Difference between marine and auto engines
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Difference between marine and auto engines

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    Default Difference between marine and auto engines

    Ok this is a noobish question but honestly I do not know the answer. I know for a fact the electrical systems (wiring, alternator, starter and such) are different as well as the exhaust manifolds and as far as I can tell often times the cams are different too (higher duration I believe??) as well as the cooling system but beyond on that stuff are they really all that different? For a guy like me with a engine budget measured in hundreds not thousands, what would need to be done to a motor pulled from a car especially the cooling system. I have a very basic understanding of how that all works but putting it into use is another thing. Also the starter is kinda grey to me as well, never had my family's old 1988 Mastercraft down far enough to get a grasp on the difference there either. I am asking this because I am getting alot of interesting offers on project boats here but they all need motors. And I so happen to have a AMC 258 I6, Ford 302, Ford 460 and a Chevy 350 (EFI with electric fuel pump not sure if thats a cause for concern for marine applications or not) sitting around. Some bolt on stuff doesn't scare me at all but I figured I should ask folks who know more than I do about this before I get too gung-ho and get in over my head.

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    Senior Member jimclauss's Avatar
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    Quote Originally Posted by c-dub View Post
    Ok this is a noobish question but honestly I do not know the answer. I know for a fact the electrical systems (wiring, alternator, starter and such) are different as well as the exhaust manifolds and as far as I can tell often times the cams are different too (higher duration I believe??) as well as the cooling system but beyond on that stuff are they really all that different? For a guy like me with a engine budget measured in hundreds not thousands, what would need to be done to a motor pulled from a car especially the cooling system. I have a very basic understanding of how that all works but putting it into use is another thing. Also the starter is kinda grey to me as well, never had my family's old 1988 Mastercraft down far enough to get a grasp on the difference there either. I am asking this because I am getting alot of interesting offers on project boats here but they all need motors. And I so happen to have a AMC 258 I6, Ford 302, Ford 460 and a Chevy 350 (EFI with electric fuel pump not sure if thats a cause for concern for marine applications or not) sitting around. Some bolt on stuff doesn't scare me at all but I figured I should ask folks who know more than I do about this before I get too gung-ho and get in over my head.

    Regards
    Stay with the chevy and junk the rest

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    Quote Originally Posted by jimclauss View Post
    Stay with the chevy and junk the rest
    I get that alot as a 3rd generation Ford guy haha Ford cars and engines have been good to me in racing thus far so I don't see why not to continue using them on the water as i have on land. I don't have any problem with Chevy or their fans but I prefer Ford.

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    Quote Originally Posted by c-dub View Post
    I get that alot as a 3rd generation Ford guy haha Ford cars and engines have been good to me in racing thus far so I don't see why not to continue using them on the water as i have on land. I don't have any problem with Chevy or their fans but I prefer Ford.
    What sort of boat is this going in?

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    Quote Originally Posted by md-11mike View Post
    What sort of boat is this going in?
    Well I dont have a hull yet I am looking at a couple different ones. But what I am looking for is what people in my part of the world call a hot boat, big exposed engine, shoots big ass rooster tails out the back and goes fast to put it as simple as possible. Probably not the answer you was looking for but its not set in stone what the said motor would be going in just yet.

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    Default Auto vs marine

    You've already touched on a few differences, but the one, maybe the biggest one, that you failed to mention is "skirt to wall" clearances.... An automotive engine runs hot compared to most boats. The block expands, as do the pistons, with temperature. In a "open cooling" application you're using the entire body of water as coolant, so the block never sees the sustained temperature needed to expand the block/bores. For this reason, you need to add a few thousandths to the piston skirt to wall clearances because the pistons do get hot and expand..... Many ventures with automotive engines, fresh out of the car/truck, are very quick failures. Additional piston drag plays hell on rod bearings.... Oh, and the oil systems are also quite different.....

    Plainly said, most automotive engines die a quick death in a boat, especially a jetboat. Asking an engine to attempt to compress water is about the toughest thing you can ask an engine to do....AND, boats do not coast...
    Ray
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    Canoe Jockey Michael Thomas's Avatar
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    A chevy engine is the best way to go when you have a thin wallet. When you come up with your hull, just ask some of the guys @ MHB for some stuff..We all have "give away parts" and would be happy to get another boat in our area.
    "If you can't dazzle them with brilliance...Baffle them with bullshit"

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    Senior Member Mash on It's Avatar
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    Quote Originally Posted by Moneypit View Post
    You've already touched on a few differences, but the one, maybe the biggest one, that you failed to mention is "skirt to wall" clearances.... An automotive engine runs hot compared to most boats. The block expands, as do the pistons, with temperature. In a "open cooling" application you're using the entire body of water as coolant, so the block never sees the sustained temperature needed to expand the block/bores. For this reason, you need to add a few thousandths to the piston skirt to wall clearances because the pistons do get hot and expand..... Many ventures with automotive engines, fresh out of the car/truck, are very quick failures. Additional piston drag plays hell on rod bearings.... Oh, and the oil systems are also quite different.....

    Plainly said, most automotive engines die a quick death in a boat, especially a jetboat. Asking an engine to attempt to compress water is about the toughest thing you can ask an engine to do....AND, boats do not coast...
    Ray

    ZZ4 crate motors, not marine,- tunnel jet boats- SEALED motors-40 to 60 minute WOT races, open cooling, How does this work?

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    Quote Originally Posted by c-dub View Post
    Well I dont have a hull yet I am looking at a couple different ones. But what I am looking for is what people in my part of the world call a hot boat, big exposed engine, shoots big ass rooster tails out the back and goes fast to put it as simple as possible. Probably not the answer you was looking for but its not set in stone what the said motor would be going in just yet.
    I also suggest BBC, but it's your $ and your (eventually) boat. Probably 75% of the guys here / and 75% of the boats you will be near on the water have BBC. Therefore, fun parts are abundant and inexpensive - and the guy beached next to you would likely be able to help with any problems that occur on the water. There's like THREE guys here with fast Fords, but that's about it.....

    That being said, piston clearances, as mentioned is one concern - the next is valve guide clearance. Probably the two MAIN differences - but NOT deal killers. Several people here have taken a GM crate motor and shoved it in a boat without any issues. The only real difference to the oil system is usually a bigger pan and associated pickup/screen and windage trays always help since RPM is higher than street use. Pistons for cars are usually set around 3 to 5 thou, whereas boats and car drag motors are usually in the 7 neighborhood. 5 is fine in a boat AS LONG AS YOU GIVE IT SOME BREAK-IN. Same with the guides, usually a bit tighter on car motors. So, as long as a good oil (suggest synthetic of whichever brand you like) is used and you EASE INTO the RPM, you'll be fine. Tighter guides have more friction. Boats spend most of their life at 3000 or more, where are car on the street is usually 3000 or less for 95% of it's life.

    So, for example, If the boat with car motor is driven real easy (below 4000) for 10 hours, with NO WOT RUNS.....then some occasional blips to 4000 and 5000, momentarily, for the next 10 hours, all of the metal/metal parts get to make their homes and mate together for long-term usage. If the tighter guides aren't allowed to do this, the higher RPM right out of the gate causes a bit higher heat, right? The heat expands both the guide(s) and the valve(s). So now those clearances become even tighter. If not allowed to make a home before high-rpm/WOT, valves can start to slow down and "stick". Hot enough, and they become "stuck". All sorts of nastiness starts to happen after that.

    A few here have used, for example, GM ZZ502 crate motors - with zero changes other than oil pan. A similar break-in method was followed by just getting 25 or so hours on the motor before really asking alot of it.
    Last edited by Beer:30; 05-25-2012 at 07:50 AM.
    Quote Originally Posted by gn7 View Post
    EFI is the wave of the future. There can be no denying it. Electronics have been on the leading edge of our entire lives. Not only os the magneto dead, but the standard issue CDI is wavering. Its all about total fuel, air AND spark control. Anybody that thinks its not has their head up their ass.


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    There's like THREE guys here with fast Fords, but that's about it.....

    Boy, is that a bias statement. Do a search for "Ford Motor Pictures".

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    Hah! This is going to turn into a Ford v. Chevy thread

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    I'll be one to go against the grain here...

    Drove my 4x4 over to the place where my boat was parked. Pulled it up against a tree, pulled the engine out(460), swapped a few things off the old boat engine(429) onto the 460 & dropped it into the boat. The things I pulled off the truck engine to get it ready for the boat was the exhaust manifolds, the water pump, alternator, & power steering pump. Also the oil pan & oil pump, had a 10 qt. pan with a rear oil pick up when it was in the truck. Pan was too deep so had to pull the 5 qt. front sump pan & oil pump w/ front oil pick up off the other engine & put it on as well. This engine was not a fresh build, had maybe 9,000-10,000 miles on it by then. I did this as a quick fix to get me by for a boating event & maybe the rest of the summer till I could build something else.

    That was in 2005 & haven't missed a season yet, I'm still running it to this day, lol... Heading to the river for the weekend tomorrow, matter of fact.

    Not saying it would go that way every time, but it is possible. If I personally was picking out of those choices listed, I'd go with the 460 Ford with the 350 Chevy as a second choice, mainly cuz I wouldn't want to screw around with the fuel injection. Good luck with your decision & project.

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    Wow lots of good info here guys thank you. I understand both sides of the battle here, It makes sense why the wall thickness would be issue with how the cooling system is. On the other side of things I feel that a car engine with some modifications would be ok in a boat but with that being said I don't want to shoot myself in the foot by messing up from the start. Going fast would be nice but as long as this boat I am envisioning in my head can outrun the bastard jet-skis that plague Devils Lake I'll be very happy.

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    Quote Originally Posted by c-dub View Post
    Wow lots of good info here guys thank you. I understand both sides of the battle here, It makes sense why the wall thickness would be issue with how the cooling system is. On the other side of things I feel that a car engine with some modifications would be ok in a boat but with that being said I don't want to shoot myself in the foot by messing up from the start. Going fast would be nice but as long as this boat I am envisioning in my head can outrun the bastard jet-skis that plague Devils Lake I'll be very happy.
    c-dub,

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    Last edited by Jet Mad; 05-25-2012 at 11:34 AM.


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