Mercruiser 305

Engines, Shafts, Steering, Struts, Rudders, etc.
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Mercruiser 305

Postby fivehorse » Wed Nov 02, 2016 4:18 pm

Does anyone have any thoughts on re-powering a 28' Fisherman with twin 305's? Under-powered? Bad motor? Good motor? Would the transmissions need swapped as well? It seems like most people who choose to swap out go with 350's... curious what y'all think.


-Still looking for my first big M

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Re: Mercruiser 305

Postby honestcharlie56 » Wed Nov 02, 2016 6:40 pm

what currently in the boat now? what shape are they in. Its a whole lot cheaper to rebuild the Chryslers if you have to buy the 305's.
1990 Marinette 32 Sedan Flybridge "Hubba"
Twin Chrysler 318's

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Re: Mercruiser 305

Postby javalin390 » Wed Nov 02, 2016 7:22 pm

The 305's used in the Mercruiser applications had two different ratings, 180HP and 225HP ( 225HP is what Chrysler rated the 318's at) As a kid, Dad had a single 225 I/O in a 28' fiberglass Sea-Ray cabin cruiser w/ flybridge, ran strong, would pull up a skier out of the water and top out around 28 knots. Parts are alot more abundant, but I would tend to agree with Honest Charlie that, it's a lot of the time, cheaper to repower with what the boat came with originally, unless you were able to obtain a set of twin Chevy's with all the accessories still on it, i.e. manifolds, risers, all the raw water plumbing for it, transmissions, etc...Good luck in your search
Jim Elias
1974 37' SedanFlybridge
Twin 360 Chryslers.
Marblehead, Ohio

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Re: Mercruiser 305

Postby fivehorse » Wed Nov 02, 2016 7:35 pm

Sorry, guess I could have been more clear.... there is a 28' Fisherman for sale by me that already has the 305's in it. I was wondering if that should be a red flag to run away or if still worth checking it out? Obviously many other factors to consider but the 305's made me think twice. Thanks for any info!

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Re: Mercruiser 305

Postby EWRice » Wed Nov 02, 2016 9:18 pm

The 305 is not a bad engine. They got a bad name in the automotive world for some reason. They make good torque for their displacement. They tend to be fuel efficient engines. I do know that if you put them side by side with 283/307/327/350 chevys and run them at the top of their rpm range, the 305s will tend to wear out quicker. They share the same stroke as a 350, but have a smaller bore (around 3 3/4" as opposed to 4"). The beauty is, you could always use the external parts of the 305 and install another sbc engine in its place down the road.

It would be cool to have 327 chevys in a Marinette. :mrgreen:
Muskegon Lake
1972 32' Express flybridge
Twin 318s
On board air & prime 920
1963 Thompson Super Sea Lancer
Graymarine 327
1961 Alumacraft 12'
'55 10hp Johnson

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Re: Mercruiser 305

Postby seef158 » Thu Nov 03, 2016 7:36 pm

Eric, I agree on the 327's. I want to repower my 78 28' express with a GM simply for parts availability. I really would like a 327 for some reason even though it isn't period correct. Probably has something to do with a family friend we had when I was growing up, he had a 30' Chris Craft Catalina with twin 327s in it. Riding in that boat got me hooked on this style of boat. I'd still love a wooden boat, but the M is much easier to maintain!
1978 28' express single 318
forest lake, mn
Duluth, mn
Washburn, wi

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Re: Mercruiser 305

Postby Fastjeff » Fri Nov 04, 2016 3:03 pm

The short stroke 327 was always one of my favorite S B Chevies. I have a 305 Mercruiser in my bow rider and, should it need replacement, I'd go with a 350. The two motors are externally similar, and they weight the same, but the 350 has LOTS more power.

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