Trying to understand marine exhaust manifolds

[Glastron_V210]

Hi everyone.

I have a Mercruiser 260 (GM350) with the log type manifolds, and a closed or 'fresh water' cooling system. I'm trying to understand the water routing through the system, specifically the exhaust manifolds/risers.

If I look at my manual picture, the raw water seems to come from the leg pump, through the heat exchanger, then out to be injected into the exhaust stream at the manifolds somehow. Does this occur at the risers or in the exhaust manifold? It seems from what I've read, the gaskets between the manifolds and the risers are 'block off' type. If I understand it right there are passages between the risers and manifolds which are blocked off. Does the manifold contain the antifreeze mixture and the riser contain the raw water for injection? If I bleed the manifolds I get the green stuff! Is this what I should expect?


Thanks in advance,

Chay

 

[Don S]

Re: Trying to understand marine exhaust manifolds

It depends on how yours is setup. You could have manifolds and risers cooled with raw water, or manifolds cooed with antifreeze and risers cooled with raw water, post a picturre of you cooling system so we can look and determine what you have. A year Might help and even a Merc SN might help. But neither will tell anthing if it's an aftermarket setup.

 

[Glastron_V210]

Re: Trying to understand marine exhaust manifolds

OK, will do probably tomorrow when I get home (It's cold and dark out there right now!).

I appreciate any help.

Chay

 

[Bondo]

Re: Trying to understand marine exhaust manifolds

If I bleed the manifolds I get the green stuff! Is this what I should expect?

Ayuh,...

That alone says your Manifolds are freshwater cooled,+ the Risers are Raw water cooled...

 

[Glastron_V210]

Trying to understand marine exhaust manifolds Renamed 02 Sensor spacer

Trying to understand marine exhaust manifolds Renamed 02 Sensor spacer

Ok, so one more question then if you don't mind....


I'm looking at converting to a TBI EFI setup and I've seen spacers which allow the installation of a o2 sensor, like this one:

http://cgi.ebay.com/ebaymotors/Part....c0.m245&_trkparms=72:543|65:12|39:1|240:1318

It seems correct that at this point the exhaust stream would be dry, because the water is contained either in the jacket of the manifold or in the jacket of the riser. Whether it is a closed or open system doesn't really matter that much I guess.


It all depends at what point the water is injected into the riser. If it is injected towards the outlet of the riser it should be ok, because then everything before it would be dry. It makes sense it goes towards the rear, because if it came to the front it would pool in the exhaust manifold to some extent.



Do either of you guys know for sure whether this area would be dry or not?



Thanks,

Chay

 

[Bondo]

Re: Trying to understand marine exhaust manifolds Renamed 02 Sensor spacer

Re: Trying to understand marine exhaust manifolds Renamed 02 Sensor spacer

It all depends at what point the water is injected into the riser.

Ayuh,...

The Water enters the exhaust stream at the most Aft point of the risers....

Yes, it's Dry where you ask of.....

 

[Glastron_V210]

Re: Trying to understand marine exhaust manifolds

That's wicked good information, and very timely I might add. I just hit refresh, and like magic your answer was there!

This seems like a viable option for people who want to maximize their fuel economy via an 02 sensor.



I guess I'll have to add my build to the site!


Chay

 

[Bondo]

Re: Trying to understand marine exhaust manifolds

That's wicked good

Ayuh,.... Where's Home,..?? Sounds likea danm Maineiac to Me....

At the top, portside of the page is the "User CP" button,....

Go fill Your's in for Us.......

 

[Glastron_V210]

Re: Trying to understand marine exhaust manifolds

I'm up in Canader eh.

Specifically, Duncan on Vancouver Island, B.C.

Not a bad place to hang your hat if you're a boater.


Chay

 

[Tail_Gunner]

Re: Trying to understand marine exhaust manifolds

Umm i was not aware that ecu was able to use that type of sensor...Am i missing something here or do you intend to reprogram you system??

 

[Don S]

Re: Trying to understand marine exhaust manifolds

You aren't missing anything TG, the Mercruiser and Volvo ECM's are not setup for O2 sensors. They were never used in any of the TBI systems.
They never could keep them working for very long in a marine enviornment.
In the ad, (Dennis Moore and GLM) came this bit of info.

Aftermarket EFI (Electronic Fuel Injection) systems need an Oxygen Sensor to run in closed loop for maximum performance and fuel economy.

I have never heard of any of the aftermarket TBI systems actually working very well. They all seemed to run into problems.

 

[Glastron_V210]

Re: Trying to understand marine exhaust manifolds

It's hard to reprogram a Quadrajet! The biggest problem is finding the programming port!


Ok, seriously, I'm adding an aftermarket home brew TBI fuel injection. It's pretty simple...the plan is to strip the system from a 89-95 vehicle with a 350, add a external fuel pump and a return line to the tank etc. The original fuel map fuel delivery will be pretty close to the marine engine, and the 02 sensor will make up for the inequity, plus I can log data from the ecm and retune a replacement EEPROM (I have experience in doing this with GM V6 MPI, same vintage). The o2 sensor will help to adjust fuel to prevent any devestating detonation due to lean mixture if the marine engine has more airflow (I think it will use a bit more air top end). It'll have IAC to control the idle stock, which is a mojor upgrade on some of the 'coast guard approved' aftermarket TBI stuff.

At the very least I can tune the rochester better with a wideband. I'm getting worse fuel economy that my buddy with a 24', same setup otherwise (I have a 21). His boat also outperforms mine.



Chay