Safety procedure after melted impeller on 2GM?

[stuendan]

As the originator of this topic, I thought I should respond to some helpful advice posted above.

1. On some Hunters, the exhaust outlet is under the stern - there is no way, except for the slightly different sound to know if the cooling water flow is good!
2. I'm pretty sure it is best practice to close the sea water inlet valve (and all other sea cocks) before leaving the marina - saves the embarrassment of returning to the marina to see only the mast visible.

I think the raw water flow gauge is the best solution (especially with a flow rate readout plus alarm)

FYI, I just got caught out again after a haul out! I hadn't bothered to close the intake valve so all the raw water drained out, and my old pump couldn't get going again, until I pulled the hose at the pump intake to fill it, then checked for flow up to exhaust elbow. Still not confident as the blockage could have been at the elbow but I motored off again but she sounded ok and the temperature gauge was happy now!

 

[Dalliance]

This is a 2GM, raw water cooled with no heat exchanger.

I have the same engine with possibly one difference. Yanmar 2GM raw water cooled, but with a very loud temperature alarm & warning light at the engine control panel. Careful as I try to be, it has saved me from destroying an impeller blade and potentially damaging my engine a couple times. You made no mention of an alarm, so you either don’t have one, or possibly you have one that isn’t working(?). It’s definitely worth having. The flow detector is an interesting idea too as an early warning.

 

[Dean Strong]

2GM20F is common in 80s-90s sailboats, unlike previous post.

Simple solution...hang the ignition key on the raw water intake valve handled. Done it for 20 years, never forgotten to open he seacock.

 

[Tally Ho]

I can hear a different tone in my exhaust when I forget to open the cooling water thu hull. Also, all I have to do is look at the stern to see water coming out (or lack thereof).

My Hunter 280 exhaust exited under the water, so a bit harder to see, but I could still hear a difference in the sound.

Greg

 

[JoeWhite]

My solution: I installed a magnet inside the through hull valve handle and a magnetic switch caulked to the hull near the handle when the valve is closed. This position closes the circuit. When ignition switch is turned on if the handle is in the closed position, the soanalert and flashing LED located at the capitan's console warns the operator.

 

[Dalliance]

2GM20F is common in 80s-90s sailboats, unlike previous post.

Simple solution...hang the ignition key on the raw water intake valve handled. Done it for 20 years, never forgotten to open he seacock.

I also close the seacock and hang the key on the lever. When I start the engine, I routinely step onto the dock, bend down and look to confirm that water is discharging from the exhaust. The discharge is below the stern; not through the transom, so a bit out of sight. It does make a slightly different sound if there is no water discharge, but for me, visual confirmation is best.

 

[MikeHoncho]

Mine has a “pee” hole out the stern that comes off the raw water discharge before it connects to the down pipe. Makes it quick and easy to confirm it’s pumping. I did get fooled once when the pee hole was shooting out really far and the exhaust sounded loud. The elbow that threads into the down pipe got clogged with scale and didn’t allow water to the exhaust and forced it out the pee hole. Took me a second of looking at it wondering why is was coming out at such a higher velocity.

 

[Scott T-Bird]

My solution: I installed a magnet inside the through hull valve handle and a magnetic switch caulked to the hull near the handle when the valve is closed. This position closes the circuit. When ignition switch is turned on if the handle is in the closed position, the soanalert and flashing LED located at the capitan's console warns the operator.

I'm always amazed at the ingenius ways we go about solving these problems, yet, I'm also not understanding why it is necessary in this circumstance. Knowing whether or not the intake is open is, like, the first thing on my mind when I am about to turn the key. It's an automatic thought that springs without fail. Then, once the engine kicks on, it's a knee-jerk reaction to look overboard for the exhaust. It makes me wonder how any experienced operator doesn't have the same automatic reactions.

I agree that when the exhaust exits under the topsides, it can be a problem. When I'm in my slip or on anchor, it's easy enough to tell when the exhaust, which exits a few inches above the WL, is strong because it splashes the surface of the water under the hull. But underway, the boat squats and the exhaust is below WL. I've learned that I can tell by sound very obviously when flow is completely blocked. But it's not so obvious when flow is merely weakened. That's where the flow detector, hopefully, is effective.

 

[JoeWhite]

I'm always amazed at the ingenius ways we go about solving these problems, yet, I'm also not understanding why it is necessary in this circumstance. Knowing whether or not the intake is open is, like, the first thing on my mind when I am about to turn the key. It's an automatic thought that springs without fail. Then, once the engine kicks on, it's a knee-jerk reaction to look overboard for the exhaust. It makes me wonder how any experienced operator doesn't have the same automatic reactions.

I agree that when the exhaust exits under the topsides, it can be a problem. When I'm in my slip or on anchor, it's easy enough to tell when the exhaust, which exits a few inches above the WL, is strong because it splashes the surface of the water under the hull. But underway, the boat squats and the exhaust is below WL. I've learned that I can tell by sound very obviously when flow is completely blocked. But it's not so obvious when flow is merely weakened. That's where the flow detector, hopefully, is effective.

The idea behind the magnetic switch is that it provides warning before the engine is turned on. This will save the impeller from running dry. In any other case the condition is confirmed after the engine is already running which may damage the impeller.

 

[Scott T-Bird]

The idea behind the magnetic switch is that it provides warning before the engine is turned on. This will save the impeller from running dry. In any other case the condition is confirmed after the engine is already running which may damage the impeller.

No, I get it and I absolutely love the solution! I'm just saying that my mind is really the warning system and the magnetic switch is a redundant warning, but then, redundancy is good!

 

[kappykaplan]

Then, once the engine kicks on, it's a knee-jerk reaction to look overboard for the exhaust.