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[tvorgitch]

I have a 1993 Catalina 34 with a M35 engine. My oil pressure switch does not work and may be leaking. I've tried a deep socket and a crows foot, but can't get access to the switch. Do I need to remove the exhaust manifold or is there some secret to removing the switch. Thanks.

[tvorgitch]

Ok, I see there is a Tech Article on this, but I seemed to have misplaced my membership info. Hopefully I can get that corrected.

[KWKloeber]

You might have the elusive switch that you cannot get a socket on.
It seems that there are some exhaust manifolds that are either slightly out of place or maybe the casing is different.  I don't see another reason why some can get at the switch and others cannot.

Read this thread
https://c34.org/bbs/index.php?topic=9533.15

I believe that Matt still has his magic socket.

Once you get it out you might consider installing a hose and remote switch (as Wb does on the B engines.)

[tvorgitch]

Yes, I've read that. Maybe the problem is that I have a "generic" switch and it requires a 1 1/16 socket.

[Ron Hill]

Guys : I wrote a Mainsheet tech note article on removing and replacing the oil pressure switch on an M25XP engine.

I pointed out that one of the main problems with the switch was the failure of the joint bond between the metal body and the Bakelite center.  I recommender that you clean the new switch and seal that joint with epoxy!!

A few thoughts

[Catalina007]

Yes Matt does still have the magic deep socket. (If you have a grinder you can one yourself)   He was nice enough to lend it to me this year.  Its the way to go so you dont have to remove the manifold.

[Ron Hill]

Guys : I know that I use a small 1/4" socket to remove the screw for the wire.  That way it was easiest to screw it with the attached wire in to the new sender.  Believe that I used a crows foot wrench to loose /remove the old one.  Don't remember if that sender was a straight or tapered thread?
Guess I just need to reread my Mainsheet Article !!

A few thoughts

[mregan]

I do have my "magic socket".  It's just a cut down socket.  Let me know if you need it and i'll ship it out.

[TortolaTim]

On the subject of oil pressure switches, has anyone "Tee'd" the switch and added an oil press gauge? I was thinking of replacing the ammeter gauge with one. Suggestions on parts/ sizes, etc?

[Ron Hill]

Tim : I hope that you, mean Voltmeter and NOT ammeter!!

A thought

[Noah]

I think what Ron was getting at is you should already have a volt meter on your engine panel, not an amp meter. If you don’t then your system has not yet been “properly” upgraded. Also, do you have the high temp alarm “upgrade” installed?
https://www.catalinadirect.com/shop-by-boat/catalina-38/electrical/high-temp-alarm-retrofit-m-18-m-25-m-25xp-m-35/

[KWKloeber]

TTim

“Yes.”
I’ve done this 3-4 times.

There’s two ways - the first is to remote-locate the switch and gauge sender as Wb did on the “A” engines and is currently on the “B” engines.  Wb has a part that’s a brass tee brazed onto a bracket that mounts onto the unused engine mount land - there’s an angle adapter for the oil port and an extension hose to the bracket. 

The remote mount can be anywhere - the original M25s had an extension hose to a block for the oil switch and a gauge sender (an option on Universal engine panels) mounted to the Hx bracket. See #s 11, 20, & 14 below.  I moved my switch over to the engine block when at about age 15 the extension hose deteriorated and started weeping.

See the hose, bracket, (2-prong) switch that’s on the A engines on the next pic.

The 2nd way is to extend the port with a 1/8” pipe nipple, but the tee should be supported (maybe by a bracket hanging down from a strap bolted to the exhaust manifold studs?)  The pipe nipple busting off at the engine block due to the weight/moment arm created could ruin a sailing day.

The port and switch are 1/8” JIS thread (Japanese Industrial Standard) which is functionally the same as 1/8” BSPT (British Standard Pipe Taper.)  McMaster carries an adapter and adapter nipples and BSPT fittings.
So you need to either get an NPT switch for the tee or stay with JIS thread and find a JIS/BSPT gauge sender. ###

### (all that said, the key difference is that NPT thread pitch is 27/inch and JIS is 28/inch.  So practically speaking you could screw NPT into JIS and *it works* but it’s not the *proper* way.
I did that mismatch before I learned enough to realize the engine and oil switch were not NPT pipe thread.)

[waughoo]

With these threads in the block being tapered.... can I safely assume that a banjo bolt at the existing oil pressure switch spot won't be an option?  That has been my preferred connection where possible.

[TortolaTim]

Ron, yes I meant voltmeter;-)
Noah, I do have the engine temp alarm installed
Ken, thanks for the info. I will definitely start running down those parts.