Exhaust manifold leak "replace core plug" or "replace manifold"?

jeanthomas

Cadet
Joined
Jun 26, 2015
Messages
6
Started up my 1994 Volvo Penta 3.0 GL engine (24' pontoon boat with I/O) for the first time this week and water started leaking from the first hole on the bottom(left) of the exhaust manifold (pic2.jpg). Turned off the engine and started taking pictures. I cannot determine if there was originally a "core plug" (or freeze plug) in this hole. (pic4.jpg is the 3rd hole from left to right on the manifold and does not leak). I do not see any cracks. (pic3.jpg is the second hole on the bottom of the manifold. It does not leak) Last fall, both petcocks/plugs were removed and water was drained for winterization. The boat ran fine last summer. Should I just plug this hole with a heavy duty rubber expansion plug, put in a new core plug or do something else? How should I test for other potential leaks/cracks?
 

Attachments

  • pic1.jpg
    pic1.jpg
    53.6 KB · Views: 0
  • pic2.jpg
    pic2.jpg
    66.6 KB · Views: 0
  • pic3.jpg
    pic3.jpg
    45.6 KB · Views: 0
  • pic4.jpg
    pic4.jpg
    54.2 KB · Views: 0

Grub54891

Vice Admiral
Joined
Jun 17, 2012
Messages
5,908
If there was a core plug, it's laying in the bilge.replace it with a brass core plug, run it and see if there are any leaks or milky oil. Then let us know how it went.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
47,296
pic 1 shows what looks like two cracks in it. could just be a scratch that rusted, however I would assume a crack until proven otherwise.
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
Last fall, both petcocks/plugs were removed and water was drained for winterization. The boat ran fine last summer.

Ayuh,.... I suspect the holes weren't probed with a screw or nail, resultin' not All the water drainin',....

As noted, the core plug oughta be in the bilge,....
Install a new one, 'n hope for the Best,....
 

jeanthomas

Cadet
Joined
Jun 26, 2015
Messages
6
Thank you for responding. You really helped me. The exhaust manifold core plug was replaced. Ran the engine at the dock for about 15 minutes. Manifold is not leaking. No milky-colored oil. I'm concerned about rusty debris getting caught in the thermostat housing or the impeller, causing the engine to overheat. Any suggestions?
 

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
Ayuh,.... The manifold is on the other end of the system,.....

Water goes From the impeller, to the t-stat housin', through the motor, 'n out the exhaust, or out the exhaust if the motor don't want anymore water at some points,...
The water never flows backwards, to rust, 'n crud can't get to the impeller,....
 
Top