Merc 170 Exhaust manifold/coolant reservoir gasket

[SDSeville]

I am replacing the gasket between the exhaust manifold and coolant reservoir on my 1986 merc 170 (3.7). Please tell me if I am reading the manual correctly. As I see it, you can replace the 2 gaskets and stainless steel plate with one seperator gasket (27-97542). It doesn't make sense, but that is what the picture seems to indicate.

 

[stonyloam]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

That is correct, but the gasket has been superseded with a single gasket. Which one you need depends on whether you have a cast iron or aluminum manifold (magnet will tell). Aluminum: http://www.mercruiserparts.com/showSpecialPicture.asp?pn=18272 pn 27-18272. Cast iron: http://www.mercruiserparts.com/showSpecialPicture.asp?pn=856705 pn 27-856705 (superseded 27-97542)

 

[SDSeville]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

Thanks Terry. So I need one of the new gaskets and no stainless steel plate?

 

[stonyloam]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

Thanks Terry. So I need one of the new gaskets and no stainless steel plate?

Correct, according to the current parts breakdown for your engine. My "87" has a aluminum manifold, so check yours. Here is the parts breakdown for your engine: http://www.mercruiserparts.com/selectDocs.asp?doc_nbr=12488 The parts you are looking for are under exhaust manifold and elbow. I have not see one in person, and am not sure, but I think the ss plate is built into the new single gasket. Good luck.

 

[SDSeville]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

My engine has a cast iron coolant reservoir and aluminum exhaust manifold (per the magnet). Based on my engine serial number, Sierra recommended (and I bought from iboats.com) their version (18-0113) of 27-97542/27-856705. They explained that the cast coolant reservoir (and engine sn) called for this part. Is this correct?

 

[stonyloam]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

I don't think so, but am not sure. I think all of the reservoirs are cast iron. If you have an aluminum manifold and the bottom of the reservoir looks like this: http://www.mercruiserparts.com/showSpecialPicture.asp?pn=98562A6 then you need the 27-18272

 

[SDSeville]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

Local marina is telling me 27-97542. They base it solely on the sn and not manifold material. Not sure what to do. I am going to the lake for 5 days soon and don't want to have a cooling system failure.

 

[stonyloam]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

Take it off and see, take the reservoir to the marina if you have to, that way you will get the right one for sure. This is (cast iron) one, : http://www.ebay.com/itm/MERCRUISER-..._Accessories_Gear&hash=item2c666143ee&vxp=mtr this is the other (Al) http://www.mercruiserparts.com/showSpecialPicture.asp?pn=98562A6 Note the differences in the gasket surface.

 

[stonyloam]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

Which one was it?

 

[SDSeville]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

Well, it had 27-18272. You were right Terry. Here are the pics.



But now I have a bigger problem than needing a new gasket. On of the bolts was partially frozen in the coolant reservoir and tore up the threads on the manifold a bit while I was removing it. Can the threads be cleaned out or do I need a new manifold now?

 

[SDSeville]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

Holy Crap!! Was just quoted $980 for a new manifold! Someone please tell me this can be fixed.

 

[stonyloam]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

Well, it had 27-18272. You were right Terry. Here are the pics.
But now I have a bigger problem than needing a new gasket. On of the bolts was partially frozen in the coolant reservoir and tore up the threads on the manifold a bit while I was removing it. Can the threads be cleaned out or do I need a new manifold now?

You certainly should not need a new manifold. What I would do is get a tap of the correct size and chase the threads of the hole, and get them cleaned up (not a bad idea to do on all of the holes) and see how they look. If it looks OK and holds the proper torque when you put it back together you should be OK. If not either a helicoil or drilling and tapping to the next size up should do it. It might be worthwhile to grab 4 new bolts from your dealer (29) here: http://www.mercruiserparts.com/Show...=EXHAUST+MANIFOLD+AND+EXHAUST+ELBOW(ALUMINUM) Good luck, and thanks, It feels good to right once in a while.

 

[SDSeville]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

Thanks Terry. I checked with the local marina and they would not even look at it. They said I just have to get a new one for $980. Luckily, I called my auto mechanic and he said to bring it over and he would take care of it. He looked at it and said it was just the top 3 threads that were badly messed up. He cleaned and chased the holes and said that I should get a bolt 1/8 to 1/4" longer than the original and it will hold the torque I need.

 

[stonyloam]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

Gerat! You know it kind of T's me off, no one wants to fix anything anymore, just toss and replace. They should try farming, they would be broke in a month LOL Enjoy the summer!

 

[SDSeville]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

The manifold worked perfectly. Everything is installed. However, I think I broke the temperature sending unit. I spun the tip where the wire connects when I was trying to remove the wire. Does that mean it is done?

The local shop does not have the merc part in stock but carries aftermarket sensors. The aftermarket sensors are sold by size and temp range. The size is easy, but how do I find out what the correct range is for my application?

 

[stonyloam]

Re: Merc 170 Exhaust manifold/coolant reservoir gasket

The normal operating range for your 470 is 165-200. But you would want to run in the 165-175 range. My gauge has never worked correctly, what is more important IMHO is noting what the gauge reads when your boat is running right and keep an eye on it, mark the gauge if need be, and if the temp ever starts to creep up, find out why and fix it. You could try soldering the wire onto the sender and give it a try.