4 barrel carb on '1977 Mercruiser 165

[Glassparman]

OK, forgive me if this is a stupid question, I just don't know the answer.

I picked up a 1977 26' Fiberform with twin Mercruiser 165's that have less than 200 hrs and were covered up by an upper deck their whole life.

As I'm stripping down the engine for cleanup, I notice that it has a 2 bbl carb but after removal, it looks like the manifold was designed to take a 4 bbl carb.

Any knowledge in this area? Was a 4 bbl an option?

Second question:

This boat had twins . . . I'm going to use just one engine/outdrive in my '62 Glasspar Ventura that is a 21' cabin cruiser. Do you think I would need to change any gearing in the outdrive? I'm new to the I/O world so I really don't know the answer.

thanks in advance,
Michael

 

[zbnutcase]

Re: 4 barrel carb on '1977 Mercruiser 165

Yes a 4bbl was used on the 200hp 292 inline six Mercruiser a rare bird today (never seen one in 24yrs of wrenching on boats), same manifold used on the 250 165hp with 2bbl adapter.

 

[Kainon]

Re: 4 barrel carb on '1977 Mercruiser 165

I've played with putting a 4bbl Rochester and Webber style on my 165, and what I found was that I beleive you need to have the restrictor in place that's under the 2bbl adapter as it effects operation in all ranges especially from 3000rpm + ( mine fell flat 3300 ), I made a 1" alum spacer plate to go under the carb, and intend to attach the restrictor with some home made brackets maybe attaching with JB Weld. I also have a place for the throttle arm to attach to the plate.

As for the right outdrive to use, you want the 1.65R drives that came with the engines ( if any), and I would probably hold onto everything to have as spare. the 1.98R Drives are for 4 Cylinder 120/140's the Mercruiser 470/170/180's use the 1.65, the 4.3L V6 uses 1.84R and 305/350ci 260hp+ engines use 1.50r drives (not sure on the big blocks)

You should have 19p Props, maybe 21p, depending on the hull design and condition of the engines I would try what you have and go from there, noting the WOT RPM. the inline 6 likes 3800-4200.