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K Engine 12V Rewire

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K Engine 12V Rewire

Post by JohnsBonita » Tue Aug 11, 2020 10:20 pm


This is my first time posting. I have a 1961 18’ Chris Craft Sea Skiff with a 95 HP K engine. I am currently re-wiring it and I have pretty much everything figured out except for a few items. I am hoping someone can help.

Ammeter Wiring - The original engine wiring diagram states to wire the horn (and other high amp loads) on the battery side of the ammeter as to not deflect the gauge when activating the horn HOWEVER I am planning on installing a “zero center” ammeter that displays charge and discharge amps so I was just planning on installing a fuse panel off the gen/voltage reg output (that feeds everything including fused feeds to the horn and bilge pumps) and just have the ammeter monitor charge/discharge current back to batteries? Any fault with this logic? Also, the scale of the gauge (Faria Chesapeake) is 60-0-60, it may be a little high but I feel it will still read? I currently don’t have an ammeter so I don’t know magnitude of charge/discharge current?

Gen And Battery Fusing - Do I need to fuse the gen/voltage reg output? What about the battery output to the ammeter (not the cranking path). If yes, what size/type fuses and where have people mounted the fuses? At the engine? I currently have a small wood board that the voltage reg is attached to, screwed into stringers near engine. I could try and mount the fuses there? What about a battery disconnect?

Engine Water Temp - What is the recommended scale for the engine water temp? The gauge I am looking at using is 120-220F. I am asking because my current temp gauge doesn’t work (or at least read anything because temp is too cool?)

Thanks for any help on above. I am also getting the engine rebuilt, so all indication will work. I am shooting for new wiring and gauges with a new engine (also I restored the boat a few years ago and am also rebuilding the trailer. I hope to have a new boat when done!)


John Hiddema
South Haven MI

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Re: K Engine 12V Rewire

Post by kiitos » Wed Aug 12, 2020 9:28 am


I can't help on your ammeter question but for fusing you only need to fuse accessories. Such as bilge pump, blower if you have one, navigation lights, spot light, etc. Don't fuse leads from the generator/regulator or horn.

You should have a water temp gauge that starts at 100 degrees unless you have a thermostat installed. My Ks (I have a twin engine 25) do not have thermostats. In the spring when the water is cold the engines run at around 100deg. As the water warms through the summer they run at around 110 deg.

'78 Chris Craft 30' Sportsman
'49 Chris Craft 25' Sportsman - Twin "K"s

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Re: K Engine 12V Rewire

Post by mbigpops » Wed Aug 12, 2020 9:55 am

I installed a fuse block on my runabout. It is mounted behind the dash on the side of the "glove compartment" out of sight. I would not mount anything electrical in the engine compartment that you can mount elsewhere for safety reasons.
In my opinion everything should be fused as if anything shorts you could lose a gauge or valuable item instead of the fuse. This includes the horn which draws a lot of current so I had to use an in line fuse and not the fuse block (not rated for that high of current).
Also, I would run everything but the horn through the ammeter. That way you can see the ammeter deflection when you turn something on or off. Your 60-0-60 meter will barely deflect when you turn on things like the bilge pump and navigation lights but you will certainly see when the generator kicks in and charges the battery.

1953 CC Rocket Runabout "Rocket Man"

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Re: K Engine 12V Rewire

Post by JohnsBonita » Wed Aug 12, 2020 5:10 pm

Thanks for the reply. I appreciate it.

To clarify the ammeter question. I am just planning on installing one blue sea systems fuse panel, in the forward storage area. The panel will feed all auxiliaries, including the horn. If I wired the horn on the other side of ammeter, per the original wiring diagram, I would need to install a separate, single fuse for the horn. I don’t see the value in doing that. If I use an ammeter that deflects in both directions, for charge/discharge, what does it matter?..that was my question.

As far as fusing the battery and gen feed from the engine to the gauge panel, I thought the ABYC says each “source” must be fused closest to the source. That is why I was asking about fusing at the engine. That is the only place you could install fuses close to the gen and battery “source”...but it sounds like that’s not required? The original chris craft wiring doesn’t show fusing but I think that was before ABYC standards?

As far as engine temp, that helps, thanks. Sounds like a 120-220 degf scale gauge is too high for average engine temps?

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