where that limit is........