88 Mercruiser 4.3 V6 Water in oil and exhaust manifold

macgyver681

Recruit
Joined
Jul 22, 2014
Messages
5
2000 Larson 18' Bowrider 1988 Mercrusier GM 4.3L V6 (Rebuilt Block up 4 years - 2 seasons ago) sat for 2 years Raw water cooling Just bought a boat with a bad motor so I could swap my good motor from my old boat into it. Old boat was crushed by a tree during Hurricane Sandy. Swapped motor into it last weekend. Replaced exhaust flaps before I put it in, they were shot. Outdrive on 2000 boat is good. Tested with ears on land and motor ran good and oil looked clear. Took it out the other day and the second time out I noticed oil was suddenly milky and seemed higher. Did oil change and took it out again on Sunday. Cruised around for awhile and drove fine. No sudden stops. Stopped and floated for about an hour. Went to re-start and its hydro-locked. Pulled exhaust riser off and there is an inch of water in the manifold and pulled plugs and one cylinder is full of water. Checked flap on that side and it looks good, still springy and doesn't look to be binding. Ideas on what is causing water in exhaust and how its getting in oil? Connected or coincidence?
 
Last edited:

dingdongs

Chief Petty Officer
Joined
May 29, 2009
Messages
649
remove water from cylinder and put some wd40 and some oil in it to stop it rusting.remove all plugs and spin engine over paying particular attention to water filled cylinder and then do a compression test on all cylinders..report back and a new manifold is inevitable but would do the pair if all the rest of the engine checks out with good compressin across the board.
 

macgyver681

Recruit
Joined
Jul 22, 2014
Messages
5
No water currently in cylinder but WD-40 sounds like a good preventative measure. I'll have to get back to you on the compression. I pulled the offending side riser and mainfold. Filled with water and waited. No obvious leaks into exhaust passages, though its not under any pressure.
 

NHGuy

Captain
Joined
May 21, 2009
Messages
3,631
Try a cooling system pressure test. Block off the outlets and pressurize the inlet. Listen at the carb, exhaust and valve cover fill holes.
 

macgyver681

Recruit
Joined
Jul 22, 2014
Messages
5
Update I just did a compression test. Odd results. Here it goes:
Cylinder# Pressure
1 140
2 130
3 140
4 185 (A little water in there still i think)
5 135
6 125

I'm not really sure what the compression should be though...
 
Last edited:

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
2000 Larson 18' Bowrider 1988 Mercrusier GM 4.3L V6 (Rebuilt Block up 4 years - 2 seasons ago) sat for 2 years Raw water cooling Just bought a boat with a bad motor so I could swap my good motor from my old boat into it. Old boat was crushed by a tree during Hurricane Sandy. Swapped motor into it last weekend. Replaced exhaust flaps before I put it in, they were shot. Outdrive on 2000 boat is good. Tested with ears on land and motor ran good and oil looked clear. Took it out the other day and the second time out I noticed oil was suddenly milky and seemed higher. Did oil change and took it out again on Sunday. Cruised around for awhile and drove fine. No sudden stops. Stopped and floated for about an hour. Went to re-start and its hydro-locked. Pulled exhaust riser off and there is an inch of water in the manifold and pulled plus and one cylinder is full of water. Checked flap on that side and it looks good, still springy and doesn't look to be binding. Ideas on what is causing water in exhaust and how its getting in oil? Connected or coincidence?

Ayuh,..... Welcome Aboard,.... That sounds like rusted/ cracked manifolds, or possible the head,....

Ya need to pressurize the coolin' jacket of the block, insteada the compression test,.... It don't sound bad for a cold wet motor,....
 

macgyver681

Recruit
Joined
Jul 22, 2014
Messages
5
Update - Second compression test after WD-40 and a few squirts of oil as was suggest by someone

Possibly more confused about results:

Cylinder# Pressure
1 165
2 180
3 180
4 270
5 160
6 180
 
Last edited:

Bondo

Moderator
Staff member
Joined
Apr 17, 2002
Messages
70,465
Ayuh,.... Have ya pulled the manifolds yet,..??

Do ya have the one piece manifolds,..?? or manifolds, 'n risers,..??

Can ya rig yerself a pressure test for the Block,..??
That's the next step,....

Have ya Drained the block yet,..??
Sounds like #4 is still seein' water maybe,....
 

macgyver681

Recruit
Joined
Jul 22, 2014
Messages
5
Block is drained. One manifold and riser is off in pieces, no visible problems. Filled with water, no leaks. Two piece manifold. I'll try to rig up a pressure test next
 
Top