Onan Generator 11.5kw

[Brad Fausett]

11.5MDKAW-2323
2004 Boat build

I am just arriving back from another amazing weekend trip, About 30 minutes out from our home marina a guest asked if we could fire the generator to recharge some phones. I happily fired her up and it ran until we arrived at our dock. I began closing up the bridge and when I flipped off all the lights I noticed a red glow from under the dash. I don’t recall a light being down there, I look under the dash and find one of the bilge pump auto lights was lit up. It had fallen out of the holder in the dash.

That’s odd, why would it be on unless we have taken on water. As I head down the bridge stairs I notice a lot of steam coming from the generator. I immediately shut down the generator, as I go to hit the kill switch i notice the temperature gauge is pegged to the right in the hot zone. I lift the floor hatch and to my suprise I am full of water. Water is pouring out from the generator. i hop in and yank the cover to find the output hose from the impeller just after the sensor has broken the hose clamp and the hose has blown off.

My question is why did the generator not shut off when it reached the high temperatures? A few weeks back the impeller went, it shut down due to no water flow. The hose that broke the clamp is directly after what i believe to be the water flow sensor. Is there not a separate high temp exhaust sensor? What’s the chances I have seriously damaged the motor of the generator? Looking at the level of water in the boat the generator ran for awhile with no water. Should i file a insurance claim on the generator, anything to be concerned with other then replacing the clamp? I am afraid it has been significantly damaged internally. However it was running upon shut down.

Fortunately the water level did not reach the bottom of the main engine oil pans, that could have been disastrous.

I highly advise everyone to check your hose clamps, double all of them up if possible. I have never experienced a hose clamp snapping but I now know it is possible.

Any insight with the sensors and where they are located. I would think there would be something monitoring the exhaust temperatures.

As you can see, the boat is 46′ length and 14’4 width. I would bet there was 14-20″ of depth of water. All was shut down and allowed the bilge pumps to catch up and pump it all out.

Topic

[firehoser75]

Brad,
In your hose separation, the raw water flow sensor would still have sensed flow, as the hose separated downstream of the sensor. While you are looking at your gen set, change out the fore mentioned flow sensor as it shows signs of corrosion. On mine, it literally fell off as the body was so corroded. Luckily this happened while I was doing maintenance last winter.
As Rob stated, you still should have had 2 alarms (sources of shutdown) being the coolant overtemp and exhaust overtemp. Severe overheats can cause engine damage, so a careful check of your entire setup is probably in order.
Good luck,
Tom

[sherlywang]

high temperature

Technically, there should be high temperature alarm when it reaches high level. Did you check the coolant? With the sudden rise of temperature in summer, diesel generator is forced to shut down because of the high water temperature in the operating, so it is forced to stop because of the high temperature alarm of the unit.

[Rob Schepis]

Quite possibly the hose clamp was over-tightened and fatigued.

Could the heat-ex or wet elbow be partially clogged causing back pressure on the seawater side?

Did the gen engine push out any coolant?

Gen should have two shutdowns that should have come into play here: High exhaust temp and High coolant temp.

Were you running on plane (or bow up) when the gen was dumping water in the bilge? If so, do you have an aft pump? And what about high water bilge alarms?

[Author]

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