450: Pencil zinc removal in Onan 11kw

[Puffy]

Has anybody out there got any clues on how to find and remove the pencil zinc on an Onan 11kw generator?. It’s time to replace it.
It seems like there may be an access port to the side of the generator from the starboard forward cabin in the book shelf, however the panel does not come out through the book shelf and it’s looks like I would have to cut it. There must be a better way and I hope one of you out there’s can help
We have the 4 cabin lay out.
Thanks.

[Bean Counter]

We have 3 cabin. A couple of years ago a very skinny mechanic was able to replace the zinc with top and rear sound box covers removed. The sound covers are easy enough to remove with right ratchet socket spanner. He knew what he was doing and did it by feel.

I am not that skinny so took off all the bathroom cabinetry/doors- about 30 screws and got access to the insulated plate a real PITA. The insulated plate comes off towards you and you have access to the generator heat ex-changer (with sound cover plate slid to one side). The pencil zinc is in the side of the heat ex-changer. This allows you to inspect heat ex-changer as well (our clogged up last year) - 6 years old. Took half a day

[Bean Counter]

Photo of access to heat exchanger (cap is off) and zinc bolt head is the one with yellow PTF tape around it.

[Bean Counter]

Oh and if you ever want to change the coolant the drain plug is on this side as well - the white tap fitting at the top right of the photo

[billknny]

Wow... that's truly amazing.

Did anybody tell Lagoon that the zinc on an Onan generator is an every 6 month maintenance item????

[Bean Counter]

Originally Posted by billknny

Wow... that's truly amazing.

Did anybody tell Lagoon that the zinc on an Onan generator is an every 6 month maintenance item????

Well I think Onan should put the heat ex-changer on the port side. Admittedly the Genny is shoehorned in to the front starboard locker, but I prefer it there than in the cockpit where it was for the 440. It is just one of those few things to deal with, at least there is clear access once you open the panel and you can see what you are doing.

A better alternative would be if the cabinetry was designed around the access panel, like in the back of a largish cupboard. In fact I think I could cut a 6 inch hole with a spin out in the access cover that would mean I could still get at the zinc without removing anything except the spin-out.

[CarlF]

I was once told at a boat show by an Onan guy who seemed like he'd been at Onan for a very long time that the zinc on the MD models never needs replacing. It was put there by the lawyers.

No idea if that's true. Just passing it along.

[billknny]

Originally Posted by CarlF

I was once told at a boat show by an Onan guy who seemed like he'd been at Onan for a very long time that the zinc on the MD models never needs replacing. It was put there by the lawyers.

No idea if that's true. Just passing it along.

"The lawyers?"

I know on my MD the zinc shows obvious signs of corrosion at the recommended replacement interval. I'll just keep changing it as recommended.

[Bean Counter]

Yep the Zincs do wear down. I guess it also depends on the sea water environment as well. You still need to check the heat ex-changer.
In the photo the zinc on the left was at 500 hrs, the right one had next 1000 hrs on it. We changed again at 2000 hrs and also needed to clean heat ex-changer.

[PaulinOz]

105 hours over two years, the previous year i was charged for the replacement of the zinc by the servicing company. But they did not change as this is the original fitment, painted white in the factory that was 2 years old and run for 105 hours. Lucky the next year the servicing company was a bit more diligent. Now after the latest cock-up with the cone clutches I am back to doing it myself. Not that I want to, I just need to know it is a: done and b: done correctly.

[feebs]

It is a good idea to use two spanners when changing this zinc - one for the zinc & other on fitting of heat exchanger. This way there is less likely hood of cracking the weld into the heat exchanger.

[sailcrazy]

and if you wait to long, the "head" will get corroded in, and when you try to twist it out the head can twist right off the pencil-or what's left of it. Don't ask me how I know!!!

[svinshallah]

Having the zinc pencil break off in the fitting is a common problem. The simple solution is to heat the fitting with a propane torch. The zinc will easily melt out like solder. Clean the threads with a tap or dental pick if necessary.

[sbaydreamer]

So you access from the starboard front cabin? The shelf?

[Bean Counter]

Originally Posted by sbaydreamer

So you access from the starboard front cabin? The shelf?

On the 3 cabin 450 (2011), access to the starboard side of the generator is through a panel that is behind the cupboard framing nearest the generator and next to the holding tank in the starboard forward master bathroom. The cupboard doors should be removed and then the 20 or so screws holding the internal shelving can be removed (a right angle driver drill fitting helps do this quickly) The screws are found in the frames and shelves some are horizontal some are vertical top and bottom. Once the shelves are removed the white fiberglass back panel can be unscrewed (take plastic screw caps off), and behind that is the insulated panel that lifts out. Behind that insulated panel is the Onan sound box that is undone at the top two locks with a coin and it slides to one side giving access to the generator. It gets faster with practice - done it 6 times now.