OMC 5.7 cooling system

[ab59]

Can some one tell me why running a boat with a 5.7 in it with a closed cooling system would get salt corrosion in the exhaust manifolds and the Y tube if it were operated in salt water ? I have been told this several times here but I guess I'm just too stupid to figure it out. Seems to me that a closed system does not allow raw water into the manifolds period so I guess I need some one to explain this to me so I can understand . Also why do I need to run shutters.

 

[tpenfield]

There are 2 types of closed cooling systems . . . 'FULL' and 'HALF'. The 'half' systems run the coolant through the engine block and cylinder heads only. The sea water, after going through the heat exchanger, goes to the exhaust manifolds then up to the elbows and out the exhaust (Y tube).

A 'full' system runs the coolant through the engine block, heads AND the exhaust manifolds. The sea water goes through the heat exchanger and then straight to the exhaust elbows (risers) and then out the exhaust tubes (Y tube). There is a 'block off' plate that separates the exhaust manifold from the exhaust elbow, so never the coolant and sea water shall meet.

Here is a link to a page with further explanation and diagrams . . . http://www.orcamarine.com/faq_and_tips.html

 

[tpenfield]

Forgot about the shutters. . . they prevent surges of water from making its way up the Y-tube and into the exhaust, where it can reach the exhaust valves. This sort of thing happens when slowing down or when a wake hits the boat and it rocks up and down. Shutters are not an absolute prevention of water getting to the inside of the exhaust, but they help.

I find that the shutters last only a few years, but eventually the exhaust wins out and the shutters disintegrate. My boats have probably run more without the shutters intact than they have with them. Will a boat mechanic say you need them? Yes, they will.

 

[Scott Danforth]

the shutters help prevent water ingestion from backing up or a wave hitting the back of the boat. they are essentially a check valve

 

[ab59]

OK , I just climbed out of the boat where I found where the raw water is entering the system which finally explains some of my confusion about the system. However I have found another diagram of the closed systems that show a raw water pump that is not on my engine so now I am left to wonder if I am missing parts of the system or this is just another variation of her same thing that does not require that pump. All my system has is a standard water pump, a tank , a power steering oil cooler and necessary hoses. The hose coming out of the ps cooler goes directly to the tank and not to a pump. The link I will attempt to leave shows a pump before the tank that I do not have.
http://www.cpperformance.com/
If this schematic is correct then I am missing parts. If it is only two variations of a closed system then maybe I'm not missing parts. If anyone knows please let me know.

 

[ab59]

This is what I have to work with.------




there are no extra pumps for raw water or separate heat exchangers

 

[tpenfield]

I just answered your other thread about running the engine on a pallet, and provided some details about the cooling system. A few more pictures would help, as
I am not seeing all of the engine from various angles. there should be more hoses, so perhaps you are missing some parts.

What is the history of this engine/boat? not sure we asked that yet?

Also that heat exchanger looks a bit small (sort of hard to tell for sure) so I'm thinking it is a 'half' system :noidea:

 

[ab59]

Thank you very much as I think I am beginning to understand this system. If I understand this correctly the " raw water pump " is in fact the Impeller in my outdrive that picks up raw water and circulates the water through the system and out the exhaust through the turn backs , rite ?? That is why there is no pump up front , driven by a pulley. That said then another point of confusion was that the schematics show that the heat exchanger and tank are separate but they are in fact the same tank, rite ?? Thanks to your extremely thorough explanation of this system in my other thread about running the engine out of the boat I think I understand now and thank you very much , I was getting more than just a little frustrated. Some times I think it would be easier to throw a pebble through a cement block wall then to get new knowledge through this thick skull of mine.
I will however go out and hang the exchanger and then take some more pictures in a few minutes.

 

[Scott Danforth]

that is a half system. most likely built by monitor products in Brooksville FL

 

[ab59]

rite or wrong here is what I've got -----

 

[Scott Danforth]

looks like an aftermarket 4-pass 3" or 3-1/2" heat exchanger.

inlet should be the little 45 degree elbow. if you pulled the end cap off, you would see the divider (x with one leg missing). the other end just has a turn-around divider

the outlet you have tee-d together and feeding the manifolds

 

[ab59]

ran across this article from Volvo about shutters and although I have decided to install them anyway ( if I can finally get some that fit right ) I thought this was an interesting bit of information. Please forgive me if I have represented this in an up professional way. I do not want to be further rep-remanded by the moderators.
Edit:
Found the service bulletin from Volvo Penta dated 9 of 1999

Service Bulliten
Date: 9?1999
3.0, 4.3, 5.0, 5.7, 7.4, 8.2 Gas Sterndrive Engines

After extensive testing Volvo Penta has found that the exhaust flapper valve located in the exhaust pipe is not effective
in preventing water ingestion. The valve has a short lifespan and has been known to disconnect from its pivot
rod and clog the exhaust system. Therefore, Volvo Penta will no longer include an exhaust flapper valve on the
engines listed above.
The exhaust flapper valve (3853864-1), pin (3852753-
7), and bushings (3855517-3) will no longer be available
through Volvo Penta Parts. New exhaust pipes
from our parts system will be delivered without the
exhaust flapper valve. Do not attempt to install an
exhaust flapper valve in a new exhaust pipe.

Any thoughts

 

[tpenfield]

I tend to agree that they are not very effective, except in certain circumstances and only when they are new. Otherwise, they just partially disintegrate and clog up the exhaust.

 

[HT32BSX115]

Can some one tell me why running a boat with a 5.7 in it with a closed cooling system would get salt corrosion in the exhaust manifolds and the Y tube if it were operated in salt water ? I have been told this several times here but I guess I'm just too stupid to figure it out. Seems to me that a closed system does not allow raw water into the manifolds period so I guess I need some one to explain this to me so I can understand .

ALL closed cooling systems will exit raw (sea if in salt) water out the risers and into a Y-pipe if installed.

 

[Scott Danforth]

ran across this article from Volvo about shutters and although I have decided to install them anyway ( if I can finally get some that fit right ) I thought this was an interesting bit of information. Please forgive me if I have represented this in an up professional way. I do not want to be further rep-remanded by the moderators.
Edit:
Found the service bulletin from Volvo Penta dated 9 of 1999

Service Bulliten
Date: 9–1999
3.0, 4.3, 5.0, 5.7, 7.4, 8.2 Gas Sterndrive Engines

After extensive testing Volvo Penta has found that the exhaust flapper valve located in the exhaust pipe is not effective
in preventing water ingestion. The valve has a short lifespan and has been known to disconnect from its pivot
rod and clog the exhaust system. Therefore, Volvo Penta will no longer include an exhaust flapper valve on the
engines listed above.
The exhaust flapper valve (3853864-1), pin (3852753-
7), and bushings (3855517-3) will no longer be available
through Volvo Penta Parts. New exhaust pipes
from our parts system will be delivered without the
exhaust flapper valve. Do not attempt to install an
exhaust flapper valve in a new exhaust pipe.

Any thoughts

volvo drives and the volvo/omc joint venture drives are different then the OMC drives.

what drive specifically do you have.

 

[ab59]

here is a pic of the tag on the outdrive otherwise I do not see any other identifying numbers .

 

[ab59]

HT---- when I asked that question I did not understand how the system worked but after getting some very good information from tpenfield I now understand but thank you for responding.

 

[ab59]

CScott Danforth--- When I posted the pictures I thought that they could be magnified but when I just tried I saw that they cannot so here is the bad news for me--
Cobra outdrive model # 985271---5.0L.
the 5.0 has been a bone of contention for a while now. the old block says its a 5.7 but the stamped numbers up front below the head on the left has numbers that come back as an OMC 5.0L so I just do not know what to think. Now that I see the 5.0 on the outdrive I need to know if the outdrive can handle the 5.7 and I have heard both yes and no so not sure what the correct information is.

 

[bruceb58]

The exact same drive was used on the 5.7 and the 5.0 except for the gear ratio. You will probably be ok but with a slight increase in prop pitch. Back in the day when I had a 5.0 Cobra, I was going to jump up to a 5.7 but sold the boat before I ever needed to.

 

[ab59]

thanks 58 this put a knot in my stomach . it seems like every thing on this boat , with the exception of the hull , was not working . Right down to the alternator .