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Random Quote: Work only gets in the way of fishing
I have a 305 Chevy in my old Chris. Am I understanding correctly that most of the stuff on this engine, etc. intake, pulley's and so forth will fit on a short/long block 350. If so then a re-power job would be much less than a complete new engine.
Yes, the block and heads are the same casting. They just have different internal machine work. Everything will bolt up and a 350 is usually cheaper than a 305. I would just get a long block unless your manifolds need replaceing. Assumeing your peripherals are ok, you can get a local automotive rebuilder to sell you a long block with the marine grind camshaft since it is the only thing different between an auto long block and a marine long block. Don't use an automotive camshaft or you could suck water into the cylinders.
Dimensionally they are both the same. The only difference between a 350 and 305 is the bore, a 350 has a 4" bore and a 305 has a 3.750 bore. They normally use different heads and cams as well since the 350 flows more air than a 305, but they can be interchanged for a budget swap. You would probably need to up your jetting a size or 2 if your engine is carb'd, if it is injected you'll have to get www.azspeed-marine.com to re-map your ECM to match the increased displacement and fuel demands.
There is no difference in these engines on the outside except maybe for the harmonic balancer, I can't remember. Buy a remanufactered long block assembly and let the swap begin. The heads on the 305 and 350 are different internally. Also, a marine engine has stainless head gaskets and brass freeze plugs and the cam makes maximum torque at about 3000 rpm's.
As has been stated the bore is the difference both use the same crank and other parts If you got a short block all the pullys and brackets would be a perfect fit
I beg to differ but that's outdated BS......the days of the marine engines being pulled off the truck duty lines is long gone. The only difference is as follows: stainless head gaskets, brass freeze plugs, marine cam(late 1960's Z28 camaro grind), marine circulating pump and ignition protected electrical components.
There is a big difference between boat engines and car/truck engines! One other thing is that car and truck engines sometimes have higher compression and need premium fuel, which you can't find at marinas. If you don’t use the right fuel you are very likely to burn valves or worse. Go with the right stuff the first time for your boat or you will regret it later! Cheap boat parts are like cheap paint-no such thing!
Never forget that you can't pull over to the side of the ocean when you break down!
GM's latest generation of marine engines are slightly more marinized with stainless steel valves and hardend exhaust valve seat inserts. But, except for the newest of the new, marine engines and auotmotive engines from GM are internally identical short of the head gaskets and freeze plugs.
I just put a 98 350 into a SEARAY I'm redoing, the casting numbers and everything are the same as the truck versions. It does have stainless valves and a different camshaft in it with a MERCRUISER intake though. But this is not true for all of them. My 98 is a VORTEC design with different internals than the old school engines had. Many of the old blocks had different metal contents to them to slow down corrosion and rot from salt water and make the blocks more rigid. You can get a small block casting number book to confirm what is what.
Some of the late 60's, early 70's blocks were high nickel/high tin blocks. The casting number was 3970010, but not all of that number were the high nickel/high tin blocks. Not all were even 4-bolt mains. Some high nickel/high tin blocks were cast as 2-bolt main blocks as well. The nickel added some strength. The tin aided in molten iron filling out the mold better to provide a more consistent casting. Neither added corrosion resistance. About the only difference between a marine block and an automotive is that most marine blocks were 4-bolt mains. On the automotive side, it went either way. Many trucks had 4-bolts, many did not. The same was true of cars, but fewer cars had 4-bolt blocks. All of the new Gen I blocks GM is turning out today are 4-bolt blocks.
GM simply does not produce a "marine engine block assembly". All 305/350's are the same block/crank/rods/pistons as their street counterparts. Listen to gopher and GMC, everything else is indeed BS. Quite frankly, if you have a fresh water cooled (closed system) on your boat, ANY 350 will work..you don't even need the stainless head gaskets. Now, some early Chris Crafts used counter rotating engines..if this is your case, you pay extra for a counter-rotating engine. Consider swapping out the prop and starter and the distributor gear, and swapping the rotation of the tranny to use a standard rotation engine. Standard engines are preferred because of piston pin offset and cam end thrust.
I have a 305 Chevy in my old Chris. Am I understanding correctly that most of the stuff on this engine, etc. intake, pulley's and so forth will fit on a short/long block 350. If so then a re-power job would be much less than a complete new engine.
Thanks for the input.
I repowered an old Chris-Craft straight inboard twice. I went to the 350 ci block. Mine had a right hand rotation engine and the shaft was offset from the cl of the hull to compensate for it. You could not use a standard rotation engine on that boat. Find out if this is applicable to your boat.
I would forget the short/long block idea unless the engine you are replacing is only a couple of years old and you know its service history. All the accessory stuff wears out and corrodes too. If its time to replace the block its time to replace everything. I used complete new marine inboard engines from Marine Power the first time and Crusader the second time. If I was doing it today I would get another Crusader.
Thanks guys. At least for the time being I know I can use some of the left over 350 stuff I have from my last boat. Most likely in the overall scheme of things a new engine is the better way to go if you are going to keep the boat.
Yea GMC, all ya gotta do is turn the piston 180 degrees. In racing, sometimes we'd reverse the pistons, the theory being the pin offset allows less rod angle on the power stroke, and the engine should make more power. Lotsa forged buckets are zero offset. It's all about noise.
305 Chevy vs. 350 Chevy 
