Inboard Engine and Trans for sale

Boy, I was really out to lunch on the 305 talk. Maybe new glasses are in order. It clearly says 307 and I thought 305.
Had a 307 in my 71 Chevy Blazer, very nice engine, not powerful but ran very smooth and back in the 70's I got 17 MPG in that Blazer with the 307 and a 4 speed.
The 307 is kind of an oddball of parts.
In that period GM was building the 302 for performance cars which used a 283 crankshaft in a 327 block. So the GM 302 was a 4" bore with the 283 crank in it. Short stroke and large bore makes a very high revving engine that made great racing power some revved that 302 Z28 engine to 8,000 plus RPM but it was pretty weak below 3,000 RPM..
The 307 has the 283 bore and used the 327 crankshaft which did the opposite, low rpm grunt but not much high rpm power. Still a good and efficient boat engine with lots more torque than a 283 offered. Should be on track now.

Thank you for the info. This one is an older 307. I looked it up, and it has the same bore as a 283, and the same stroke as a 327. They say it was made for reliable mid range torque (economy). I replaced it with a newer 305 that had electronic ignition and high rise manifolds, along with a few other features I wanted. Once I sort out a couple of minor linkage issues and get a better alignment done, maybe I'll start looking at tweaking the new engine like you indicate.

You must be bored today Keno, the numbers are off. 305 Pistons were 3.7360 not my stated 3.78 but if bored out you get 3.7660 at .030 or 3.7760 at .040 overbore so pretty close to 3.78 bore but the total Cubic Inches are only 334 not 348, I should use the book and not memory as it is proving to not be accurate any longer.
In testing though the little stroked 305 made very good torque, our pIston engineer liked the combo for trucks.
Remember in the 80's the 305 was very common as the standard engine in GM trucks and an upgrade was attractive to those owners and would really help in a boat.

The 305 was a good little engine, just a small version of the 350 using the same 3.5" stroke but smaller pistons. Rather than 4" bore like a 350 it is a 3.78' bore in the 305.

A upgrade you never hear of is to take a 3.75" stroke crankshaft which is usually used to convert a 350 to a 383 and is very popular, cranks are available for around $225 brand new.

Take a 3.75" stroke crank and install it in the 305 and it gives you 348 cubic inches but the layout is more similar to what Oldsmobiles did, smaller pistons and longer stroke.
The 348 conversion is not a race engine but it makes a very nice torque monster out of the 305 engine for not much money.   In testing the 348 out pulled a 350 from 0 to 4,500 RPM.
Above that RPM the 350 had more power but boats live in that 0-4,500 RPM range so this could be a nice combo for someone needing an engine. Just food for thought.
The 305 also used identical parts for a Marine conversion and 350's are available pretty cheap everywhere if someone needs a power unit the parts listed might give you that needed Marine engine.
I had a 305 in a 1986 IROC Z28 and that little thing was fast for that period of time.
The heads that came out in 85 I think gave the stock 305 much better power.
Good luck getting this sold off.

Do you have any pictures you could share? Scott