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  #31 (permalink)  
Old 08-08-2006, 08:13 AM
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Just about any Auto engine will work fine in a Marine application, EXCEPT that some marine engines are Reverse Rotation,and a auto engine will not work in place of it. And that alot of auto parts are the exact same as the marine parts, except the marine ones say MARINE on them and cost twice as much
Just make sure you use marine headgaskets and coast gaurd approved electronics, and you should be good to go. Also, use the marine water pump to. Most Marine water pumps will work on either a reverse or standard rotation engine, wear as a auto water pump, will only work on a standard rotation engine. And the Marine water pumps stand up better to corrosion.

If your going for horsepower, be careful if your using a closed cooling system. While they are better for longer lasting engines, they can barely cool a stock 454.


Brad

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  #32 (permalink)  
Old 08-11-2006, 11:07 AM
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I know this thread is related to blocks, but don't the marine engines also use a different cam to get different TQ and HP curves than an auto engine?
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  #33 (permalink)  
Old 08-11-2006, 08:35 PM
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Yes the cams are usually ground to make power below 4500 rpm. Above this rpm, cavitation of the prop/water rears its ugly head.
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  #34 (permalink)  
Old 08-12-2006, 11:28 PM
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there is no real diffrence in the blocks themselves. Some have a specialty coating for the waterpassages to help prevent corrosion. The main diffrence between the two are the carbs and the cams. You can't use a auto carb for a marine engine or you will get a heafty fine from the coast guard, and second is most marine engine from GM are rollers.
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  #35 (permalink)  
Old 08-13-2006, 11:02 AM
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On the carb thing. I "have heard" that the Coast Guard requires a marine carb to injest any fuel that happens to come out the bowl vent in the instance that the float needle sticks open.

In other words, there would be no fuel running out the top of the vent, down the carb, down the engine, and into the bilge water (where it would sit on top) creating either a vapor pool that'll explode or just plain burn the boat to the waterline.
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  #36 (permalink)  
Old 08-13-2006, 07:05 PM
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Down here in Brasil where big blocks are rare,former marine engines is the way to grow up in size.Right now I am adapting a Chevy Volvo Penta 502 Mark V into a '61 Impala.Yes it was quite rusty inside.Even the decks had to be machined to get rid of rust.It is a 4 bolt main unit with forged crank and Rectangular port heads.I am keeping the stock cam - quite big - and stock Holley 850 as well as the stock manifold,in aluminum with a brass sleeve where water flows.Other than that I noticed no other special coating anywhere.
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  #37 (permalink)  
Old 08-17-2006, 08:07 AM
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I have a 455 Olds in my 1971 Sleekcraft jet boat that has "BOAT" dot stamped on the timing cover pad. 4 bolt mains are nice to have, imagine what kind of down force the crankshaft sees when you come crashing down off a wave
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  #38 (permalink)  
Old 08-17-2006, 10:14 AM
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boat motors

Quote:
Originally Posted by Dbodily
Can anyone tell me the differences between a marine block and an auto block. I have a boat that has a 305 gm marine engine. The block has a small crack. I guess I can pull the engine and weld to crack up or I can find another marine block or if there are no real differences just use an auto block. Any info will be appreciated. David
I'VE BUILT HIGH PERFORMANCE BOAT MOTORS FOR YEARS. HERES THE DIFERENCE FROM CAR MOTORS. 1) bronze freeze plugs are required because regular metal ones will rust through. 2) Carberator must have the vent/overflow pipe that is bent back into the carb. You don't want gas in the bilge. These pipes are sold, dont try to bend a stright one. 3) Alternator must be spark free type. Buy a regular marine alternater. Wire the engine in a professional manner and have fun. No other diferences between motors inside.STU
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  #39 (permalink)  
Old 08-19-2006, 07:17 AM
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I work in the service dept of a marina, and the typical Mercruiser/Volvo/etc. marine engine is simply an off the rack Chevy car engine, with the only changes being brass freeze plugs, non=corrosive head gasket, and a slightly different cam profile. There is no special coating in the block, and all of the internal components have GM part numbers stamped all over them that can be crossed right to regular car parts.

The others are also correct that the external components are different. The exhaust manifolds, carbs, fuel pump, starter, alternator and distributor are all coast guard approved and designed to prevent an explosion from gas vapors and sparks.

I have personally put 4 or 5 car/truck engines in my own boats, using the marine components I mentioned above, and they work great. The marine engine manufacturers want you to think there is something special about their long block assemblies so that you come to them for parts, but we buy a lot of our stuff from NAPA. Also, as mentioned, late model marine engines tend to be Vortec roller cam engines, and some even have roller rockers (315 HP)

Hope this helps.


Don
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  #40 (permalink)  
Old 08-20-2006, 11:10 AM
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some info

i helped a friend put a motor in his boat and it was just a normal rebuilt 302 nothing special and it runs great it works just fine in the boat and seems to love the open water. but it does have bronze freeze plugs
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  #41 (permalink)  
Old 08-20-2006, 02:39 PM
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SOME marine engines turn reverse rotation and obviously require a reverse rotation cam and ignition. If they have offset piston pins, then the offset needs to be the other direction. Some have marine specific distributors.

Last edited by xntrik; 08-20-2006 at 02:44 PM.
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  #42 (permalink)  
Old 08-23-2006, 12:59 PM
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Marine engines have the same blocks as auto engines! Except- they have stainless steel or bronze freeze plugs, a higher torque cam, ss valves, marine head gaskets, and roller bearings if newish. Coast Guard approved carb, alt, starter, distrib. and coil, and fuel pump. They can have 2 or 4 bolt mains, nodular or forged cranks and pistons. They can be closed circuit cooled with antifreeze and a heat exchanger or by raw water from the outside of the boat -fresh water or salt water. It is not an even swap to put a car engine into a boat, it does not have the proper torque curve, boats need lots of torque. Its like constantly driving up a BIG hill.

And Merc. is not better than Volvo-Penta or Crusader any others! They all use auto blocks, some manufactures do a better job of marinizing the engines than others.
Lastly the manufactures do keep their specs secret. Try cross referencing a part!
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  #43 (permalink)  
Old 08-23-2006, 05:16 PM
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Do what you want

If you have a motor pod and you arent to concerned about the water getting up into the engine conpartment then you should be just fine, but keep in mind that you are going to have to run a marine cam in the motor to be able to run high rpm for a long time, the marine motors are water tight and are capable of turning R's for long periods
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  #44 (permalink)  
Old 08-23-2006, 09:56 PM
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Quote:
Originally Posted by pillsident
***************is opened for discussions.Fresh article posted on 19.08.2006: [b] ****************its pharmacological action, side Effects and Interactions, usage guide, dose, overdose etc.******************************** board is unofficial medical association. Any information published on this project is for examinational purposes only. In any case be sure to ask your doctor or pharmacist before using any of advice.[/i]
wha...teh...feh? big words there and seems to be nothing to do with the topic in discussion.

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  #45 (permalink)  
Old 09-26-2006, 09:02 AM
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Marine vs Auto

Ford blocks are same for land or water. Check engine rotation, you could need special cam for opposite rotation. As for salt water, I would run isolated system with sea to coolant heat exhanger.
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