Hey Bob ... what year and which model of 42 do you have? ... which model of Twin Disc marine gears do you have?
I want to run mechanical transmission oil pressure and temperature gauges right at the gears in the engine room for several reasons:
- I am getting what I am near certain is a false positive Stbd. Drive Oil warning (alarm) light all the time ... I suspect the Stbd. gear oil pressure (alarm) switch (what this thread is really about) is stuck Open ... I'd like to see the actual oil pressure under various conditions to ease my concerns that I may actually have an issue with my Stbd. gear in my older new-to-me boat ... plus, my Twin Disc BOM (Bill of Materials build sheet) calls for 350-370 PSI @ 1,800 RPM and 180° F, minimum 335 PSI while cruising ... relatively high, as these things go ... I want to see for myself the operating pressures of both gears while cruising ... otherwise, all else is really guesswork ...
- oil temperature gauges will tell me my cruising oil temps ... again, a peace of mind thing, however, depending on temps seen, it will allow me to decide whether I need to go from Mobil Delvac 1230 (30W, 150° F to 185° F) to 1240 (40W, 175° F to 210° F) oil ...
If you're running MG-506 R and L gears (I suspect you are), I have a digital copy of the Service Manual SM-175, Document Number: 1015921, Revision E, August 1985 ... it is 31.34 MB, so, too big for here or attaching to e-mail.
What file sharing services do you use? ... I tend to use 4Shared.com, however, non-internet ad-saavy users seem to have trouble using the free interface.
Anyways, unless one of your gears is equipped with a Trolling Valve, you should not have an external filter cannister (mine does, on Stbd.[R], and uses the PUROLATOR P-192-04-3 cannister, and a Baldwin PT82-HD element) on the gear so equipped ... just an oil strainer that should be checked / cleaned whenever you change oil (easiest to pump / suction it out of the oil level gauge tube).
The audible (alarm? yes?) tweet you are hearing when shifting is not something I believe my boat does, however, my usage so far has been minimal (and I've been pre-occupied during maneuvering due novelty of my new-to-me 42' DCS' handling characteristics), plus, it's hard to hear anything over my Detroits from the flybridge, where any shifting I've done has occurred ... and, I have issues with my alarm electronic modules, so, do not think alarm is functioning correctly ... I have read here and elsewhere that an alarm bell / tone ('tweet' if you will) while shifting does occur amongst other owners and can be considered useful feedback ... and not indicative of any problem(s) per se.
Kevin Mc