Switching the Cooling Hoses on a 5.0L (228) Mercruiser

[Stamey]

As you may know, the hoses that feed the manifolds on a Mercruiser come from the thermostat housing (hot water from engine), and the hoses that feed the exhaust elbows come from a "bypass" that is part of the thermostat housing but is completely separate from the thermostat water flow, and receive their water flow from the raw water hose off of the water pump (always cold water).
I am wondering what happens if I swap the hoses around, so that the raw water goes into the manifolds and the hot engine water goes into the exhaust elbows. Will that cause problems?

I ask this because I am dealing with an overheat problem that I suspect has something to do with the manifolds having restricted flow. Last year is was really bad, so bad that I blew a split in a manifold hose while doing WOT on the lake. I replaced the elbows with new Aqua Power elbows and the problem has diminished, but the engine still wants to overheat at idle. Once I get to about 1800 RPMs the temp will drop back to 160, if it is above that while idling.
Considering that, I was thinking about swapping the hoses so that the water coming out of the engine goes though the new elbows only, which have no flow restrictions, and let the "bypass", cold water, go through the restricted-flow manifolds.

Now, I replaced the manifolds last night with a good set I bought from a fellow who had to change his exhaust type because of the cam he put into his engine, but I am wondering in case that doesn't work, and theoretically.

Thanks,
Chris

 

[Bondo]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

As you may know, the hoses that feed the manifolds on a Mercruiser come from the thermostat housing (hot water from engine), and the hoses that feed the exhaust elbows come from a "bypass" that is part of the thermostat housing but is completely separate from the thermostat water flow, and receive their water flow from the raw water hose off of the water pump (always cold water).
I am wondering what happens if I swap the hoses around, so that the raw water goes into the manifolds and the hot engine water goes into the exhaust elbows. Will that cause problems?

I ask this because I am dealing with an overheat problem that I suspect has something to do with the manifolds having restricted flow. Last year is was really bad, so bad that I blew a split in a manifold hose while doing WOT on the lake. I replaced the elbows with new Aqua Power elbows and the problem has diminished, but the engine still wants to overheat at idle. Once I get to about 1800 RPMs the temp will drop back to 160, if it is above that while idling.
Considering that, I was thinking about swapping the hoses so that the water coming out of the engine goes though the new elbows only, which have no flow restrictions, and let the "bypass", cold water, go through the restricted-flow manifolds.

Now, I replaced the manifolds last night with a good set I bought from a fellow who had to change his exhaust type because of the cam he put into his engine, but I am wondering in case that doesn't work, and theoretically.

Thanks,
Chris

Ayuh,... Redesigning a Proven cooling system rarely to Never works...
Where as, Fixin' it to stock specs probably Will....

Are the check-balls in good workin' order,..??

 

[Stamey]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

I do not have check balls that I am aware of. When I bought the boat it had a blown head gasket and no thermostat. After I did the head work and installed a new thermostat, and a new impeller, I found out why it likely blew the head gasket, from restriction in the exhaust. As I said, I actually blew the hose off the left manifold because of the water pressure from running WOT. This told me in no uncertain terms that I had restriction in the manifolds and/or elbows.

I never saw any balls in this system. It is a 1983 Chaparral 198XLC with a 305 Chevy. I believe the model to be 228.
When I ran across a deal on brand new elbows I snapped them up and installed them on the engine. this reduced the restriction enough that I no longer overheat when running above idle, but it still heats up at idle. When I ran across the new manifolds over the winter I bought them. When I was trying to tune the freshly rebuilt carb a few days ago, and watched the temp climb into the 230 range, I knew I needed to put the manifolds on, but I got to thinking about it and wondered about the question I posted.
If I let the hot water from the engine go through the elbows that have no restriction and let the cold water form the bypass go through the restricted manifolds, would it cure my problem for the time being.
As I said, I installed the new manifolds last night, and hopefully that fixes the problem, so this is more of a theoretical question now.
I cannot run the engine yet as I am waiting for the new elbows (with drain plugs) that go into the bottom of the manifolds to get here. They should be here Friday.

Thanks,
Chris

 

[Don S]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

Post a picture of your engine so we can see the thermostat housing and the exhaust manifolds and risers.
You may not have the checkballs, but without seeing, it's impossible to say. There are 4 different setups.

 

[Stamey]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

Pics of housing:
View attachment 106292 View attachment 106294

Update: I put the old elbows in so I could fire it up to heat the oil a bit so I could change it, then run it after the oil change. Even though it seems to have great flow out of the through-hull exhaust, it still overheats, even above idle, now. Last year, after replacing the exhaust elbows, it would only overheat if idling for a long time, such as a long no-wake zone. Once I revved above idle the temperature dropped like a rock to 160.
Not sure what to check next.
I have not pulled the water pump off the engine to look at the impeller yet, as from the water flow I have seen, and enough pressure to blow a hose, I am thinking the pump impeller is OK. the lower unit impeller was installed new in June 2010. The thermostat was replaced at the same time I did the head gasket, in the beginning of June 2010.

Thanks,
Chris

 

[Stamey]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

Update:
I pulled the thermostat housing off and pressure washed it, to make sure all passages in it are open. Plenty of rust in there, but I got much of it out with the pressure washer. I installed another new thermostat, just in case the first new one is bad. I am getting great water flow from the through-hull exhaust but still see the temp creeping up when running on muffs in the yard.
I am beginning to think it may be the impeller in the water pump that is mounted on the engine. I have seen the impellers rust away to nothing. Since my thermostat housing does not have any balls in it, and does not appear to be designed to have balls, I'm thinking that only way water gets into the engine is by shear force of the water pump on the front of the engine, and if it is not providing sufficient pressure to force water through the engine that may be my problem.
I plan to run it in the water to see how it acts before I pull the water pump off.

Any other ideas, or things to check will be appreciated.

Thanks,
Chris

 

[LX Kid]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

When I first got my '82 Mercruiser 228 I had the same problems. The closed system cooling had been removed and had heating up problems. If you could post a picture of your risers, hose routing and manifolds would be a big help to those trying to help you. My problem turned out to be the wrong gasket between the riser and manifold as well as the risers being blocked up with rust and water could not flow thru. When was the last time you changed the water impeller in the foot? Maybe the water pump is an automotive pump instead of a marine pump and the impellar has rusted away, like you mentioned. Here is a pic of my setup and was wondering if yours was the same?

 

[Stamey]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

You should see attached pics of my setup in a previous post above.
Mine is different from yours in that where you have 2 sets of bypass outlets on the thermostat housing that are just looped back to each other (I assume this is because of the conversion), mine has only one set of bypass outlets, out of a T on the top of the front of the housing, where the big hose comes in. Those bypass hoses come from the T and go into the front of the exhaust elbows. Yours has a plug in that location.
Through some research I have found that while I have the T, I do not have balls in it, and a new T, going by the catalog PN, 98477A2, and my thermostat housing PN, 87290A4, has some kind of balls in it. See pic below.

I do not know if that could be causing the entire problem, at this point, and hope that the more experienced her can advise on it.

Yes, as much as this boat was abused before I got it, I can believe that someone put the wrong kind of water pump on it. It had an auto starter and fuel pump on it when I got it.

Thanks,
Chris

 

[Don S]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

You should see attached pics of my setup in a previous post above.
Thanks,
Chris

Your picture links of your thermostat housing don't work.

 

[Stamey]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

They work now?

Chris

 

[Don S]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

Still need a picture showing the complete system, like LX kids picture. Then we can see how yours is plumbed.

 

[Stamey]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

Here is the big pic.

Thanks,
Chris

 

[Don S]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

Yours hoses are hooked up as they should be. If you swap the hosea as you suggested in the first post, you will probably burn up all your rubber hoses, flappers, bellows and cooling system parts in the drive before the thermostat opens and allows water to the elbows to cool the exhaust leaving the boat.

You replaced the manifolds, but did check the elbows to see if they are plugged up? Did you use the proper gaskets between the manifolds and the elbows?

 

[45Auto]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

Isn't that the thermostat housing with the T-adapter to the risers that should have the check balls in it?

My 1987 5.7 was overheating badly at idle when the check ball springs crapped out. The balls weren't seating in the fitting. With too little tension on the springs too much water flows through the risers and not enough through the engine. With the springs stretched so the balls were pressed tightly into the fitting it idles all day at 130 degrees now.

 

[Don S]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

Isn't that the thermostat housing with the T-adapter to the risers that should have the check balls in it?

His model doesn't have the check balls, they didn't come out 'till later (87) and then on a different type housing.

 

[Stamey]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

The elbows are brand new, as of July 2010, and the gaskets are correct, as far as I know. They have slots in both sides and a little weep hole in the front and back. Pouring through the catalogs it appears that this is the correct gasket since I do not have risers in there.
As post number 16 states, I am now thinking that I need the balls in my T. The reason I think this is because when I found the thermostat housing that look like mine I saw that the T that came with it has balls in it. Now, if I go by year and model, on Crowley Marine, it looks like I am supposed to have a completely different housing, so I had to look at a different year to find my housing. My thinking is if my housing is not the correct one for the year of my engine, then perhaps I ned the complete housing (balls too) in order for it to work correctly.

Thanks,
Chris

 

[Don S]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

It is a 1983 Chaparral 198XLC with a 305 Chevy. I believe the model to be 228.

I have no clue what you looked at on the Crowley site, but obviously not the correct one. Here is a picture from the OEM parts program for 82-84 (Look in the upper left for the years) 228 engine. Note that there are no check balls, and it's the same housing as you have.

Lets move up to 85-86 models of the 228, still the same thing as you have. No check balls.

Only if I go to the 87 model with the Design II do you find check balls and a different kind of housing. Designs I and III do not have check balls.
Even with Design II, it came with and without the check balls.

I did look at the crowley site, and they do have 4 models listed. (All the same number mind you) the last picture is from the wrong year. It should bbe in the 79-82 catalog for the 228.

 

[Stamey]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

When I looked at number 13, in the first and second diagrams you posted, it is PN 98477A2, and the picture of the part on Crowley Marine shows balls in the T. Perhaps the diagram wasn't as detailed in that era or the part was superseded to have the balls in it.
It does match up though, as my SN is 6372382.

If that isn't my problem, where should I go from here?

Thanks,
Chris

 

[achris]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

Crowley Marine is an after market supplier. The diagrams Don has shown you are straight from the Mercury Marine parts catalogue. Which one are you going to believe? If everything on the engine is right and it still overheats, then maybe you have a problem elsewhere. Get yourself a length of clear hose of the same size as the one that runs from the power steering cooler to the thermostat housing (that would be the inlet hose), and run the engine, in the water, not on flushers, and ensure you have a solid stream of water (No bubbles). If that checks out then check the output of the leg water pump. At exactly 1000rpm for exactly 15 seconds the pump should deliver (for a 1.5:1 drive ratio) a minimum of 4 qts. The test needs to be done 4 times to ensure repeatability....

Do you have a service manual? It should be manual #9. (clymer and seloc don't count as manuals, more as hand towels)

Cheers,

Chris.....

 

[LX Kid]

Re: Switching the Cooling Hoses on a 5.0L (228) Mercruiser

I just thought of something else that happens "occasionally." Sometimes the various hoses, when they heat up, the inside of the hose fails and creates a big bubble that closes off the water flow. Rare but happens on old hoses. Here is an illustration of my "exhaust" hoses that failed. I've seen the water pump hose fail on cars the same way.