Register now to get rid of these ads!

Would you use a Marine Block?

Discussion in 'The Hokey Ass Message Board' started by Paul Y, Jan 3, 2009.

  1. Paul Y
    Joined: Dec 29, 2006
    Posts: 633

    Paul Y

    Been offered a good deal on a 4 bolt 454 with forged crank and pistons.

    Only issue is that it was used in an saltwater power boat.

    Would you consider using it bearing in mind the possible corrosion? What sort of check can be done to ensure that the cylinder walls are not thin?

    At the moment it is a bare block std bore etc.

  2. jc555247
    Joined: Jan 1, 2009
    Posts: 29


    I believe marine blocks have a higher nickel content and as such are stronger. How do the heads of the bolts that hold the intake manifold to the block look?
  3. 97
    Joined: May 18, 2005
    Posts: 1,975


    If it is a Mercruiser or other commercially produced marine unit it shouldn't have had saltwater in the block at all, they normally have a heat exchanger which works just like a radiator except that it has the salt water running where a radiator would have air...enclosed in a stainless container of course..... and with it's own separate waterpump. The only part of the engine that usually sees any salt water is the exhaust system from the outlet of the exhaust manifolds ..that's where the heated water goes after it cools the fresh water and glycol mix in the engine/heat exchanger system.

    You can roughly check the wall thickness in a few places with a pair of calipers down through the water holes in the deck .

    I have had problems with a motor that was run using raw salt water cooling.
    I rebuilt the motor and got all the way to putting the heads on and nearly all of the head bolt threads pulled out of the block, helicoiling didn't help either, ... ended up getting a new was in the boat for a long time though...about 7 years.
  4. bobscogin
    Joined: Feb 8, 2007
    Posts: 1,761


    Been down that road. It's out of the boat for a very good reason. I'd look elsewhere.


  5. budd
    Joined: Oct 31, 2006
    Posts: 3,478


    might not be to bad and worth checking out, i have friends with BBC's in boats and they blow them up long before salt could ever do any damage, might be a tall deck and you could build yourself a monster motor.
  6. Had a big olds marine mill in the '70s used it and loved it. But is a crap shoot.
    I got it cheap from a Marina in the Ozarks, came out of an ocean going speed boat like a Scarab or the like. They had replaced two of them when the guy moved inland. Never had a problem with it.

    I guess if you can get in cheap have it sonic tested and its sound you did good, and if its not sound cheap isn't much to loose.
  7. classicfins
    Joined: Dec 16, 2006
    Posts: 592


    I don't mean to hijack this thread, but what is everyone's opinions on running a fresh water engine? I've got a Mercruiser SBC that runs great and has low hours and not sure what's involved in switching it over to run in a vehicle, or if it's even advisable.
  8. Terry O
    Joined: Oct 12, 2004
    Posts: 1,060

    Terry O

    A 454 isn't that hard to come by. I wouldn't start building with a block that has seen salt water when you could spend a couple bucks more and get a non-marine block.
    Check out the "Chevy 409 engines" thread running now for more info.
    I'm a marine surveyor and I've seen some nasty stuff including electrolysis on marine applications.

  9. James427
    Joined: Apr 27, 2008
    Posts: 1,740


    I used a marine Ford 427 without any problems and it had been in the boat since 1968. It had closed cooling though.
  10. Paul Y
    Joined: Dec 29, 2006
    Posts: 633

    Paul Y

    Thanks for the input guys.

    I now have a bit more information on the engine. Engine number is 14015446 which seems to indicate it is a 78-90 BB, non marine.

    The story is that it was removed as the exhaust flap failed and allowed water into the bores, so it will need a rebore to clean up the rust.

    Not seen the engine myself as yet, will get some pictures sent over as a starting point but begining to get cold feet over it.

    The last thing I want to do is spend a lot of money I dont really have on a block that could well be junk.

  11. rq375
    Joined: Sep 23, 2008
    Posts: 103

    from Washington

    if it had water in the bores from a failed exhaust flapper, it probably has bent rods as well; they would not have know it was NFG unless they tried to fire it.
  12. 39 All Ford
    Joined: Sep 15, 2008
    Posts: 1,531

    39 All Ford
    from Benton AR

    IMO boat engines work hard all the time..... You can bet your ass that this core has had a tough life. Combine that with possible salt contamination I would say pass unless you absolutly KNOW that the engine has not had a long difficult life.

    Just think about the last time you were on the water,,,, you would hear a boat just screaming going one direction, then you would hear it just screaming going the other direction.... sometimes for hours on end.... there is no "light use" for performance marine engines...
  13. Cris
    Joined: Jan 3, 2005
    Posts: 808

    from Vermont

    Years ago I remember reading in Car and Driver about a Suburban (this would have been an early 90s one) that GM engineers had built up as a hot rod. They used a Mercruiser marine 454 block as the basis of the supercharged (maybe even twin supercharged?) powerplant. There had to have been inherent pluses to using that block. We've had that exact motor in three or four of our boats and our experience has been that the motors themselves will outlast every single thing they are attached to, regardless of what kind of water is going through them.

  14. temper_mental
    Joined: Oct 22, 2006
    Posts: 2,718

    from Texas

    I looked at marine blocks before I built my motor .All had quality forged parts and had roller valve trains.The part that keep me from going that route was the high compression and the lack of knowing what cam was in the motor and the abuse it had taken.So I spent 8 grand on the block and know what I have your choice BBC are big boy toys
    Last edited: Jan 3, 2009
  15. belair
    Joined: Jul 10, 2006
    Posts: 8,892


    I have a 250 Mercruiser in my 48 fleetline coupe. It was in a lake boat, so no salt. I have had no problems, and got the bonus of a a balanced engine. Your results may vary. Mot marine engines are, as was stated either off or full on. However, they don't see a lot of hours or dogging, so I say that's a wash. I would certainly be leery of a sal water engine.
  16. bobbytnm
    Joined: Dec 16, 2008
    Posts: 1,508


    I might just be blowing smoke here but I think the cams are different aren't they? I think marine engines try to have a long flat HP and torque curve since marine engines are typically run up to a certain rpm and held there whereas car engines are constantly up and down the RPM band.

  17. thewildturkey46
    Joined: Dec 4, 2005
    Posts: 748

    from Rice, MN

    I have a Mercruiser marine 350 SBC in my deuce, has worked fine for over 18K miles. I have been told they are balanced (like Belair said). It was in the car when I bought it, still running strong.
  18. Paul Y
    Joined: Dec 29, 2006
    Posts: 633

    Paul Y

    More details.

    This is just a bare block, crank and rods.

    I have a BBC at the moment that I want to build into a 496 stroker motor with an Eagle crank and rods, so I am really just after the block.

    The idea would be to move the crank and rods on to offset the cost of the block and rebore.

    The more I think about the salt water aspect the more I think I will pass on this. My existing motor is a 2 bolt with a +100 bore, still plenty of life left in them as well.

    There is always a reason why something is cheap...

    Think I might save my money and invest in a set of splayed caps on my existing block.

  19. mitchell stewart
    Joined: Oct 11, 2005
    Posts: 102

    mitchell stewart
    from toronto On

    I have been running a Mercruiser BBC in my p/u for over 30k with no problems. I put in a roller cam,a pair of RHS heads and been driving the nuts of it for 5 years.
  20. Retro Jim
    Joined: May 27, 2007
    Posts: 3,859

    Retro Jim

    I believe you answered your own question when you told us the flap didn't work and ended up with salt water down the cylinders ! FORGET IT !!! You can find good 454 block easily or just buy a new one . Used boat BB have the crap run out of them ! Remember , if the block is still good , then why is it for sale !! My 2 cents !
  21. 97
    Joined: May 18, 2005
    Posts: 1,975


    If it is in the UK I can see why you would look at it...Big Blocks are expensive to ship anywhere outside the USA.
    Sleeves are easy in BBC , and depending on buy price and location it could still be the most economic option in the UK... I bought several complete 454 runners with trans a few months ago for $500 each on the West coast USA. Tall deck 427s can be had for the same money or less.
    If it is in the US and you are looking at importing it and then building the motor, look for something better. I would look at buying a Merlin block and possibly heads from World Products ..maybe even better still check out Ohio Crank and price up a whole short block/long block.... a friend here has been running one of theirs blown on Alky for three years now without a hiccup. Cost him about $4k US

    Watch their specials page good deals appear regularly.
  22. PeteFromTexas
    Joined: Apr 4, 2007
    Posts: 3,837


    If they are better than a regular block then I need to go get a hemi I found that is in a boat!
  23. carcrazyjohn
    Joined: Apr 16, 2008
    Posts: 4,844

    from trevose pa

    marine blocks are stronger 4 bolt i believe casting no are different higher hp check the rotation of the cam some motors cam is reversed id do it
  24. junkyardroad
    Joined: Oct 3, 2007
    Posts: 410

    from Colorado

    I have been running a marine engine for years. Ask that they guarantee that it be rebuildable or money back. I have gotten a couple of nice 540 BBCs used in offshore racing cheap that have no problems.
  25. My 330 horse Crusader marine 454 is only a 2 bolt block.It was used in fresh water and needed freshening up before I stuck it in my 57. Runs great so far!
  26. yoyodyne
    Joined: Nov 26, 2008
    Posts: 855


    What makes a marine engine special? Chevy specifies that their crate motors are "not for marine use". Their 502s for example, which already have 4 bolt mains and good cranks and rods.
  27. mickeyc
    Joined: Jul 8, 2008
    Posts: 1,363


    Hello Paul, here in Louisana gas motors wre used extensively in commercial
    shrimp and crab boats before diesels became affordable. Many of these conversions used standard automobile motors with salt water cooling the
    motor and exhaust manifolds. The more exspensive systems used heat exchanger systems with sea water used for exhaust cooling only. when you say power boat as in a high perfomance type boat that features
    forged motor parts there is a good chance it was freah water cooled. One
    thing of note, never use big block chevy heads that have seen salt water!
    The cooling passages around the valve area have thin castings by design to promote cooling around the combustion chambers. These heads after a few seasons of salt water exposure will absolutely fail, allowing water into the combustion chamber with dire results. MickeyC from the Bayou Country
  28. If the price is right, see if the seller will let you get it boiled out and checked before you buy it. If it checks out ok, you give him the green.


Share This Page

Register now to get rid of these ads!


Copyright © 1995-2021 The Jalopy Journal: Steal our stuff, we'll kick your teeth in. Terms of Service. Privacy Policy.

Atomic Industry
Forum software by XenForo™ ©2010-2014 XenForo Ltd.