Thermostat Housing Check Balls

[Red955i]

In reading an older post I saw where Bondo and All Dodge were speaking about the Check Balls in the Thermostat housing and one of them commented they were not used on Alpha One Gen II. So here's my question......

1995 Searay twin 4.3 Mercruiser 4-bbl (no original serials) with Alpha One Gen II drives. Both original motors were replaced in 2003 with Quicksilver Rebuilds. They have a tag on them saying Part# 807736 11 Bored .40 Mains .10 Rods. .10 S/N 90001?0 (second to last digit cant read). These are newer Vortecs than what was in boat originally. And yet, in installing these motors they didn't upgrade the cooling, nor did they keep the 1995 system. Both engines have the thermostat housing as found in the late '80s. Warm water system. 6 bibs. T-fitting with check balls going to risers

The above may or not be necessary for my question since it has ran that way for 17 years. Just giving you the full picture.

Port engine runs cool except for elbows which you cannot touch with your hand. Manifolds and elbows are new. No riser extension. Restrictor gasket. New exhaust flappers. Exhaust Tube not bellows. Ran garden hose is Y to make sure exited and didnt back up. Hoses and clamps are new. Impeller is new. Circulatory pump is new. Swapped Check balls and Springs from Starboard (no change) Clear hose from Thermostat housing to bottom of starboard side (of port engine) manifold shows air bubbles. Not a ton, but steady. Gut says head gasket. Compression test shows 160-170 per cylinder. Was going to block the four hoses to risers/manifolds and pressure test engine but couldn't generate enough pressure with hand pump. Will have to wait till boat is out to use compressor. Any ideas? Opinions are appreciated. Many thanks

 

[alldodge]

Which thermostat do you have, design 2 ?

 

[Red955i]

Which thermostat do you have, design 2 ?

View attachment 328785

Design #1

 

[alldodge]

There was a change over from the design 1 to design 2 in 1993.

Those thermostats can get clogged, even easier if there is salt. It uses a small passage design to restrict water flow to the manifolds. They were also used on some of Merc later racing motors like the 500EFI.

The manifold to elbow should use gasket which has 2 slots and 2 small holes 27-863724

Note how the thermostat housing and sleeve (item 7) is positioned and gasket



I would lean toward replacing housing with design 3

 

[Red955i]

There was a change over from the design 1 to design 2 in 1993.

Those thermostats can get clogged, even easier if there is salt. It uses a small passage design to restrict water flow to the manifolds. They were also used on some of Merc later racing motors like the 500EFI.

The manifold to elbow should use gasket which has 2 slots and 2 small holes 27-863724

Note how the thermostat housing and sleeve (item 7) is positioned and gasket

View attachment 329074

I would lean toward replacing housing with design 3

There was a change over from the design 1 to design 2 in 1993.

Those thermostats can get clogged, even easier if there is salt. It uses a small passage design to restrict water flow to the manifolds. They were also used on some of Merc later racing motors like the 500EFI.

The manifold to elbow should use gasket which has 2 slots and 2 small holes 27-863724

Note how the thermostat housing and sleeve (item 7) is positioned and gasket

View attachment 329074

I would lean toward replacing housing with design 3

Thanks for reply...I am confused though. You are saying to change from #1 (6 bib...warm water) to #3 (4 bib..cold water)? So eliminate the hoses to the elbows? From what I can tell looking at Mercruiser parts book...the boat came with design 3... For some unknown reason...when it was repowered in 2003 with Quicksilver rebuilds (which are later Vortec 4.3's) they used the Design #1...still a 6 bib system but a much older design...And yes with the 6 bib, and no riser extensions we are running the restrictor gasket between manifold and elbow

 

[alldodge]

Who knows why Merc does what they do, but just guessing is they had several left over design 1's. Design 3 was used later and still is. Change over would be easy enough but could also try taking your housing and put in some a cleaning solution, maybe muriatic acid, rust desolver or if its barnacles the buster stuff

 

[Red955i]

Who knows why Merc does what they do, but just guessing is they had several left over design 1's. Design 3 was used later and still is. Change over would be easy enough but could also try taking your housing and put in some a cleaning solution, maybe muriatic acid, rust desolver or if its barnacles the buster stuff

Thanks...but if I were to change...are you still recommending I go to #2 (4 bib) and eliminate the bleed off direct to risers?

 

[alldodge]

I would go to design 3 and remove the elbow connection

 

[Red955i]

I would go to design 3 and remove the elbow connection

Ok many thanks....at that point...if I'm not mistaken...I would run the full open riser gaskets .vs the restrictors

 

[alldodge]

Yes, full open
The port side may still be a tad bit hotter then the starboard at idle. Its just water flows easier that direction, but can keep your hand on it

 

[Red955i]

Yes, full open
The port side may still be a tad bit hotter then the starboard at idle. Its just water flows easier that direction, but can keep your hand on it

Ok here's another question.... Do you know how the internal water passages run in a 4.3? are the straight back from circulatory pump and then up to rear of head? Reason I ask....Pull the blue plugs out of both manifold....lots of water...pull the plug out of port side of engine ....tons of water (though had to pick through a little carp to get it all) pull the starboard plug....not a drop...pick it...not a drop and pick goes full in. So why do I have no water on one side of block? I know one plug doesnt drain both sides. Remember..I have air in engine...no water in oil....raw water cooled. Overheat at high RPMS >3000 runs cool below 3000 but risers are boiling. Sounds like a head gasket...but...before I even consider that need to figure this out. If gasket is blown, and blown on that side...it will only blow again if there's no water to that side. Block may be clogged...or maybe cracked? Thoughts?

 

[alldodge]

haven't drained a V6 in a long time and when I do my BB there is always some water the comes out both sides, just not as much on the second side.

I think your good, but to verify, put Port plug back in and then pour water into the thermostat housing and see if water comes out the starboard side

 

[alldodge]

Could check the circulating water pump to see if the vanes inside the pump have come loose from the shaft. Normally when this happens the motor just over heats. If a head gasket was the issue, then the heat/water still comes together in the thermostat housing and splits almost even.

 

[nola mike]

Winterized my 4.3 last week and noticed the same thing. The starboard engine plug was the last removed. I was back out today though, so will winterize it again next week. Going to start with that plug and see what happens

 

[Rick Stephens]

I pull block drains first and always get solid streams out of both.

 

[Lou C]

I ran into this with my old 4.3 after about 15 years of raw water cooling on the starboard side never on the port side. Port side always drained well starboard side was less or just a trickle. On the starboard side there is an additional fitting to change the angle of the drain fitting, I think because the older style starters were bigger, or the brace they used got in the way. When I had the heads off 3 years ago I was able to get down in there with a couple of different picks and really dig out the rust. Since then it drains as well as the port side. So water definitely SHOULD come out. I'd try to get down in there and use a couple different shape picks and really dig out that fitting. I did not have to remove it. Not sure if Mercs used this as well but for sure they were on OMC's version. If you look closely you can see it in this pic of the starter.

 

[nola mike]

I ran into this with my old 4.3 after about 15 years of raw water cooling on the starboard side never on the port side. Port side always drained well starboard side was less or just a trickle. On the starboard side there is an additional fitting to change the angle of the drain fitting, I think because the older style starters were bigger, or the brace they used got in the way. When I had the heads off 3 years ago I was able to get down in there with a couple of different picks and really dig out the rust. Since then it drains as well as the port side. So water definitely SHOULD come out. I'd try to get down in there and use a couple different shape picks and really dig out that fitting. I did not have to remove it. Not sure if Mercs used this as well but for sure they were on OMC's version. If you look closely you can see it in this pic of the starter.
View attachment 329340

I didn't have the fitting on mine (I have an automotive block).

 

[Lou C]

I guess for whatever reason that side clogs more easily so get a set of picks from Harbor Freight or similar and take some time digging out that drain hole. When it’s clear it will drain about the same as the port side. Since I really cleaned it out when I had the heads off 3 years ago I haven’t had that problem....and before that it was a frequent concern but since I always filled it up with -100 marine antifreeze which stays liquid down to -45 or so and that probably prevented the water that did not drain from freezing....