Have 2 questions
1) A flow chart of a standard cooling system would be appreciated, but there are two hoses, that I can see/feel, going to the Catalytic exhaust. One hose goes to the bottom of the manifold. (Is that the coolants in?) The other hose is at the bottom of the riser. (Is that the coolants out or another in?)
2) There is a sensor at the bottom of the riser labeled , Rear exhaust water temp. If I disconnect the sensor will I have an alarm? Also what temperature would the sensor give an alarm?

Thank you for your time.
David.

Call a dealer , they can help you.

there is service 2 manuals for this app. I would buy them. really OSO is not the place for CATALYST engines how to, Sorry to be so direct but it is what it is, I am trained on 4 major OEM CAT gas engines and I promise more boat owners screw these engines up cause they think they know what they are doing but do not. Even techs can screw them up. The poppit valve(s) are very important for proper cooling here. You also will need a scan tool that is Mercruiser PCM 09 / PCM 112 very compliant inwhich Diacom is not the best scan tool to use here. Merc / G3 / dealer only is the best scan tool to use for Mercruiser CAT apps.

here is one big tip do not ever run a cat engine out gas - the chances of blowing a hole straight thru the cat substrake is more odds that it will. Prob have seen at least 12 to 14 of these failures in the past 7 years. Proper cooling thru out is more important than ever with all CAT apps,

BUP, what site would you you recommend to answer my question?

I have no idea as this is the only site I look at. And if I did look for marine detail info searching many online sites - How would one know if it was creditable to the T especailly with marine CAT engines. Heck there is 500 fault codes listed for a Mercruiser CAT engines. Old school MEFI 1 has 7 fault codes. just an example of indepth marine engines have been in the past 20 years.

Engine serial numbers are must as usual and even dealer reflash updates thru OEM Merc for the PCM has taken place with CAT engines. I seen a couple engines that has missed these.

The current CAT 6.2 is way different than the past CAT 6.2. The current Mercruiser engines production side not 1 GM part is used. Engine serial numbers are always a must.

Like I said the OEM service manuals per app and engine serial number will be your best bet here.

What is it your trying to do ? and why ? thanks

BUP, Wanting to install IMCO manifolds and risers. I have the O2 sensors by-passed. Just want to know about the rear exhaust water temp sensor and raw water hook up.

with using the stock pcm ??? will never happen nor run right WITH THE STOCK ECM AND STOCK TUNE.

what happened to the cats ?

and stock PCM runs in closed loop up to 80 percent throttle - without the O2 s monitoring a stock app will not run right and throw codes and possible engine damage.

Also word of warning totally against the law and up to a huge fine for deleting a marine emission control engine in the USA. EC marine engines are federal mandated.

In 2013 the EPA for all OBD-M ( Onboard diagnostics - Marine) catalyst equipped requires Torque Broadcasting .

if a marine dealer works on that engine and its non compliant in their shop with tools in hand knowing what it should be - huge fines can be brought upon to that service center. Just saying. I will be up front, sorry I am not going to follow along with advice on this one. Especially on a public forum with a federal mandated marine engine not being non compliant. Sorry man I have a marine dealer and manu LIC so I will not put my name on this one.

BUP, You're wrong.

1) There are aftermarket parts that would allow you to bypass the Cat Exhaust
2) You are able to operate a boat with out the Cat exhaust on a non emissions regulated waterway.
3) Don't assume anything........
4) All I asked for is info. You couldn't answer them. Not even the water flow.
5) Sorry to upset you.
6) The world is still in balance.

call Merc and the EPA. its the federal air emissions thats federal Law.

CP cat eliminator is the only thing that I know of being offered and its unproven and voids the warranty. They can get away selling it because of the disclaimer for OFF ROAD USE ONLY. you really are not going to gain anything if so not much.

and you did not upset me. sorry just passing on this cause I do have some stake here. good luck.

Don't forget Whipple reprogramming ECM. Check out their website. By the way I had service manual number 51 at my other residents. This manual tells me everything that I wanted to know.