'57 Chris Craft restoration nearing completion, but...

Gas isn't a problem. You just need to do it right and follow ABYC guidelines. When I upgraded my ventilation system years ago I installed two engine room ventilation fans. A primary and a backup. Just the other day I was working on removing the prop shaft from the v-drive. The coupling bolts have Loctite on them and were hard to get moving. Not much room to work. I didn't smell anything (I never do) but turned on the fans anyway. Got in there with a propane torch, carefully, and warmed up the bolts. I was only three feet away from my fuel tanks with a lot of gasoline in them.

Remember the original poster is trying to do a reasonably economical repower. I look at it this way. For larger boats, especially ones that travel long distances diesel is great. This guy has a 28'. He's not crossing oceans and he's already set up for gas. Let's help him set up his gas engines, that's what he asked us to do.

MIA

 

I'll let you advise on the gas setup. I think gas on boats is dangerous. We had a gas powered boat blow up couple years back at marina I was working on my boats in. Burned up three neighboring boats as well, all in the water, and seriously injured, serious burned the two men on the gas boat, jumped or blown into water..
I wouldn't own one for free.
I have heard people claim they can extinguish a ligted cogarette in a bucket of gasoline. Not anywhere near my boats, they won't!

 

Hercules are great industrial/marine engines and will have a much longer service life than any automotive conversion. If you are looking for the most economic solution, rebuilding the existing engines is the best. Parts are readily available for them.

 

Afraid that could be misinterpreted; the oil pump rotation depends on input shaft rotation in order to pressurize the right components. The 72C version is designed to have forward output direction same as input; ie handed propellers require the engines to be handed as well, one left and one right rotating. The 71C version is designed for "normal", right hand input rotation, and can work with either right or left output rotation. But its fwd and reverse ratios are not identical, so handed props will have slightly different pitch to suit the required operating point. IE: do not rotate the oil pump in a 71C!

 

Most larger horsepower outboards are available in counter rotating configurations.
\Oops already covered

 

Starter and Alternator, marine style, flame arrested
Carburetor, depending on the type, float vented to the throat of the carb between the intake and flame arrestor
Distributor flame arrested as well
You might find as another contributor suggested a complete drop in package from the many places that marinize engines not far off the price of doing the rebuild yourself as purchasing aftermarket water cooled and exhausts can be an expensive event.
Redline, Kodiak/Kem, even Mercruiser have available aftermarket engines. Also many of the marinizers offer remans but new bolt ons and often may come with transmissions and vdrives at a much cheaper cost than buying these
from a normal marine supply dealer. The marinizers buy blocks and components at OEM pricing which can run 40% of what you will pay retail.

Most of the marinizers utilize EFI though some still offer a carb set up.

You mentioned 283, the 350 should be close to the same weight, parts easier available,

 

The 283 and 350 have been out of production for many years. The 5.7 is a better engine and much lighter.

 

Correct, I should have said 5.7 but the 5.7 and the 350 are the same displacement without cutting hairs, are similar in basic 3.90 inch bore and 3.62 inches of stroke. The 5.7 is lighter and the changes to the Vortec configuration gave it more horsepower.

 

Can you change the rotation of a velvet drive? https://www.boatdesign.net/threads/can-you-change-the-rotation-of-a-velvet-drive.51269/
yes you do rotate the pump in a 71C if you want it to turn the other way.
I have had one of my 72c apart for a rebuild and the pump is marked.

 

Yes, if you want to change the INPUT rotation, but NOT for switching fwd/reverse direction with standard right hand input rotation.

 

I NEVER said you could do that. The trans can be setup to turn either way, and you assumed something else like using a left turn motor to spin a right turn prop, then you said the 71c is different about this than the 72 and it is not. I dont expect you will ever understand yourself what you wrote. The diff between 71 and 72 series is torque and horsepower, not directional rotation differences.

 

Just a point of reference. The 283 small black has indeed been out of production for a long time. However you can still buy the classic 350 CID small block engines (these are crate engines made by GM). GM hasn't actually used the 5.7 liter or 350 engine since 2003 when they went to the 5.3's and 6.0 liter engines. Of course parts availability of the 350, in almost all of it's various incarnations is vast from GM directly or in the aftermarket.

General Motors Introduces New 350 V8 Service Engine https://gmauthority.com/blog/2020/07/general-motors-introduces-new-350-v8-service-engine/

BTW, I looked at some specs on those Hercules engines. Calling them robust would really be an understatement. If you can still get parts I can see why you'd recommend a rebuild.

 

The 5.7 GM is still in production for marine applications. Search online, there are many companies selling them.

 

This is a great reply. It is so much easier to fix what is already in the hole. Every time I have changed to different engines it has been a major pia.

 

Thanks for all of the insight. very valuable.
Now I will focus on researching parts to rebuild my straight 6's. I am attaching pics of the boat, as purchased, since currently I have a million projects going on simultaneously and not one of them complete to take better pics!)