4.3L Vortec mercruiser cracked block - swap with automotive engine block?

Discussion in 'DIY Marinizing' started by mmanning63, Jun 19, 2010.

  1. lilrobobx
    Joined: Aug 2011
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    Location: Hope Mills, NC

    lilrobobx Junior Member

    GM V6 262 Head Gasket
    FEL-PRO 17010

    Yep that is the gaskets i have, the core i can verify 100% not to be stainless steel, not sure about the fire ring...i did magnetic strength tests on them to see how well a magnet sticks, and got equal strength between the 2 head gaskets...the main difference to me appears to be on the price tag, just like the engines.
    No matter how you look at it, raw water cooled engines are at a much higher risk of failures due to the obvious situation, especially in salt as it is several times more corrosive when warmed.
    Just my couple cents.
    CDK,
    Too bad stainless exhaust manifolds are nearly 3 grand a pair or im sure every boat owner would love to have a set...
    Also, it would be nice to have closed cooling systems...tend to shy away from that price tag also, as they say, raw water cooled engines can last upwards of 10 years if well cared for(hold the salt) well thats probably close to the life span of a marine engine anyways pending the amount of use and abuse...that number may be higher or lower.
    They are still pulling up cast boat anchors from the ocean that have been there for nearly 100 years in pretty decent shape...so i think the cast iron will last quite a while
    So i do agree, gaskets are probably a weak link and its probably a good idea to replace them every few years just for peace of mind if nothing else, i dont have much choice as i cannot seem to get an engine to last more than a few months...i am on my 3rd engine this season.
     
  2. Frosty

    Frosty Previous Member

    Stainless steel is not a good metal for making exhaust and heat exchangers. It rusts and cracks in no time. You can buy copper heat exchangers , cast steel or alluminium. Well you can here!!!

    My 2 heat Yanmar exchangers are brass made in New York ---I dare not imagine how much they would be
     
  3. whitepointer23

    whitepointer23 Previous Member

    on ebay a couple of weeks ago there were a set of stainless exh manifolds for a 350 chev, they stated that all the corrosion had been removed and some holes welded up, pressure tested okay. [i think that tells us how good stainless manifolds are].
     
  4. Frosty

    Frosty Previous Member

    Yeah,-- worst thing ever, and these people that buy stainless anchor chain shackles or even swivels OH--- they are asking for a loss of boat.

    Stainless was invented for kitchen sinks and that's all its good for,--maybe salad bowls, ball point pens etc etc.

    PS knifes and forks too.
     
  5. CDK
    Joined: Aug 2007
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    CDK retired engineer

    All these negative waves are uncalled for guys!
    The stuff used for Chinese solar garden lamps is not the same as used in heat exchangers.
    This is the worlds leading supplier: http://www.alfalaval.com/Pages/default.aspx

    I have used one of their products in a twin Mercruiser installation for over 15 years. After I removed the engines and sold the sorry bunch on Ebay I cleaned the exchanger with hydrochloric acid and found it to be in impeccable condition.

    These guys also make the pumps and oil/mud separators for drilling platforms all over the world. No kitchen sinks, no ball point pens, no knifes and forks.
     
  6. IMP-ish
    Joined: Jan 2011
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    IMP-ish powerboater

    And for thin fast props.
     
  7. broke_not
    Joined: Jun 2008
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    Location: North Dakota

    broke_not Junior Member

    The oil pump situation is another thing that comes up frequently in these "marinizing" threads. My question is this: If you source an engine that's in good shape to install in your boat and said engine has good oil pressure, why is a high-volume pump necessary? I'm not "against" the idea...I'm just curious as to why it always comes up. Why does an engine suddenly need "more volume" when it's dropped into a boat? And since a "high volume" but "standard pressure" pump seems to always get recommended....how is that result ultimately obtained? Bearing clearances and the pump's relief spring are what determine the oil pressure. So if we drop in a high volume pump and the bearing clearances are fine, all we're doing is pumping the oil back to the sump....because the pump we chose was "standard" pressure.

    Where is all of this *extra oil volume* going if the engine clearances haven't changed and the replacement pump we've chosen has a "standard pressure" relief bypass?
     
  8. powerabout
    Joined: Nov 2007
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    powerabout Senior Member

    Cupro nickel is what real ones are made from
     
  9. CDK
    Joined: Aug 2007
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    CDK retired engineer

    There is of course no reason to install a high volume pump. The oil pressure is maintained by a spring above the bypass valve. If the engine is in good condition and has the proper oil viscosity, the standard pump has enough capacity to meet the demand.
    If the mounting angle differs considerably from the one in a vehicle it may be advisable to modify the oil pickup tube, especially for a planing craft.
     
  10. Frosty

    Frosty Previous Member

    Oil pressure relief --not bypass . The by pass is in the filter.
     
  11. powerabout
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    powerabout Senior Member

    correct and no, the bypass in a Chev is in the oil filter adapter bolted to the block not the filter
     
  12. lilrobobx
    Joined: Aug 2011
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    lilrobobx Junior Member

    Well, it may not be necessary unless the bearing clearances are in fact looser which i still have no fact of that, but that is what i understood the mercruiser engines come with (i looked into a aftermarket replacement and the p/n i was given was that of a HV pump)...In theory, it seems that they would end up with the same result at high RPM's A stock volume must build volume/pressure to a certain RPM, and then if the pressure were to get to the point it is too high, it must release it, so at whatever RPM that may be, Anything beyond that must be the same volume. In an engine that is running higher RPM's, if they are both standard pressure, then they would release pressure at the same time, leaving the extra volume only at the RPM's prior to the release of the pressure?? Pressure and Volume have to work together, it cannot possibly build more pressure until the volume at which it pumps, comes under pressure...and if it cannot ad more pressure due to the relief valve, then the volume could end up the same in the higher RPM's...whats your thought?
     
  13. CDK
    Joined: Aug 2007
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    CDK retired engineer

    My old Porsche has an oil pressure gauge, calibrated in bars (1 bar=14.5 psi). After a cold start it jumps to 4 at idle and stays there at any rpm. Once the operating temp has been reached it shows 2 bars at idle and goes to 4 at a little over 1000 rpm. And it stays there until 6000 rpm.
    It means that from 1000 rpm onward an increasing amount of oil is pumped around without taking part in lubricating the engine. The valve is clearly set at approx 60 psi which is a bit higher than for most engines, but the bearing load probably calls for it.

    Replacing the pump with one twice as big would give 60 psi at warm idle between 650 and 1000 rpm where nobody needs it, but there is no advantage whatsoever at higher speeds.
    It could be that the aftermarket pump for a Mercruiser has slightly higher gears because it is supposed to be installed in a worn engine. There it might do some good.
     
  14. broke_not
    Joined: Jun 2008
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    broke_not Junior Member

    I'm thinking it's unnecessary. I *kind of* asked the question to see what kind of "boat stuff" one of the experts would post. Usually when questions like the one I asked are posted on a boating forum, somebody will chime in with the differences in marine versus automotive use and duty. I expected an answer along the lines of, "A boat engine is much different than a car engine. In a car, you would have to be traveling uphill towing something in order to simulate the type of load a boat engine is under....."

    I was going to reply to that kind of answer by saying that we've all seen trucks and cars pulled over along the road on grades while towing trailers and such. The hoods are raised to alert other drivers that there are mechanical difficulties of some sort so everyone can pass safely. The thing is, none of those difficulties along the road while operating under higher loads/temperatures has ever occurred because there was a lack of available oil pump volume. Back before EFI, elevated loads for extended periods could result in vapor-locking. Even nowadays with all of the computer controls, engine overheating can still result in extreme load situations at higher ambient temperatures. Or, if the operator doesn't pay attention to the vehicle manufacturer's towing instructions, the transmission can be run hot enough to damage it.

    Insufficient engine oil pump volume though? Nope...have never seen it on a stock engine that's in serviceable shape operating in any condition a stock engine would ever be operated in. A component as critical as the engine's oil pump isn't going to be of a capacity or quality that is-so-close-to-being-inadequate-that-we-need-to-upgrade-it-so-we-can-sleep-at-night.

    You're not *fixing* anything that's currently *wrong* with your otherwise-sound engine by installing a high volume oil pump.

    Oil pumps aren't expensive at all, so the dollars aren't the issue I'm addressing. I was more interested in exploring, (or exposing), another "special boat engine part" issue.



    ;)
     

  15. CDK
    Joined: Aug 2007
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    CDK retired engineer

    OK broke_not, here we go:

    A boat engine is much different than a car engine.
    There is fierce competition between car makers to improve both performance and fuel economy, resulting in smaller engines, radical design changes and superior materials. In most countries there is legislation for pollution, safety and protection against theft that no boat engine could comply with.

    And there is a vast number of car magazines and TV programs, where well educated journalists spot any weakness and expose it. A car maker introducing a new model with a cast iron engine, low mounted crankshaft and a carburetor is quickly exposed and on his way to bankruptcy.

    Some will say that boat engines only use proven technology, but that is a euphemism for outdated leftovers from the car industry.
    There are numerous reasons as to why the situation has developed the way it has, like a smaller market, less competition and boating magazines that focus on sleek design and kitchen equipment.
    But the main cause is profit.
    Where the car industry works with small margins, boat engines have a retail price tag as if every part is gold plated. The boat builder who signs a contract for next season's models, gets his engines for far less than half the published price and the engine maker is still making a good profit.
    So to keep the ball rolling he buys cheap, outdated designs, assembled in low labor cost countries and builds a large marketing show around it, making extensive use of the word MARINE.
    Included in the strategy is an even larger profit margin on spare parts, like asking $400 for a $40 alternator or starter, so the whole chain of trade will repeat the same song, mostly because of ignorance, sometimes against better judgement.
     
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