M25XP cooling

[Don P]

Recently bought a Catalina 34 (1988) and on two seperate occasions have had a cooling problem. After motoring out of our marina, about 45 min., we shut the engine down with no incidence. After sailing for the day when we start the motor back up there is no raw water at the impeller, and the engine starts to overheat. After determining that there is no obstructions I manually prime the impeller and off we go with no problems. I have noticed that the hose from the thru hull to the impeller has a loop that goes well above the water line. Is this necessary? Could this cause the line to drain while not in use? Impeller has been recently replaced so I don't think its the cause. Any reason the hose can't be run straight uphill to the pump?
Thanks in advance for any help.
         Don P.
                #534

[Jim Price]

I have M25XP in a 1991 and my raw water line runs straight up from seacock to strainer and then on to engine.  Line runs up bulkhed under head sink and around to engine at that level (best I remember).  No high loop though.  I have never had to prime the pump / line.  I can "re-look" at configuration this weekend as I tend to go suffer from senioritis now days.  At least I still know where the boat is located.....

[Ben Hocker]

That high loop of line from the through-hull to the pump could be the problem.  I experienced a similar, intermittent problem on my previous Columbia 9.6 Meter:  It had a long line from through-hull, up and around some cabinetry, back down to the raw water pump on the engine.  After sailing and then restarting the engine, sometimes no water would get through the engine.  I can't explain the physics, but I drilled a hole, routed a much shorter line directly from through-hull to water pump, and the problem disappeared.

[lazybones]

When we first purchased our Catalina we experienced a similiar situation to yours, after a brisk sail the raw water pump would starve and we would have to disconnect the hoses to reprime the pump.  Catalina sent engine techs to the boat a half dozen times.  They checked and double checked everything, and finally even replaced the hoses and pump. Everything they tried had no effect.  I finally rerouted the hose from strainer to the pump so that it stayed below the water line and never experienced another problem with the pump.  I have always "assumed" that this was the cause of my problems?

[art]

xmodlaw@aol.com

[art]

Hello, all.  I’ve removed, flushed, and reinstalled the heat exchanger on my 1988 C34 and am ready to refill the system with coolant, open the raw water intake, and â€" gulp -- start the engine.  Is there anything I should know before I do this?  

Must I remove the four corrosion-seized screws on the face plate to the water pump and lubricate the impeller to avoid damage before water gets to it?  

How likely is it that I’ll have to “bleed” air from the coolant system?  If so, do I just turn that funky looking little wingnut-shaped valve with pliers?

Does it matter whether I use distilled, purified, or just plain old city water to mix 50/50 with the antifreeze?

Anything else I should do while the system is dry?  

Thanks,

Art Levine
Gusty Lady
xmodlaw@aol.com

[Ken Juul]

Make sure the loop to the water heater is full.  The easiest way is to remove both hoses at the engine and pour the 50/50 mixture in one side until it comes our the other.  If the water heater loop is not full, you may end up with a "vapor lock" at the pump causing the engine to overheat.  Opening the bleeder screw while you pour coolant into the tank will allow most of the air to escape.   You can leave it open on initial start up to get the rest.  Make sure it is closed before the thermostat opens our you will get a gusher of hot water.  If any hoses are questionalble, now would be the time to replace them.

[Buddy]

Don,
The loop you are talking about is a vented loop that is a safety measure to keep a thru hull from syphoning water and flooding the boat. The loop has to be above the waterline to work. It has a valve in the top of the loop and that may be defective allowing air into the line. As Ron said your problem is air leaking into the line. Check the vented loop and all couplings.....when you stop the air leak you won't have any more problems.

Buddy

[art]

Thanks.  I didn't think about opening the bleeder during filling.  My boat doesn't have an engine-connected water heater...it has a propane flash heater in the head.

No need to lubricate the impeller before start up??

Art


<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Ken & Vicki Juul   #1090  "Luna Loca":
Make sure the loop to the water heater is full.  The easiest way is to remove both hoses at the engine and pour the 50/50 mixture in one side until it comes our the other.  If the water heater loop is not full, you may end up with a "vapor lock" at the pump causing the engine to overheat.  Opening the bleeder screw while you pour coolant into the tank will allow most of the air to escape.   You can leave it open on initial start up to get the rest.  Make sure it is closed before the thermostat opens our you will get a gusher of hot water.  If any hoses are questionalble, now would be the time to replace them.<HR></BLOCKQUOTE>