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M15 engine is overheating

Sep 15, 2021
15
Catalina 30 30 san diego
I recently replaced the engine water pump and first time I took it out I noticed that before even getting out of the marina I was already pegged out on my engine temp gauge. Any advice on best course of action to troubleshoot this?

Side note: I did take the lines briefly off the new water pump and it is having normal flow of water out the pump.
 

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Feb 26, 2004
21,899
Catalina 34 224 Maple Bay, BC, Canada
Are you sure it was primed? i.e., it had water "at" it? Those Oberdorfers are pretty reliable.
 
Sep 15, 2021
15
Catalina 30 30 san diego
Stu, as I mentioned I did take the line off that is down stream from the pump and water we flowing out the line when the engine cranked.

I didn’t think the pump needed to be primed, can you provide any detail on doing this?

-Jon
 

dmax

.
Jul 29, 2018
465
O'Day 35 Buzzards Bay
Was water coming out of your exhaust? If not, it's something downstream from the pump preventing flow. If a good amount is coming out of the exhaust then start looking at the engine's cooling system - make sure the anti-freeze is flowing correctly.
 
Feb 21, 2013
3,611
Hunter 46 Point Richmond, CA
Universal M15 operator manual attached for reference. Assuming you have good water flow on the seawater side, suggest checking the fresh water side for:

1. Adequate coolant
2. Coolant is good
3. Thermostat is opening
4. Heat exchanger is not blocked or fouled and if so, might require cleaning Autopsy A Westerbeke / Universal Marine Heat Exchanger Photo Gallery by Compass Marine How To at pbase.com
5. No air lock (often you'll find an air bubble trapped in the circuit for the engine water heater after a boat has been winterized) to address this remove both hoses going to the water heater from the theromstat and add fresh coolant through a funnel into one of the hoses until coolant is running out the other hose then reattach them and open the air bleed at the top of the engine
6. Check the fresh water coolant pump
7. Check the belt is tight
 

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Jun 20, 2021
17
Catalina 30 Arkansas River
The M15 Universal 5411 in my Catalina 30 is raw water cooled (no fresh water side or heat exchanger). The engine sits below the waterline and doesn't need primed. Also, it's designed to recirculate the water in the engine until the thermostat opens. The only water that enters the wet exhaust system (until the thermostat opens) is from two 1/8" bypass holes in the thermostat flange. Very, very little water comes out the exhaust until the engine reaches operating temperature of 143F and then only in pulses, a few ounces every several seconds.
Why was the old pump replaced? If the impeller came apart (as mine did) you'll have to find the rubber vanes that are blocking coolant passages. I found several: in the water pump outlet (you've changed that), the first 90 degree fitting where cooling water enters the engine from the pump and I also checked the thermostat housing.
Your thermostat might be bad. I assume you opened the seacock since you had good flow from the pump hose but the system is designed to recirculate the cooling water inside the engine until the thermostat opens.
I have recent thread that explains how the system operates that may shed some light.
 
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Sep 15, 2021
15
Catalina 30 30 san diego
The bottom of my pump was starting to corrode and causing a small leak at the gasket. I decided to replace the whole pump. I started to do a rebuild but the lip seals inside were completely seized and could not get out so therefore I just did the whole pump. Here is a picture of the old pump and you can see where it was leaking from the corrosion.

From everything I could tell the impeller inside the old pump was fine and did not come apart.

Have you ever tried doing a flush using rydlyme? I watched a few videos on how to do it and it seems pretty simple maybe I could help clean out the system.

I will attach a picture of the thermostat, it is pretty old and looks possibly original. If the thermostat is bad with that cause it to overheat though?
 

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Sep 15, 2021
15
Catalina 30 30 san diego
Universal M15 operator manual attached for reference. Assuming you have good water flow on the seawater side, suggest checking the fresh water side for:

1. Adequate coolant
2. Coolant is good
3. Thermostat is opening
4. Heat exchanger is not blocked or fouled and if so, might require cleaning Autopsy A Westerbeke / Universal Marine Heat Exchanger Photo Gallery by Compass Marine How To at pbase.com
5. No air lock (often you'll find an air bubble trapped in the circuit for the engine water heater after a boat has been winterized) to address this remove both hoses going to the water heater from the theromstat and add fresh coolant through a funnel into one of the hoses until coolant is running out the other hose then reattach them and open the air bleed at the top of the engine
6. Check the fresh water coolant pump
7. Check the belt is tight
 
Sep 15, 2021
15
Catalina 30 30 san diego
Universal M15 operator manual attached for reference. Assuming you have good water flow on the seawater side, suggest checking the fresh water side for:

1. Adequate coolant
2. Coolant is good
3. Thermostat is opening
4. Heat exchanger is not blocked or fouled and if so, might require cleaning Autopsy A Westerbeke / Universal Marine Heat Exchanger Photo Gallery by Compass Marine How To at pbase.com
5. No air lock (often you'll find an air bubble trapped in the circuit for the engine water heater after a boat has been winterized) to address this remove both hoses going to the water heater from the theromstat and add fresh coolant through a funnel into one of the hoses until coolant is running out the other hose then reattach them and open the air bleed at the top of the engine
6. Check the fresh water coolant pump
7. Check the belt is tight
The M 15 did not have fresh water cooling though. Mine only has well water cooling from the Seaside.
 
Sep 15, 2021
15
Catalina 30 30 san diego
Was water coming out of your exhaust? If not, it's something downstream from the pump preventing flow. If a good amount is coming out of the exhaust then start looking at the engine's cooling system - make sure the anti-freeze is flowing correctly.
no antifreeze this is a raw water cooling system. the M 15 did not have a fresh water cooling system
 
Jun 20, 2021
17
Catalina 30 Arkansas River
Have you ever tried doing a flush using rydlyme?
I have not.

If the thermostat is bad with that cause it to overheat though?
Absolutely could, if it were stuck closed and not stuck open. I removed mine while the engine was above 143F. The thermostat was open. As it cooled it slowly closed. As it should. Or, you can test it in a pot of water with a thermometer.

If the engine wasn't overheating until you changed the pump, concentrate on what was changed or altered. The odds of a second coincidental failure are slim.
 
Oct 22, 2014
15,834
CAL 35 Cruiser moored EVERETT WA
Sep 15, 2021
15
Catalina 30 30 san diego
My only problem is I’m not 100% confident that it was or was not overheating prior to changing the pump. I’ve just recently bought the boat and sealed it to where I have it now and don’t recall if it was overheating or not.

My main reason for changing the pump again was the corrosion which was causing a small hole on the gear housing which was causing an oil leak.

As you can see in the picture the thermostat housing is pretty old I’ll have to do some research on seeing what I’m supposed to takeoff and check if it’s opening or closing. I guess first step would be just pinch off the return line and see if that helps the engine cool, if the engine does cool that I know my thermostat is probably bad.
 
Jun 20, 2021
17
Catalina 30 Arkansas River
I will attach a picture of the thermostat, it is pretty old and looks possibly original.
That's actually the thermostat housing. The thermostat could be new or look even worse.
How long have you owned the boat?
 
Sep 15, 2021
15
Catalina 30 30 san diego
You can do a back and forward flush with hose water. No chemical harm will come. Inspect what comes out with the flush. It may give you clues as to the issue. I would check the function of the thermostat. Easy to do in a pot of hot water. The thermostat should fully open at engine operating temps. 135-150.

The M15 is a raw water cooled engine.
Where would you hook up your hose pipe to do the flush in each direction? I’ve heard of people using Rylyme to flush out abs remove the salt build up.
Also how exactly do you remove the thermostat from the housing while the engine is running? Here’s a picture of my thermostat.
 

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Sep 15, 2021
15
Catalina 30 30 san diego
That's actually the thermostat housing. The thermostat could be new or look even worse.
How long have you owned the boat?
i’ve had the boat now for about a month. I’m pretty sure this is the original thermostat but who knows. The previous owner did not do any of the preventative maintenance and there was a lot of deferred stuff That I’m catching up on now.
 
Jun 20, 2021
17
Catalina 30 Arkansas River
I guess first step would be just pinch off the return line and see if that helps the engine cool
If the thermostat is stuck closed, this won't help. But it's a good place to start.

I'd remove the impeller cover off the old pump and see if it's missing any vanes.
 
Sep 15, 2021
15
Catalina 30 30 san diego
Awe I see yeah just pinch it off won’t do anything, How exactly do you remove the thermostat then inside that housing? I can’t find any related information on how to do that. Once I remove it how exactly do you test it?


I completely removed all of the internal pieces of the old pump because originally I was going to try to rebuild it. The impeller was 100% fully intact
 
Jun 20, 2021
17
Catalina 30 Arkansas River
Also how exactly do you remove the thermostat from the housing while the engine is running?
Let the engine get above operating temp. About 160F. Turn the engine off. Remove the 2 screws from the thermostat housing. The old thermostat may be a little stuck but it just sits in the housing. Use a pair of pliers to pull it out, it'll be warm. It should be open and then close within a few minutes as it cools in the air.
 
Jun 20, 2021
17
Catalina 30 Arkansas River
Once I remove it how exactly do you test it?
To properly test it. Warm it in a pot of water on the stove top. Using a thermometer, it should open as the water reaches it's designed temperature (about 143F for the M15 raw water cooled) and close as the water cools below this temperature.
 
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