Johnson Overheat Bulletin 1990 - 60 HP Modification

[Shawnsgarage]

I have read numerous information on relocating teh tell tale to top of powwer head to avoid an air lock in the upper cylinder water jacket and it makes sense, however the procedure on where to drill doesnt make sense on my powerhead.

Can I drill a though hole in the cylinder head ? and head gasket ? it lines up directly into water passage
(Its already pre tapped NPT but not a through hole) pic attached ..
and run tell tale...guage form there?

I just rebuilt the power head (# 2 was blown) and did water pump and thermostat ....it runs great so far, but I dont want another melt down.

Please advise if you know what this pre - tapped spot on the head was designed for ? Or if I can use it ...seems like a good spot to me?

Thanks

[Shawnsgarage]

Anyone ??

Can i drill through the head ...and thrugh the gasket ? It lines up perfect to teh water jacket ..
Anyone know what this was pre - tapped for ?

Shawn

[Joe Reeves]

[QUOTE=Shawnsgarage;3722537]I have read numerous information on relocating the tell tale to top of powerhead to avoid an air lock. Can I drill a though hole in the cylinder head ? and head gasket ? it lines up directly into water passage, pic attached and run tell tale guage form there? I dont want another melt down. Advise if you know what this tapped spot on the head was designed for?/QUOTE]

(above quote has been edited to eliminate unneeded info)

The predrilled hole in the cylinder head is normally there to install a heat sensor, designed to regulate the reading of a dash mounted heat gauge. You do not want the heat sensor mounted directly within the water flow. You're also showing a tapped vertical hole at the cylinder head area of the crankcase. That would be for either a accessory of some kind or a factory holding tool location.

However, if this pertains to a water outlet tell tale or a gauge, this will probably not avoid another meltdown as no one is constantly staring at these areas and they're easily overlooked.

Your overheat warning horn should have sounded off before the engine was hot enough to do any damage, hence the "warning" title. The horn should beep one time, every time you turn the key to the ON position to indicate that the horn is operational. Does it?

To test the horn, engine not running, have the key in the ON position, then ground out the TAN wire (heat sensor) that you see protruding from the cylinder head.... that completes the waring circuit and the horn should sound. If it does not, find out why as that's the only warning you'll receive before the engine seizes up.

I know you're looking for a fast immediate reply, and I know that I haven't really answered your question BUT this has booted you back up to the top of the listing. Keep in mind that we're volunteers here, many of us are up in age, some aren't well, many aren't on the site daily, and it may take a day or two for a knowledageable member to reply with the answer you need.

[Shawnsgarage]

Thanks Joe,
I drilled the head at the factory NPT threaded location to run the tell tale since there is no way I am taking the chance and drilling into the block. Its only to eliminate the possibilty of an air lock in the upper cylinders water jacket.
I check my overheat sensor already and alarm works.