Reply With QuoteInternal bearing and surface clearances with respect to thermal dynamics....
what is the differience between a car engine and a boat engine
Internal bearing and surface clearances with respect to thermal dynamics....
Originally posted by boatslayer
what is the differience between a car engine and a boat engine
Slayer,
Why are you asking this question?
LO
I'd kinda like to know too. I've put together a couple street motors and been around them for awhile but boats are a whole nother ballgame.
So bearing clearances are looser, as well as piston-->sidewall. I understand this but why? Boat motors run cooler so I
would think there would be less metal expansion, thus tighter clearances would be OK?
Now tell me why I'm wrong
For example: I have a 454 in a camaro.....what do I have to do to make it survive in a boat aside from the obvious marine accessories?
Its not so much the difference in the engines that you have to worry about, its the way they're used.. Cars coast, boats don't. After you have reached cruising speed in you car, you can feather the gas pedal back and maintain that speed quite easily. In a boat, when you reach cruising speed, you must keep the pedal down to maintain that speed. If you lift, you slow down, right now. Based on this demand, marine type, especially ***boat type engines must be prepared to live through some very extreme demands. As mentioned in the above post, thi$ dictate$ $ome engineering change$, $tronger parts, wider clearance$, and a whole me$$ of expen$ive machine work.. If thi$ was ea$y, think how crowded all the water would be...........Moneypitt
Can somebody provide a list of clearance diffrences on a BBC compared to a car. I want to make sure i know everything thats a bit diffrent. The book i have i'm sure if giving me clearances for car/trucks.
Originally posted by fourspeednup
I'd kinda like to know too. I've put together a couple street motors and been around them for awhile but boats are a whole nother ballgame.
So bearing clearances are looser, as well as piston-->sidewall. I understand this but why? Boat motors run cooler so I
would think there would be less metal expansion, thus tighter clearances would be OK?
Now tell me why I'm wrong
For example: I have a 454 in a camaro.....what do I have to do to make it survive in a boat aside from the obvious marine accessories?
A simpler way of describing it is, the piston expands in demension more due to more heat retention than the block's cold marine bore. The reason the block doesn't want to expand with respect the pistons expansion is mainly because of the coolant, or raw water temp. So in turn you need larger clearances to compensate for this thermal dynamic occurrence. The block often stays cooler in a Marine application then it does an Automobile.
Somebody else also touched up on it a bit as well....we run Marine applications higher in the power band than does an automotive version.
Hope that sheds some light.
~Ty
Mercruiser buys a complete motor from GM, which is the EXACT the same as a car motor, paints it black, bolts on some accessories, puts their decal on it and marks it up 200%+.... Ya... that about covers it.
I have put SEVEN different car motors in boats both with and without thermostats. They are the same...........except for the accessories.
BTW thats why they make thermostats, to compensate for lower operating temps......... understanding the difference in operating temps is important to understand how it will react but does not prevent you from using a car motor in a boat.
Obviously if you can get a motor to run in higher "operating" temp ranges it will perform better. Most unrestricted cooling systems in boats will prevent them from running at the correct operating temps.
MUST have boat accessories include, oil coolers, block drains, correct exhaust (with drains), thermostats, etc.
Originally posted by Hotcrusader76
A simpler way of describing it is, the piston expands in demension more due to more heat retention than the block's cold marine bore. The reason the block doesn't want to expand with respect the pistons expansion is mainly because of the coolant, or raw water temp. So in turn you need larger clearances to compensate for this thermal dynamic occurrence. The block often stays cooler in a Marine application then it does an Automobile.
Somebody else also touched up on it a bit as well....we run Marine applications higher in the power band than does an automotive version.
Hope that sheds some light.
~Ty
Thanks, that's helpful
Are there any books out on this subject that would be worth reading?
thanks for your input guys
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