1995 GM 305 Merc 5.0 v8 190 HP :(

[jeepnsam]

2 barrel merc carb only puts out 190 HP so i'm thinking about putting in a 4 barrel to get 220 HP.
Anyone ever done a conversion? Is there a kit that can be purchased for the DIYer? then
have a real marine shop dial it in with a lake test??

 

[rod_stewart]

I had a 198 hp 305 Merc at one time and thought about doing the same thing, but never did.
I often wondered why Merc ever offered a 2 bbl 305, when a 4 bbl 4.3 V-6 will put out the same power, with considerably less weight.
My approach would be to see if you can locate a 305 or 350 intake manifold and Q'jet carb from a marine bone yard.
This should make the cost reasonable and all you would need is a carb rebuild.

Rod

 

[kghost]

One more piece of the equation,

When mercury offered there higher output motors, Example 260 hp 350 vs the 280 hp 350, only difference was intake (slightly higher profile), flame arrestor ~4" tall vs 2" tall. I also belive they recalibrated the secondary hanger and needles that hung on the hanger to a slightly richer configuration (on the rochester quadrajet)

I did a part for part comparison on this issue once a long while ago.

That being said, 20 hp gain on a boat is almost insignificant, cost vs gain is not worth the effort.

I also dont believe there is 30 hp with a carb and manifold change on a 305 ci motor. That is a bit of a strech, Possible but unlikely.

The 305 is not a perfomance based motor, If it were a 350 then a cam, intake and carb change could get you 50 + hp gains.......

JMHO.......