1981 Mercruiser 470 (3.7) Water in all cylinders.

[yamhoss86]

Hi Everyone,

Thank you in advance for all your help.
I recently purchased a 22' fishing boat. The engine is a 1981 Mercruiser 470 (3.7).
To make a long story short. I ran the boat a few times and found out the exhaust manifold and riser needed to be replaced.
I replaced the exhaust manifold and Riser.
The issue now is that every time i pour Antifreeze into the reservoir, the antifreeze somehow gets into the cylinders after 2 gallons.
I don't know whats causing the antifreeze to go into the cylinders.
I have discussed the matter with some mechanics, most have suggested that the head gasket might be the culprit.
After doing some research i know the head gasket is not at fault as the antifreeze was in all of my cylinders.
Did anyone experience this in the problem? Feeling frustrated here....
Any advice/suggestion/resolution is welcome. Thank You.

 

[stonyloam]

Re: 1981 Mercruiser 470 (3.7) Water in all cylinders.

Incorrect exhaust elbow gasket (or poor seal). The coolant must be leaking into the exhaust manifold.
Must be leaking from one of the side coolant passages into the manifold. This is the gasket right? http://www.mercruiserparts.com/showSpecialPicture.asp?pn=997772

 

[yamhoss86]

Re: 1981 Mercruiser 470 (3.7) Water in all cylinders.

Incorrect exhaust elbow gasket (or poor seal). The coolant must be leaking into the exhaust manifold.
Must be leaking from one of the side coolant passages into the manifold. This is the gasket right? http://www.mercruiserparts.com/showSpecialPicture.asp?pn=997772

I have used two of the following gaskets along with the block off plate. Please see below.
Mallory 9-61415 Exhaust Elbow Gasket*-*Mallory*9-61415 - Mallory Engine Manifold Gaskets - Engine Manifold Gaskets - Engine Manifolds & Parts - Marine Exhaust Systems - Engine/Mechanical - Boatersland Marine
Is that the right one is should be using?

 

[Bondo]

Re: 1981 Mercruiser 470 (3.7) Water in all cylinders.

Ayuh,.... Welcome Aboard,... Is it a Used replacement manifold,..?? Did ya test it, before installin' it,..??

 

[stonyloam]

Re: 1981 Mercruiser 470 (3.7) Water in all cylinders.

Here is the OEM parts diagram: http://www.mercruiserparts.com/Show...&bnbr=6&bdesc=Exhaust+Manifold+and+Elbow(MCM) I wonder could it be possible that the block off plate went on backwards? Just speculating, am more familiar with the later version.

 

[yamhoss86]

Re: 1981 Mercruiser 470 (3.7) Water in all cylinders.

Ayuh,.... Welcome Aboard,... Is it a Used replacement manifold,..?? Did ya test it, before installin' it,..??

Thanks for the welcome. I got both parts used. I didn't pressure test it or anything like that. Just from the visual it looked good to me.

 

[yamhoss86]

Re: 1981 Mercruiser 470 (3.7) Water in all cylinders.

Here is the OEM parts diagram: http://www.mercruiserparts.com/Show...&bnbr=6&bdesc=Exhaust+Manifold+and+Elbow(MCM) I wonder could it be possible that the block off plate went on backwards? Just speculating, am more familiar with the later version.

I am pretty sure that the plate went on fine.
I remember checking to see if the angles were all right.
I also had trouble getting the bolts out when trying to replace the manifold, a few of the bolts broke in the middle.
I banged the block a few times with a rubber mallet, then used a blow torch and vice grip to get the remainder of the bolts out.
Maybe that could have made a crack somewhere? Idk.....

 

[yamhoss86]

Re: 1981 Mercruiser 470 (3.7) Water in all cylinders.

Bump...

 

[Eric 3.7LX Alpha 1]

Re: 1981 Mercruiser 470 (3.7) Water in all cylinders.

Your getting antifreeze on top of the pistons....

I'll post what the manual says:

1. Operator shut engine off at high RPM
2. Engine "diesels" or trys to run backwards
3. Rain water running into flame arrestor
4. Spark plug misfiring
5. Backwash thru the exhaust sytem
6. Improper engine or exhaust hose installation
7. Cracked exhaust manifold
8. Improper manifold to elbow gasket installation
9. Loose cylinder head bolts
10. Blown cylinder head gasket
11. Cracked valve seat
12. Porous or cracked casting

Since you have coolant in all holes.... that's eliminating some of those possibilities.

Your first post reads:
"To make a long story short. I ran the boat a few times and found out the exhaust manifold and riser needed to be replaced.
I replaced the exhaust manifold and Riser".

What was wrong that made you come to that conclusion and the big question is did you have coolant in all cylinders BEFORE you changed the manifold and riser???

 

[Bondo]

Re: 1981 Mercruiser 470 (3.7) Water in all cylinders.

Bump...

Ayuh,.... Drain the coolin' system, 'n pressurize it with Air, 'bout 15 psi,... then Listen,....

You Hear the leak, follow the sound,...

 

[yamhoss86]

Re: 1981 Mercruiser 470 (3.7) Water in all cylinders.

Your getting antifreeze on top of the pistons....

I'll post what the manual says:

1. Operator shut engine off at high RPM
2. Engine "diesels" or trys to run backwards
3. Rain water running into flame arrestor
4. Spark plug misfiring
5. Backwash thru the exhaust sytem
6. Improper engine or exhaust hose installation
7. Cracked exhaust manifold
8. Improper manifold to elbow gasket installation
9. Loose cylinder head bolts
10. Blown cylinder head gasket
11. Cracked valve seat
12. Porous or cracked casting

Since you have coolant in all holes.... that's eliminating some of those possibilities.

Your first post reads:
"To make a long story short. I ran the boat a few times and found out the exhaust manifold and riser needed to be replaced.
I replaced the exhaust manifold and Riser".

What was wrong that made you come to that conclusion and the big question is did you have coolant in all cylinders BEFORE you changed the manifold and riser???

Ahh i should have thought about this. I did not have coolant in the cylinders after i poured coolant with the old riser and manifold. I only did start to get coolant in the cylinders after i changed the riser and manifold. So i'm almost certain its the manifold. I changed the Riser because it was clogged and i replaced the manifold because it had heavy rusting.

 

[yamhoss86]

Re: 1981 Mercruiser 470 (3.7) Water in all cylinders.

Ayuh,.... Drain the coolin' system, 'n pressurize it with Air, 'bout 15 psi,... then Listen,....

You Hear the leak, follow the sound,...

The more i dig the more i am drawn to doing what you are suggesting.