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Technical Are Marine Motors worth screwing with?

Discussion in 'The Hokey Ass Message Board' started by Crazy Steve, Jun 23, 2020.

  1. I'm sure this has come up before somewhere, but has anybody have experiences with salvaging marinized engines for cars? Repower take-outs can be had pretty cheap sometimes and some feature better performance parts as standard compared to their automotive cousins. I salvaged a late 302 a number of years ago and it had the 'good' D0 351 heads on it with screw-in studs and guideplates from the factory, plus a few other interesting goodies like a three-bolt 50 oz damper. Unfortunately, the block was cracked....

    My main concern would be rust if it had a 'open' cooling system and around here that likely means salt water cooled. Had bad does the rust have to get before it's beyond the point of saving? What's the best method of cleaning one out?
  2. Jmountainjr
    Joined: Dec 29, 2006
    Posts: 1,221


    Yes, raw water cooled engines have the potential to have thin cylinder walls. More so in salt water. But not always. About all you can do it buy it right, have it hot tanked, and after it clean have the cylinders thickness tested. I would look for a heat exchanger cooled engine.
  3. oldiron 440
    Joined: Dec 12, 2018
    Posts: 1,509

    oldiron 440

    You need to be aware that some are reverse rotation in twin aplacations.
  4. Yeah, reverse rotation is pretty common even in single applications but that's easily fixed.
    mgtstumpy likes this.

  5. H380
    Joined: Sep 20, 2015
    Posts: 445

    from Louisiana

    100% if you live by the coast and saltwater pass on raw water cooled mercruisers. I wood only look at engines with "from the factory" heat exchangers. Also cheap skates will overhaul a marine engine and use the cheapest Chinese ebay automotive gasket set possible. Then the head gasket goes and you have salt water in the cylinders. Let the boat sit in the back yard 3 or 4 years. Then put it up for sale "running when last used".

    Honestly you can't get rid of the salt. It always comes back. Had a friend in the 80's rebuild a raw water 454 from a shrimp skiff that blew a head gasket. He had it tanked twice and a Mercruiser dealer did the rebuild with new heads. He installed a heat exchanger. The block put out so much rust scale it plugged the exchanger 2 times the first season. He had to pull the thermostat twice a week to clean the crap out and ended up taking it out. The second season it made a chunk of scale large enough to plug up a port in one head and blow a head gasket. The flakes were up to the size and thickness of a penny.
    Truck64 likes this.
  6. blowby
    Joined: Dec 27, 2012
    Posts: 6,865

    from Nicasio Ca

    I would think some are

    tractorguy, egads and Hnstray like this.
  7. 210superair
    Joined: Jun 23, 2020
    Posts: 183


    I'm a boat guy, and have played with some pretty cool engines. I agree with skipping anything that's been in salt water, 100%. Closed cooling systems are pretty rare in anything that's not pretty new.

    I've got this cool Chris Craft Hercules MBL tri-carb to rebuild right now. Not something to drop in a car, but these herc str8 6's sound amazing. Sneak Pic of the boat too... 20200611_171014.jpg 20200611_170945.jpg 20200613_154108.jpg
  8. southcross2631
    Joined: Jan 20, 2013
    Posts: 3,997


    I picked up a 454 block from an off shore boat in Ga. I had it hot tanked and sonic tested. It took a .060 over bore with no issues. I put a set of 12 to 1 pistons and put over 500 passes on it and then sold it to another racer who ran it 2 more seasons in Super Pro and Super Gas in his Chevy 2.
    The oval port heads also came from a boat. I paid 50 bucks for the block and 50 for the heads.
    I have seen salt water big blocks with rust holes in the bores and in the combustion chamber.
    Our marine patrol training boats were always getting new power plants due to corrosion.
    210superair likes this.
  9. woodiewagon46
    Joined: Mar 14, 2013
    Posts: 1,712

    from New York

    Not if it's a saltwater engine. I don't think that there is an engine rebuilder on Long Island that will touch a cast iron engine that has it's inside eaten away with salt water. Have you ever seen the insides of an engine cooled by saltwater?
    210superair likes this.
  10. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,973


    No experence with boats But isn't a heat exchanger cheaper than wet exhaust.
  11. miker98038
    Joined: Jan 24, 2011
    Posts: 486


    Kind of depends where you come from. You're not that far from me. A lot of the ski boats mainly see fresh water in the lakes. Run hard, but fresh water. Only if you know the history.

    I grew up on boats, and Dad was real careful to idle in slowly in salt water, and cool everything down. We normally moored in Lake Washington, so they got a good rinse after coming back thru the locks. Same with "fresh water cooled" with a heat exchanger. Since the engine ran with a pressure cap, the minute you lost coolant you looked for a bad heat exchanger as it was leaking the salt side into the engine side.

    But it's a crap shoot unless you know the history.

    All the engines had "wet" exhaust, heat exchanger or not. Had to keep the pipes cool to exit thru the transom. We never had anything with exhaust out the top.
  12. Beanscoot
    Joined: May 14, 2008
    Posts: 1,587


    I once brought a rejected 351W salt water cooled block from the machine shop I worked at to a local community college as a practice block. They skimmed the decks nice and shiny, but the next day the deck surface had numerous little rust patches sprouting.

    It appears to be evidence that cast iron truly is a bit porous and will absorb the salt water right into the metal.
  13. Remember marine cams are different from street cams.

    Charlie Stephens
    210superair likes this.
  14. Beanscoot
    Joined: May 14, 2008
    Posts: 1,587


    Back in the '80s it was commonly stated that the small block Ford HO engine used the "marine cam".
    I have no idea if it was true, or marketing mumbo jumbo.
  15. Deuces
    Joined: Nov 3, 2009
    Posts: 18,706

    from Michigan

    I have a new one that I pulled out of a B-58 Windsor short block.... I went with an X-303 roller cam instead.....
    lothiandon1940 likes this.
  16. sunbeam
    Joined: Oct 22, 2010
    Posts: 4,973


    Unless they are reverse rotation they are ground for low end torque A prop is always grabbing not like a loose converter or spinning the tires to get it in it's RPM range. If you have a standard trans car with a big cam try letting the clutch out at an idle in high gear and standing on it and see how fast it is.
    Last edited: Jun 24, 2020
  17. mickeyc
    Joined: Jul 8, 2008
    Posts: 1,075


    Here in Louisiana a lot of shrimpers used
    big block Chevy motors in shrimp skiffs.
    The ones that used sea water to cool the
    motor almost always had a rust out around
    the intake or exhaust valve in the combustion chamber. I was out with a buddy
    in his skiff one afternoon when the cadence of the motor suddenly changed its tone. A few moments later it sputtered and died. The
    motor was locked up solid. When we pulled it down one cylinder was loaded with water. I
    thought it had blown a head gasket. A mechanic shrimper told us to look at the heads closely. Upon examination a small
    dark spot was spotted at the edge of the
    valve seat. When probed with a screwdriver
    I was able to push the tool completely into
    the head opening up a hole as large as a dime. Heat exchanged motors seldom had
    such issues. I used 455 Olds motors in my
    skiff also salt water cooled. The Olds must
    have had heavier castings. I never had any
    internal rust issues. Now most shrimpers
    run diesels for the obvious advantages of
    torque, longevity and such. Not to mention
    the clandestine advantage of trading a basket
    of fresh caught shrimp for a charge of diesel
    fuel to a passing tug or crew boat. Most shrimp guys carry a 12 volt high volume
    fuel pump and a long section of transfer hose for just such encounters! Life on the
    Louisiana bayou can be quite eventful at times.
  18. belair_54
    Joined: Aug 17, 2010
    Posts: 73

    from australia

    My brother bought a 350 chevy out of a ski boat for his 68 chevelle we proceded to rebuild it bored it 60 thou over after running it for less than 30 mins coolant seeped through a fine crack in one of the cylinders caused by corroded water jackets during its previous life.
    That was our initiation to stay away from boat engines. What made it worse we ended up finding a beautiful virgin block that had water jackets that looked like they were brand new my brother ended up re-boring that block 60 thou over to fit the parts from his previous engine.
    Also another point boat engines live a rough life and always under maximum load that means everything in the motor would have been stressed so if you are going to rebuild i would replace all fasteners as well as other parts
  19. alanp561
    Joined: Oct 1, 2017
    Posts: 1,181


    Couple of years ago when scrap steel was going for 3 cents a pound, I was in a scrap yard in Chattanooga unloading and a guy pulled in next to me with eight 454 marine engines, some with the outdrives still attached. I questioned him about where they came from. He said they were all local engines from work boats on the Tennessee river. I could have bought the whole lot for 10 cents a pound. There had to be a lot of usable parts in that group. I just didn't need 8 Chevy motors cluttering up my place. Had they been Fords, the story might have been different;)
  20. alphabet soup
    Joined: Jan 8, 2011
    Posts: 1,418

    alphabet soup

    I put a reverse rotation 426 Mopar short block in my '40, first time around. Had a rear main oil leak. Turns out the seal journal also had reverse knurling. It was helping push the oil out. Polished the knurling off. Stayed a little wet at the seal area, but didn't leak. Don't know if all manufacturers do this, but seen it on a couple of Chrysler cranks. Gene.
    lothiandon1940 and alanp561 like this.
  21. BamaMav
    Joined: Jun 19, 2011
    Posts: 4,421

    from Berry, AL

    What about the 4cyl Mercruiser engines some guys like to run in their A's? Do they suffer as bad as the V8's from rust, or is it less due to it just being a smaller engine?

    Interesting thread, bringing up things I haven't thought about....
    tractorguy likes this.
  22. brigrat
    Joined: Nov 9, 2007
    Posts: 5,272

    from Wa.St.

    Some rebuilders won't take a marine block as a core, that should tell you something. I do have a marine 270 baby hemi I will be experimenting on soon though.
  23. olscrounger
    Joined: Feb 23, 2008
    Posts: 3,977


    Don't know much about these but we did buy a couple of 409 motors from boat shops in the 70's that had been run in drag boats. No problems with those.
    lothiandon1940 likes this.
  24. SEAAIRE354
    Joined: Sep 7, 2015
    Posts: 190


    If your referring to the aluminum block 470 that uses a BB ford head they were all closed cooling systems. If the riser failed then you could get raw water in the cylinders and have problems. I owned a machine shop on Long Island and over the years used marine engines in all kinds of racing/ street stuff. But as said only blocks that had closed cooling systems. Any thing that was raw water cooled got scrapped. There are many changes that were done depending on the manufacture. As mentioned the Chrysler stuff had the knurl on the crank done in the opposite direction for reverse rotation and that needs to be ground off. Chevy engines just used a different seal. On some of Hemi engines they used a gear drive for the cam and the crank won’t except a standard timing chain sprocket.

    Sent from my iPhone using H.A.M.B.
    alanp561 likes this.

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