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boat crazy

2005 SSi 6.2 MX MPI Brav 3 Impeller(Sea Water Pump)

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On 10/4/2018 at 6:51 AM, Wingnut said:

Two ways I've seen an impeller get so hard, so fast. First, cheap aftermarket impellers are out there which are not quality EPDM base material and I will only use an OEM piece sourced from a high volume supplier so I know I'm getting a fresh one. Secondly is cheap pink anti-freeze. I use either Prestone marine RV, which now is hard to find, or Sta-Bil marine RV which WalMart has. They are both Propylene Glycol based and will not stiffen the impeller. Mercriuser brand Marine is OK too but expensive. As I've mentioned before, I have installed a pressure gauge on the discharge side of the raw water pump at the power steering cooler fitting so that I can monitor the health of the impeller in real time and mine gets changed every 4 years based on seeing a slight reduction in delivery pressure at idle. Even then, old impeller is soft and at a glance looks like new. I think you are spot on about your non-toxic antifreeze killing your impeller. Some of the dollar store RV brands are even alcohol based, and none of them have inhibitors added to help protect engine cooling system internals.  W

Thanks for the Info Wingnut.  I was suspicious this cheaper pink stuff may be the culprit 

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On 10/4/2018 at 6:59 AM, Wingnut said:

If your rubber exhaust hoses are toasted, then my bet is the exhaust flappers at the entry to the Y-pipe are either burnt, or melted and gone. They are stainless steel swing doors and are jacketed in rubber so they can operate quietly. When they see excessive heat, the rubber at the hinge point melts, and the flapper drop down into the exhaust passage, and can even make it all the way down to the out drive. When you remove the back two 4" hoses you should see them sitting there on both sides.  W

Wingnut...you are on it !  Yup, from the schematic of the area I'm working on, it shows these "shutter-flap" or swing doors.  Figured, I see these when I took the boots off to replace them.

After I took the boots off the port side, I was anxious to see what this swing door assembly looked like, got myself real small so I could get back in that area and, yup.......

......they're gone, non-existent.....Thought maybe the swing doors we're not part of my assembly, but after reading your post wingnut, realize, they should be there.

 

1.  What does this swing door do ?  

2. Whats the issue if I operate the boat without these....Haven't taken apart the starboard side boots yet, but I'm sure the SB side is gone too.

3.  Is the non-existent swing door jammed up somewhere is the "Y" pipe ? !!  is it retrievable ?  Hard telling how long these swing doors have been missing.  Had the boat for 10 years now,    

    and never has these part disassembled. 

 

Thats for all your tips and help !

 

BC

 

 

 

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A stronger exhaust exit pulse has an equal and opposite return pulse called reversion. Excessive reversion creates cylinder charge dilution, and thus has the effect of softening the mid-range and bottom end. This situation is exacerbated with the quench effect created within a water cooled (wet) exhaust stream. As an engine nears WOT RPM’s, the exhaust signal is strong enough to overcome the effects of reversion. During heavy deceleration like in an emergency situation, a momentary vacuum is created within the exhaust manifold which can actually suck sea water up into an open exhaust valve. Some engines have elevated exhaust risers designed to combat this along with internal baffling, and some systems such as yours use exhaust shutters which act as quick acting check valves. When they dislodge and disappear, they end up at the base of the transom plate exhaust passage, and by tilting your drive all the way up, and removing the exhaust bellows you should find them. On the newer boats with exhaust sleeves, they will drop out as soon as the drive is fully raised. Get a set of new ones as they are not expensive. Sea water in a engine cylinder is never a good thing. #7 per attached link.   W

 

https://www.marinepartsplus.com/catalog/mercruiser/serialize(value)/6.2L_MX_MPI_BRAVO/884717003/12840-290

 

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On 10/5/2018 at 6:01 PM, Wingnut said:

A stronger exhaust exit pulse has an equal and opposite return pulse called reversion. Excessive reversion creates cylinder charge dilution, and thus has the effect of softening the mid-range and bottom end. This situation is exacerbated with the quench effect created within a water cooled (wet) exhaust stream. As an engine nears WOT RPM’s, the exhaust signal is strong enough to overcome the effects of reversion. During heavy deceleration like in an emergency situation, a momentary vacuum is created within the exhaust manifold which can actually suck sea water up into an open exhaust valve. Some engines have elevated exhaust risers designed to combat this along with internal baffling, and some systems such as yours use exhaust shutters which act as quick acting check valves. When they dislodge and disappear, they end up at the base of the transom plate exhaust passage, and by tilting your drive all the way up, and removing the exhaust bellows you should find them. On the newer boats with exhaust sleeves, they will drop out as soon as the drive is fully raised. Get a set of new ones as they are not expensive. Sea water in a engine cylinder is never a good thing. #7 per attached link.   W

 

https://www.marinepartsplus.com/catalog/mercruiser/serialize(value)/6.2L_MX_MPI_BRAVO/884717003/12840-290

 

Thanks Wingnut, Excellent explanation !    I have a pair of swing doors on the way.  The only part left in place was the metal hinge strip and some toasted end grommets.

 

In terms of the winterizing fluid ( pink stuff ), I see a few of the "marine/RV" products on the shelf that contain propylene glycol and also claim that it contains no alcohol.

Therefore, is it safe to say that any of the products that contain pure propylene glycol are OK to use in a marine engine and be non-hardening for pump impellers ?

The prestone is available,  but at 47, its not practical.  I see other bonafide alcohol-free marine engine antifreeze products on the market that are a bit more reasonable at 32,

Still somewhat costly.  Long story, short...whats everyones thoughts on the pure propylene glycol and its compatibility with our boats' engines internals as well as impellers and seals

 

Thanks !

 

BC

 

 

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11 hours ago, boat crazy said:

Thanks Wingnut, Excellent explanation !    I have a pair of swing doors on the way.  The only part left in place was the metal hinge strip and some toasted end grommets.

 

In terms of the winterizing fluid ( pink stuff ), I see a few of the "marine/RV" products on the shelf that contain propylene glycol and also claim that it contains no alcohol.

Therefore, is it safe to say that any of the products that contain pure propylene glycol are OK to use in a marine engine and be non-hardening for pump impellers ?

The prestone is available,  but at 47, its not practical.  I see other bonafide alcohol-free marine engine antifreeze products on the market that are a bit more reasonable at 32,

Still somewhat costly.  Long story, short...whats everyones thoughts on the pure propylene glycol and its compatibility with our boats' engines internals as well as impellers and seals

 

Thanks !

 

BC

 

 

Just bought a case of Prestone for $50 with free shipping.  6 gallons    Walmart has Sta-Bil branded for 5/gal in the store and have Prestone listed for 42/gal online. I don't get that one but if you search New Jersey Wholesale Supply, they have case quantity on the cheap with free shipping.

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