Engine Overheat After Haulout

[Hhew]

Folks, looking for some insight. Yesterday we did a sea trial and survey haulout on a Bene 42CC (Volvo D2-55) that I am buying. After re-splash, engine started normally and the captain confirmed that exhaust was pumping water. A few minutes underway, we got an overheat alarm and I got the headsail out and shut the engine down. Capt and surveyor checked things out and discovered that we damaged the impeller - luckily we had a spare and they did a quick swap. Engine restarted and ran normally afterwards. The hypothesis is that during the haul, we got air into the raw water system and should have "burped" the strainer.
Questions for the group:
1. Is this a common phenomenon after haulout?
2. As a future procedure, how quickly after starting should I burp the strainer? Is this written up anywhere or is it just tribal knowledge?
3. Should I be suspicious of anything in the raw water intake system?
Thanks in advance for not turning this into a debate on the merits of Benes or Volvos.

[mlydon]

It probably wasn’t actually moving water when he checked, just blowing out the last of what was in the muffler. Pulling the boat caused the raw water intake to lose prime, and you burnt up the propeller from running dry.
Very common, and you should ‘burp’ it on splash, BEFORE starting the engine.
Strainers draw water from the top - if there’s air in there, and the impeller is old, good possibility it won’t self-prime, thus burning up.
Make sure the strainer is at a height where it will fill just by removing the cover plate - I had a cape dory 28 where the strainer was located too high - would lose prime sailing in moderate waves, when the intake was uncovered from heeling - royal pain to prime that sucker......had to close the sea pck, fill the strainer with water, seal it up, start the motor and immediately open the sea cock.


Matt

[bensolomon]

Just had this problem yesterday after getting my boat back in the water. Probably going to replace the thermostat and mixing elbow, now, too, as a result. I even had a new impeller placed prior to running. Oh, well. Live and learn.

[TheOffice]

Had to burp my Vetus every haulout. Just loosened the screws on the pump. Eventually pumps seals were bad.

[Coolerking]

This is the most common thing I see in my world, airlocks. easy fix...close the intake before you haul out, open when you are back in the water.

[brmoney]

All good advice above. As a preventive measure we always close the seacocks prior to haulout to preserve the prime.

[AJ_n_Audrey]

Not familiar with your engine, but another possible solution is to lubricate the impeller with Dawn dishwashing liquid before re-start, assuming it's easy to get to. I do this with new impellers on my Westerbeke 40 and have never had an issue. The Dawn lubricates the impeller until water reaches the water pump.

[billgewater]

A good idea is to install a bleeder valve; after and higher than the intake filter to allow "burping". Connect, via a small valve, a clear half inch hose that is arranged vertically and has its hose top higher than your outside LWL. To bleed or burp the system, you just slowly open the valve and watch the water enter, flood the system and rise up in the clear tube stopping when at the LWL. This does require that the filter is actually below the LWL. Also the impeller pump must be after the filter, not before it. Don't forget to then close the small valve to prevent the impeller pump from sucking in air via the clear hose!

The hose can be used for at least two other applications.
The first one is that if you spend a long time at a jetty, you can connect the local fresh water supply to the hose top (after you have also opened the skin fitting valve to prevent over pressurizing the system). Run the engine and then after the engine has been fresh water flushed (taste the exhaust water) turn off the engine and let the fresh water run for a minute or so. This will reduce salt water corrosion and organic build up in the system plus it can be used to "back flush" and clean the intake filter.

The second advantage is that by opening the skin fitting valve and the clear half inch hose valve and blowing lung powered air down the half inch hose, you can remove all the water from the system down to the open intake skin fitting valve (which is then closed while air is bubbling out). Helpful for doing maintenance on the filter hoses etc. or even the intake impeller.
It's all pretty simple and I have had a number of other boaties copy it.