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Help with cooling system

dfp51

.
Jun 26, 2019
42
O'Day 28 Lorain, Ohio
I am at my wit’s end. I have an O’Day 28 with the Universal M12. When the boat went in this year, I stopped getting cooling water out of my exhaust. There was a crack in the housing of the raw water strainer, so I replaced that. That didn’t change anything, so I replaced the impeller on the raw water pump, and the sealing gasket. I am getting water flowing through the impeller and into the heat exchanger. I can hear water gurgling in the exhaust, but very little is coming out of the exhaust portal. The engine will run for twenty minutes or more before the temp gets very high, so there has to be some water getting through, but it seems like something is obstructing the flow.

Does any one have any idea what should be next on the trouble shooting list?
 
Mar 5, 2009
57
Hunter 410 Penetang
Check the hose between the strainer and the water pump. I had seaweed get past the strainer and it reduced the water flow and caused temperature issues. I did everything thermostat impeller changed coolant, until I pulled the hose out and tried to look down it. Sometimes it’s the simplest thing
 

dfp51

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Jun 26, 2019
42
O'Day 28 Lorain, Ohio
@SecondWind, I have checked all the hoses from the sea cock to the raw water pump. I have also pulled the discharge hose off the water pump and am getting good flow of water all the way to that point at least.

@Don S/V ILLusion, I haven’t checked either yet. Was really hoping not to have to take the heat exchanger off, because it really looks like a true pain in the you know wha. But I am afraid that is going to have to be next
 
May 24, 2004
6,769
CC 30 South Florida
When you replaced the impeller what was the condition of the old one? Sometimes vanes and pieces break off and they will lodge themselves along the passages and partially block flow. Other than that track flow from the intake port to the muffler. Follow the different components and remove the connecting hoses after each one until you find a diminished flow. The common culprits will be hoses, the heat exchangerand and mixing elbow.
 
May 17, 2004
3,434
Beneteau Oceanis 37 LE Havre de Grace
+1 for checking the heat exchanger. You don’t need to remove it. There should be an end cap that you can reach from the quarter berth. Take that off and you’ll likely find lost impeller vanes, seaweed, etc.

Universals don’t have chronic issues with the exhaust elbow. Their design is different and doesn’t seem especially prone to clogging. Definitely check the heat exchanger first.
 
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Aug 11, 2011
650
O'day 30 313 Georgetown MD
When checking your heat ex changer, check your pencil anode. when this starts to collapse, it disintegrates in chunks that will stop flow.
 
Jul 5, 2011
598
Oday 28 Madison, CT
+1 for checking the heat exchanger. You don’t need to remove it. There should be an end cap that you can reach from the quarter berth. Take that off and you’ll likely find lost impeller vanes, seaweed, etc.

Universals don’t have chronic issues with the exhaust elbow. Their design is different and doesn’t seem especially prone to clogging. Definitely check the heat exchanger first.
I second this and if you finally have to replace the heat exchanger, it is not at all hard. Secured by two large hose clamps around the belly and other than that just the hose connections. I replaced mine some years ago and it was really easy. I bought an upgraded one with nickel content (Mr. Cool Marine Products) and it also had a larger anode than the stock unit. Fit right in using same clamps even. But by all means as Davidasailor stated first thing is to pull that end cap from at the quarter berth end. When you pull that end cap there is a very thin rubber o-ring that seals. Be careful with that, gently clean, maybe add a bit of lube to it so it will seal up again, otherwise replace. I think caps with seals can be bought by themselves or used to be so.
 
Jul 5, 2011
598
Oday 28 Madison, CT
By the way, one of the not no nice things about my stock HE was that only one end had a removable cap. You can take your HE out and get it reamed if necessary by a shop that does that, but I went for a new one; cost a bit more but i got a lot more for the $ than with a clean out.
 
Jul 5, 2011
598
Oday 28 Madison, CT
And you say you checked after the water pump. Which hose end did you remove? The pump end or HE end? If only pump end, hose could easily be clogged, so that needs to be checked and blown out as well as the HE end cap removed as already discussed.
 

dfp51

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Jun 26, 2019
42
O'Day 28 Lorain, Ohio
Ok, so I pulled the heat exchanger today. You guys were right, not that difficult. I first pulled the end cap, and there was no obvious debris. So I pulled the whole thing out. Very little water came out of the HE, but plenty of anti freeze. The pencil anode was completely eroded, but I didn’t find any zinc chunks either. Water eeems to flow freely through the HE in my utility tub.

So I have now removed every hose/device from the raw water valve to where the raw water line leaves the HE and tees into the exhaust. I have found no obvious blockages.

Anybody have any other ideas? I am about to admit defeat and call a mechanic.
Save me from such a terrible fate, lol.
 
Aug 11, 2011
650
O'day 30 313 Georgetown MD
If I understand correctly, from the raw water intake to the hose leading to the T, everything is flowing? I would continue to travel down the system checking the exhaust U pipe, exhaust box and the exhaust hose. Old exhaust hose interior walls can collapse and cause restriction.
And thinking that you had the boat on the hard last season, maybe some animal made a nest in the exhaust! Did you cap the outlet during storage?
 
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Likes: odaydokay
Jul 5, 2011
598
Oday 28 Madison, CT
+1 to Twodzusfitting's comments. Keep looking down stream. You had already checked the anti-freeze level early on, and it was filled properly?

Not sure the bathtub test is valid for an HE. Others may have a view on that. (My HE worked but gave me an operating temp of 195 degrees, so I replaced it, as noted in earlier post.) You say all the hoses look ok...you reamed them all with something or blew through them after removing them???
 

dfp51

.
Jun 26, 2019
42
O'Day 28 Lorain, Ohio
I blew through each hose & them looked thru them. Interesting about the HE. I ran water thru it, and ran a thin probe they each channel. To be frank I expected to see chunks of zinc in it, because the anode was completely gone when I pulled it out. But alas there was no visible debris. The only thing I haven’t checked is the anti siphon valve. I guess that is next.

I really, really don’t want to have to take the exhaust apart. But it appears that is where I am heading.
 
Jul 5, 2011
598
Oday 28 Madison, CT
You might want to talk to someone about that HE, i.e. can water run through ok and it still not do its job? A radiator shop might be able to tell you. Of course you are right about checking downstream of there also, but I would not assume that HE is doing its job ok just yet.
 

RitSim

.
Jan 29, 2018
238
Beneteau 411 Branford
The heat exchanger can be cleaned by dipping in Muriatic acid or having a shop do it. You could measure the water flow before the heat exchanger and connect the hose and measure after. I did have the inner wall of my exhaust hose collapse because it over heated. Since you may have had interrupted water flow, that could also be a blockage.
 
Jun 11, 2004
1,204
Oday 31 Redondo Beach
I blew through each hose & them looked thru them. Interesting about the HE. I ran water thru it, and ran a thin probe they each channel. To be frank I expected to see chunks of zinc in it, because the anode was completely gone when I pulled it out. But alas there was no visible debris. The only thing I haven’t checked is the anti siphon valve. I guess that is next.

I really, really don’t want to have to take the exhaust apart. But it appears that is where I am heading.
At the risk of suggesting something that you have already done:
Short of removing the exhaust system, have you removed the end of the hose that runs from the HX to the fitting that enters the exhaust, at the exhaust pipe? I don't know what you have for that interface because they vary but I assume there is a water hose fitting that is either screwed or welded into the exhaust pipe. I haven't seen that you have removed the hose at that point and seen if you can stick a dowel or other implement into that fitting to see that it is well open and clear to the exhaust pipe. If not, maybe you can try reaming it out. Being able to blow through it might not mean that there is enough clearance for good water flow.

Just a thought.
 
Jul 5, 2011
598
Oday 28 Madison, CT
I agree with Richard here. And in general a blow through test is also probably not good enough. I am also still suspicious of the HE. These things do not last 30 years normally, at least not in salt water. probably better in fresh water, but 35 years, I don't know about that one.
 
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dfp51

.
Jun 26, 2019
42
O'Day 28 Lorain, Ohio
I am going to replace all of the hose from the sea cock to the exhaust. It looks decent, but it is not that expensive and I have already spent considerable time mucking about with this. Will also replace the valve in the vented loop in the system. Not quite ready to pull the trigger on a new HE, especially since I have already purchased a new end cap and gasket. So the plan is to put the HE back together and see if there are obvious flow issues when running water through it. If not, I will probably re install and see if there was some non obvious problem that was corrected by the tear down/hose replacement. If that doesn't work, then it is either a new HE or start ripping the exhaust apart.
 
Jul 5, 2011
598
Oday 28 Madison, CT
Has a bad thermostat been ruled out, also low coolant level??? Regarding the latter, you will need to top off, run engine and top off again having pulled the HE. You probably know that, but just saying........