Merc/4.3/Alpha I cooling, cracked manifolds, looking for options/better way

Discussion in 'Gas Engines' started by wood45s, May 16, 2017.

  1. wood45s
    Joined: May 2017
    Posts: 10
    Likes: 0, Points: 1
    Location: ga

    wood45s Junior Member

    Merc/4.3/Alpha I cooling, cracked manifolds, looking for options/better way

    Summary – I have to replace everything cooling related, so now is the time to make mods, improvements, etc.

    I am thinking of buying new Barr exhaust manifolds and risers. Recommendations?

    I’ve done web searches for boat cooling but haven’t found much info on theory/why it’s done the way it is. Any info would be appreciated.

    I was thinking of an add on engine driven seawater pump or maybe electric pump to replace the sterndrive impeller.


    Background – hope it’s not too long winded.

    I purchased a 1995 Starcraft Islander 221recently. Due to improper/incomplete winterizing, exhaust manifolds froze and cracked last winter (2016-17). The engine (vortec 4.3 with 12 bolt intake manifold) seems ok. The engine was rebuilt summer of 2016 with Chev s10 block and rebuilt heads due to busted/frozen block and heads. Also, new pistons, new roller lifters , rebuilt crank, but original cam. They installed used exhaust manifolds. Yes previous owner let it freeze two years in a row. The boat has not been in the water since engine was replaced.

    I’ve run it about 3-5 minutes with hoses bypassing exhaust manifolds and see no water leaking or in oil. The block was also pressure tested with about 5-10 psi of air and only leak found was 3/8 brass pipe plug in head, which I tightened. I disconnected stern water inlet to engine and piped water over the side due to busted exhaust manifolds, put in 160 thermostat with stern water input disconnected and with water fed from house faucet for input cooling water.

    Very little water was pumped by stern impeller, so I plan to replace impeller with oem Mercury impeller/seal kit. Looks like that kit has most seals, etc required for the lower drive. I’m trying to figure what else I need to replace in the lower right now. I have removed the stern drive.

    I’ll replace the gear oil with new synthetic. I have some Lucas synthetic now.

    I am thinking of buying new Barr exhaust manifolds and risers. I am always a fan of made in USA. Are there any common problems with Barr or are there other recommendations?

    Previous owner left the starter loose. So that bent the bolts and broke one tooth out of flywheel along with destroying the starter drive. I’ve fixed starter now but hear it going over that missing tooth.

    I will check engine alignment and maybe replace gimble bearing.

    I know this is boat not a car but I’m wondering why boats pump all that water thru the manifolds. Seems to me all that cool water would cool the engine good just circulating thru the block like a car. I’ve done web searches for boat cooling but haven’t found much info on theory/why it’s done the way it is. Are there any suggestions for useful websites? Any info would be appreciated.

    I was thinking of an add on seawater pump or maybe electric like mentioned in this post - Closed Cooling efficiency https://www.boatdesign.net/threads/closed-cooling-efficiency.56283/ Electric pump would require power only when engine was running, so would need to figure out where to get the power from and current draw. Also, I was thinking maybe could still pick up sea water thru the stern drive same as originally but have that water line feed into the electric pump.

    I guess with either of the above options the stern drive impeller would be removed?

    Also, I’m trying to find info on converting to closed cooling system. Seems to me a closed cooling system with antifreeze would be better. But maybe that would be too much trouble and expense. Looks to me like a closed system would use the same exhaust manifolds, but plumbing different.

    While it was running cold I was surprised to see water exiting thru the hoses that would be connected to the manifolds with no water thru the risers hoses Then when the thermostat started opening, some water started going out the riser hoses. I only ran it long enough for the thermostat to start opening.

    I do have Merc manuals 14 for the Alpha and 18 for the engine.


    Thx,
    wood
     
  2. 7228sedan
    Joined: Nov 2009
    Posts: 314
    Likes: 6, Points: 18, Legacy Rep: 60
    Location: New Jersey USA

    7228sedan Senior Member

    The systems work really well when they are 100% functional. Keep in mind that the manifolds need to be cooled as well, hence the water circulating through them in addition to the block/heads. Closed cooling systems are readily available as an aftermarket add on. The kits usually contain the heat exchanger, brackets, hoses, thermostat housing and gaskets/hardware. There are many online sites to purchase these conversion kits; for example ebasicpower.com, marineengineparts.com. There are 2 types of closed cooling systems: half or full. The half system cools the block, heads & intake manifold with antifreeze. While the full kits include the exhaust manifolds. In these cases, only the risers and heat exchanger get cooled with raw water. The nice part about these is that there is antifreeze in the block, heads, and manifolds, winterization is a snap. these kits typically run in the $1200-$1500 range. heat exchangers alone can cost 700 and up for these motors. With your alpha drive, the internal raw water impeller would only be responsible to flow the raw water through the heat exchanger and out to the risers. I'd think that the need for an add on raw water pump would be unnecessary in this instance.
     
  3. wood45s
    Joined: May 2017
    Posts: 10
    Likes: 0, Points: 1
    Location: ga

    wood45s Junior Member

    I am thinking of replacing my non dryjoint exhaust manifold/risers with dryjoint type. I’ve seen some recommendations that say this is a good option. Some say the dry joint type are a direct bolt on replacement, but others have had problems. Looks to me like the barr manifolds below should be a direct fit. They have the

    This is the one i’m thinging about ordering - http://www.marineengineparts.com/ex...ser-v-6-dry-joint-4-3-liter-with-7-riser.html
    These have the 7degree risers. Not sure what brand of gaskets those are. The riser gaskets are expensive and are listed as not reusable.

    barr list a bunch of standard and dryjoint.
    www.barrmarine.net/mercruiser.html
    and from ebasicpower by HGE.
    Manifold Exhaust Kit Mercruiser Dry Joint V6 4.3L 7 Degree Riser 2003-05 [BPIV6DJ7] - $799.00 http://bpi.ebasicpower.com/shop/index.php?main_page=product_info&products_id=2514
    Here’s the standard non dry joint manifold I was considering.
    Manifold Exhaust Kit for Mercruiser GM 262 4.3L V6 4 [BARV64MER] - $699.00 http://bpi.ebasicpower.com/shop/index.php?main_page=product_info&cPath=968_1196_1210&products_id=1259

    Any opinions?

    Thx,
    wood
     

  4. 7228sedan
    Joined: Nov 2009
    Posts: 314
    Likes: 6, Points: 18, Legacy Rep: 60
    Location: New Jersey USA

    7228sedan Senior Member

    My understanding of the dry joint exhausts is that they eliminate the choice between a solid gasket or one with passages between the riser & manifold. If you are going to convert to freshwater cooling, I think this makes sense. If you are going to maintain the raw water cooling, I believe there is a complete different routing of the hoses. In raw water cooling applications, the raw water enters at the bottom of the manifold, and flows up into the riser and out the exhaust. The dry joint would require an exit hose at the top of the manifold, and a inlet on the front of the riser to then exit the exhaust system.
     
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