Question about Mercruiser cooling system

[WetDog149]

Hi folks,

The boat in question is a 1996 Sea Ray with a 4.3L V6 Mercruiser and Alpha 1 drive.

When we run it on the hose, there is barely any water coming out of the port side exhaust. I wasn't sure if this was normal or if something in the cooling system is blocked.

I uploaded a video on youtube so you can see exactly what I'm talking about.

https://youtu.be/7Ubch1cEMTw

The port side exhaust manifold does get noticeably warmer than the starboard side when I touch them. The temp gauge on the dash doesn't indicate that it is overheating. It usually seems to sit at 160ish so I'm not sure there is a problem or not.

If there are some knowledgeable people on here that wouldn't mind taking a look at that short video then please share your opinions.

Also if someone could point me in the direction of a service manual or something like that for this boat that would be great. All the diagrams I was able to find on line seem to be slightly different to this engine.

Thanks!

 

[tpenfield]

Knowing your engine serial number will help with responses, but in general . . .

you don't always get a even balance of water flow between port and starboard, but if you are noticing the elbows having substantially different temps to the touch, then it is worth looking into.

A few things that could be contributing to the imbalance of cooling water flow. Thermostat housing and how the water flows through it on the outbound sides may be favoring the starboard side. the exhaust manifold and/or the exhaust elbow on the port side may be clogged up.

Those are a couple places to start.

 

[JoLin]

Welcome to iboats!

An infrared temp gun (like from Harbor Freight) would quantify the temp difference between the 2 sides. I will say that in my experience with the GM 5.7 and 4.3, the starboard riser always runs a littler hotter than the port, rather than what you're seeing. Pretty sure others here have reported the same.

Like Ted said, engine serial number will help. Is this a fresh water or salt water boat? When were manifolds/risers last changed? Can you hold your hand on both risers when the engine's warmed up or is one too hot to keep your hand there?

 

[alldodge]

Hi folks,

The boat in question is a 1996 Sea Ray with a 4.3L V6 Mercruiser and Alpha 1 drive.

When we run it on the hose, there is barely any water coming out of the port side exhaust. I wasn't sure if this was normal or if something in the cooling system is blocked.

I uploaded a video on youtube so you can see exactly what I'm talking about.

The port side exhaust manifold does get noticeably warmer than the starboard side when I touch them. The temp gauge on the dash doesn't indicate that it is overheating. It usually seems to sit at 160ish so I'm not sure there is a problem or not.

If there are some knowledgeable people on here that wouldn't mind taking a look at that short video then please share your opinions.

Also if someone could point me in the direction of a service manual or something like that for this boat that would be great. All the diagrams I was able to find on line seem to be slightly different to this engine.

Thanks!

Fixed the link to you vid

Agree S/N are the best, until then. I'm leaning toward you not having a problem. One side of the engine will always be a bit warmer then the other, this is due to hydraulics and water flowing to the path of least resistance. If you can put your hand on the manifold and it will not instantly burn you, then IMO you don't have an issue.

 

[WetDog149]

Thanks for the feedback guys. It's much appreciated!

The serial number of the motor is 0F773809.

To answer JoLin's questions,

The boat has almost exclusively been used in salt water, with only a handful of runs in fresh water over the last 18 years. It was always flushed on a hose with fresh water after each use.

The manifolds and risers were replaced in 2002 and then removed and cleaned out in 2010 but not replaced at that point.

When it was running on the hose the other day I could hold my hand either manifold, but it was not really comfortable on the port side.

If that serial number sheds any light on what I should expect or look into then I'd be glad to hear your thoughts.

Thanks!

 

[Fun Times]

The boat has almost exclusively been used in salt water, with only a handful of runs in fresh water over the last 18 years. It was always flushed on a hose with fresh water after each use.

Being the engine/boat is older and ran on the hose for flushing many times before.....Did it use to flow more water out the portside then you see now? or is the boat new to you?

Next time you flush the engine, be sure to rev the engine up to 1300 RPM and see if the water flow evens out a little better.

Also when was the last impeller, impeller housing and impeller gaskets replaced? did you notice a difference since doing any of the impeller changes?

 

[Scott Danforth]

with this being a salt water boat, with the last inspection of the manifolds in 2010, I am willing to bet you need new manifolds and risers. usually 5 years is the life expectancy of cast iron manifolds in salt water.

 

[WetDog149]

Being the engine/boat is older and ran on the hose for flushing many times before.....Did it use to flow more water out the portside then you see now? or is the boat new to you?

Hi Fun Times,

The boat belongs to my parents who say more water used to come out the portside when flushing. They have owned it since it was new. I am inclined to believe them when they say more used to come out, but I'm not sure. On my boat which has a 4 cylinder 3.0 Mercruiser there is noticeably less water that comes out the port side as well so figured that might be a normal thing for these stern drives.

I just want to save them an unnecessary trip to the dealer/bill if there isn't really an issue to be concerned about.

Also when was the last impeller, impeller housing and impeller gaskets replaced? did you notice a difference since doing any of the impeller changes?

The impeller and gaskets were done in 2010 in the same service as they cleaned out the manifolds and risers. Unfortunately I don't know if that had any impact on the water flow as I wasn't around then. I'm just referring to the service records.

Thanks for your input, I'll try upping the revs next time we have it on the hose to see if that increases the flow although I'm pretty sure we had it revving around that point the other day and I couldn't see an observable difference in flow from the port side.

 

[JoLin]

To answer JoLin's questions,

The boat has almost exclusively been used in salt water, with only a handful of runs in fresh water over the last 18 years. It was always flushed on a hose with fresh water after each use.

The manifolds and risers were replaced in 2002 and then removed and cleaned out in 2010 but not replaced at that point.

IMO, it's time for a general overhaul of the cooling system. New manifolds and risers. New thermostat. Pull the t-stat housing and clean out any junk in there. Sounds like you maintain it well, 13 or 14 years is darned good, and those components still have a finite life in salt. Even if they look 'cleanable' again, it's hard to tell how much metal has rusted away. The walls of the castings between the water passages are probably getting pretty thin.

My ;02

 

[Watermann]

The exhaust ports are at the end of the Y pipe after the 2 sides are joined. I'm not sure it's an indicator of anything being wrong having more or less water coming out on a given side.

5 years on a water pump is risky business, time for some cooling system work.