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Need engine info Please.

Old 07-23-2009, 05:08 AM
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Default Need engine info Please.

For many years people coment that marine engines are similar to regular car engines and can be used in a boat,basicaly its the same,but others say that marine engines have some special treatment for salt water corrotion.I want to ask mariners that have been in this bussiness for a long time how true its this,do i need a heat exchange divise or can it be done or its pure ignorance from back yard mechanics,,I recently recieved a 28 ft sports fisher seabird boat for free and its in fair condition but the engines are in bad shape,it has twin 360 Chrysler engines,and so far in this site every one who knows about this boats regards them as great performanse boats.Any info will help me dicide if i will dercard them or rebuild them.Thank you.joe
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Old 07-23-2009, 05:21 AM
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Welcome Joe you may get more help up in the boating forum with this question

Last edited by TimW Texas; 07-24-2009 at 03:55 AM.
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Old 07-23-2009, 05:31 AM
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Hi Joe and welcome to the site.

I can not comment on all things you've asked but I believe there is much to be gained in rebuilding the engines you have over buying replacement engines. Chances are the replacement engines will have time on them, whereas if you rebuild you are starting with zero hours. Rebuilding the engines you have gives you the opportunity to modify them to give you better performance and better fuel economy. You've started off at zero dollars so spending a few thou will not be the end of the world....I'd rebuild.

I am a I/O owner as well. I believe the engines are basically the same as automotive engines. Yes the ignition system has differences but they are fundamentally the same, but not all out replaceable. The exhaust is different, but interchangeable. A marine engine uses a different air filter than it's counter part in the automotive industry - do not use an automotive air filter in the marine environment.
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Old 07-23-2009, 07:30 PM
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So... what do you want to know? LOL
We've taken stock blocks (take your pick) and proped them on a CNC. The stock machining is so far off it makes you wonder how they have run so long. A PROPERLY rebuilt engine is superior to assembly line jobs any day of the week. The small MOPARs you have in your boat are a fantastic base to build upon, and about as bulletproof as they can be.

To keep the corrosion away, just flush the engines with fresh water when you haul the boat or get to dock. Over time the salt WILL eat away at the block, there's nothing you can do, but you can slow the process.

The biggest issue I've seen with a marine engine is running piston to wall clearance too tight. Now I'm all about building an engine tight, but since the temperature of the water in the jackets is very cool compared to an automotive engine (due to ambient water pickup) the cylinder doesn't grow with the piston as the piston gets hot. Running to tight can scuff the slug and destroy the rings' ability to seal. In extreme cases, it may even seize.
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Old 07-23-2009, 08:01 PM
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Same motor but different goodies.............

Alternator is sealed not open like a car
Starter is sealed
Freeze plugs are Diff.
As said above , the rings may be diff.
Spark arresto on carbed motors
Heat exchanger instead of radiator
Raw water Exhaust manifolds
Tinned wiring
Better corrosion paint on motor

And a few more things but the BIG difference is the SPARK problem around the motor as the motors are enclosed and may have gas fumes around them of which could make for a VERY bad day.

Good luck with your rebuild .
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Old 07-24-2009, 04:45 AM
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To add to Welder, mechanical fuel pump is marine rated - has sealed bowl on bottom to catch fuel should the diaphram rupture and tubing to "drain" the bowl up to the carb.

The statement that marine engines are modified automotive/truck engines is basically true. The blocks are the same, but as stated, there can be some relatively minor internal differences. As Welder pointed out, most of the differences relate to the bolt-ons.

Regarding the heat exchanger - the answer is it depends. The heat exchanger system predominate benefit is to prevent internal engine and possibly internal exhaust manifold and exhaust riser corrosion (all depends upon how system is routed) If boat is used in fresh water, there is only a small benefit from having the heat exchanger. If boat is to be used in salt water, the heat exchanger is a very good idea. Some salt water ski boats do not use a heat exchanger because it adds additional weight to the engine/boat. Sometimes engine compartment space also plays into the equation.

The terminology related to the heat exchanger is raw water cooled - no heat exchanger; or fresh water cooled - heat exchanger. Raw water cooled implies that the engine block is cooled by running the water the boat operates in through the block, typically with a thermostat rated at abt 20 degrees lower than its fresh water cooled equivalent. Fresh water cooled implies that antifreeze is pumped through the block, and the heat is transferred out of the antifreeze with the heat exchanger. Think of the heat exchanger as a radiator that uses water instead of air to cool the antifreeze.

Last edited by chrisjb; 07-24-2009 at 04:57 AM.
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Old 07-27-2009, 06:11 PM
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Originally Posted by chrisjb View Post
To add to Welder, mechanical fuel pump is marine rated - has sealed bowl on bottom to catch fuel should the diaphram rupture and tubing to "drain" the bowl up to the carb.

The statement that marine engines are modified automotive/truck engines is basically true. The blocks are the same, but as stated, there can be some relatively minor internal differences. As Welder pointed out, most of the differences relate to the bolt-ons.

Regarding the heat exchanger - the answer is it depends. The heat exchanger system predominate benefit is to prevent internal engine and possibly internal exhaust manifold and exhaust riser corrosion (all depends upon how system is routed) If boat is used in fresh water, there is only a small benefit from having the heat exchanger. If boat is to be used in salt water, the heat exchanger is a very good idea. Some salt water ski boats do not use a heat exchanger because it adds additional weight to the engine/boat. Sometimes engine compartment space also plays into the equation.

The terminology related to the heat exchanger is raw water cooled - no heat exchanger; or fresh water cooled - heat exchanger. Raw water cooled implies that the engine block is cooled by running the water the boat operates in through the block, typically with a thermostat rated at abt 20 degrees lower than its fresh water cooled equivalent. Fresh water cooled implies that antifreeze is pumped through the block, and the heat is transferred out of the antifreeze with the heat exchanger. Think of the heat exchanger as a radiator that uses water instead of air to cool the antifreeze.
Originally Posted by TimW Texas View Post
Welcome Joe you may get more help up in the boating forum with this question
Thank you guys,i am a little lost,just joined this great site and still lerning the rules and the best way to utilize the site better,but so far the people that had coment on this ,has been a great help in this new projet,thank you again,,joe
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Old 07-27-2009, 06:19 PM
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Default Need engine info reply.

Thank you guys,i am a little lost,just joined this great site and still lerning the rules and the best way to utilize the site better,but so far the people that had coment on this ,has been a great help in this new projet,iI will take note of all the advises,,thank you again,,joe
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