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Swap 350 for 305?

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clarkzkent

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Can I bolt in a 350 Chevy in place of my 305 with no conversions? The existing is a 1978 200D Volvo Penta with 280 sterndrive. Motor block has frozen and broke. Runs good, just fills the engine compartment with water LOL. If a 350 would work, can I use a automobile engine or does it have to be marine? Thanks for your input. Kent
 
Thanks for the post. Do you mean the harmonic balancer? I'm hoping to find a used one from a boatyard. It should have the balancer and fly wheel? I'm also wondering if I need to change the prop. I'm assuming a 350 would have more power.
 
Depending on the year of the 5.7L, most all parts will transfer over.
Be sure to adjust the side engine mount elevation so that there is no excessive out-of-alignment torque on the flywheel cover.

With no known camshaft specs, I can only advise you as that excessive over-lap may lead to water reversion.

Since you mentioned that the 5.0L engine block had cracked, this is likely a raw water cooling system. The automotive head gaskets will potentially fail early if used in a RWC scenario.
The casting core plugs (if not changed to brass) will also fail early.

Between the early 2 pc rear main seal, and the post '87 1 pc rear main seal, the flywheels are not the same.
The flywheel must be the smaller 153 tooth (the 168 tooth will not fit within the flywheel cover).

The drive ratio for a single prop drive will be the same...... 1.61:1.

I'd wait to see if you can reach your WOT RPM range before experimenting with props.




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clarkzkent said:
Probably have more questions once I find an engine.
Click to expand...
Ah.... I assumed that you had found an automotive SBC.
Since you have not, keep your search limited to a SBC with the correct compression ratio, correct camshaft profile, and more importantly, steer clear of any with the full dished pistions............. and especially if this hull is anything around 24 feet or larger.

Marine loads are quite different from that of automotive.
Short of over-heating and/or low oil pressure......... Detonation is one of our worst enemies.
The full dished pistons do ZERO to limit detonation.
They are used commonly, but should actually NEVER be used in the true Marine version SBC. :mad:



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I'm about 22 feet, 1978 Bayliner Skagitt. I have come to the firm conclusion that another 305 marine is going back in. Would you recommend welding the cast iron engine block? It runs great. Just fills the engine compartment with water. The crack is about 4 inches long running parallel with the head about 3/4 inch down. It has pushed out a little more than 1/2 inch. The other side shows cracks but didn't rupture yet. Just wondering if you had experienced a welded block and if it could be reliable. Lots of posts online showing how. No one ever says anything about it lasting or not. Thanks again for your input.
 
clarkzkent said:
I'm about 22 feet, 1978 Bayliner Skagitt. I have come to the firm conclusion that another 305 marine is going back in. Would you recommend welding the cast iron engine block? It runs great. Just fills the engine compartment with water. The crack is about 4 inches long running parallel with the head about 3/4 inch down. It has pushed out a little more than 1/2 inch. The other side shows cracks but didn't rupture yet. Just wondering if you had experienced a welded block and if it could be reliable. Lots of posts online showing how. No one ever says anything about it lasting or not. Thanks again for your input.
Click to expand...

I used JB Weld on a 305 ci block in similar condition. It worked great and did not leak. Out lasted the engine.
 
I also used JB on a cracked block. Grind or wire brush the area until it's shiny, push the JB into the crack and slather an eight of an inch or so over the whole area. What have you got to lose? If it still leaks, put some more on.
 
I appreciate the input. Did some research and found a product from Belzona for fixing engine blocks, etc... Expensive compared to JB Weld, but they actually use it in Cat engines in the compression area and it works. Like you said, what do I have to lose.
 
You can trust Belzona products, they are meant for professional use and they are widely use on large freighters. Just make sure you pick the right one. :)
 
Thanks for the support. I am amazed at this product. I had called Marine Tec as recommended in another thread, but they do not recommend using their product. When I called Belzona, they recommended the 1111 for my application and gave me thorough instructions on using it. Anxiously awaiting the arrival so I can get it fixed and back in the water. I will post when finished and tested.
 
Finally able to complete this project and test it. Happy to say it seems to be holding well. Only an hour of run time so far, but I expect this to last the life time of the engine. Followed the manufacturers recommendations and included photos. Cleaned area, stop drilled cracks, bevel ground cracks, light grinding of entire area, cooked oil and water out of area with torch, triple cleaned with acetone just before application of product. The key to the side that opened up was the "strap" fabrication attached by drilling and tapping. All of these preparations were included in the Belzona literature. Thanks for the suggestions and help from the bloggers. (Tried to attach photos, but not working? Sorry)
 
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