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Multimeter / wiring / chartplotter / fishfinder

  • #1
    Registered Users Posts: 232 ✭✭ Mick Tator

    I recently bought an old motorboat. The wiring needs to be tidied-up as there are several strands of unidentified wire going nowhere obvious and others that are disconnected/loose and could be removed.

    First question - Any recommendations please for a reasonably priced clamp multimeter and for tinned connectors? (Is the stuff advertised from China junk?)

    Second question - I’m thinking of buying a 9” chartplotter preferably with combined fishfinder and using an in-hull transducer. I know I/H comes at a cost of some quality loss, but I don’t want to bore holes in the hull if possible. Nor do I need anything super sexy (but I like Garmin), just want to see where I am, what depth is under the keel and if there are fish in the salty water. All seem to recommend through-hull or transom-mount but the latter will not work on semi-displacement.

    The VHF is DSC capable but not registered here, so I might go the NMEA route and build a separate new ‘ring’ to integrate all as I’d like to add voltmeters and eventually upgrade the fuel tanks with senders. Should I do this or keep separate instruments as back-up?

    Any recommendations/comments please?


  • Halfords are good for multimeters and connectors also buy the rubber shrink wrap tubes to seal your connections I also like the shrink wrap connectors with solder inside.

    The Garmin echomap and striker are nice and not too bad on price, at the moment I have a piece of wood stuck on my transom holding 4 transducers :D without screwing into the hull might be another option than going through hull.

    I went digital with my engine but kept the old ones on the dash and piggybacked off them, it's nice to have a backup if the new Tec fails :)


  • Thanks Fergal,
    My post was because I’ve been to Halfords and MPD a while back with no success - neither carry a suitable clamp multimeter and Halfords couldn’t confirm that their connectors were tinned. MPD have the connectors, but in small blister packs and expensive. I’ll probably go to MicksGarage for the meter and buy the connectors/shrink sleeves elsewhere. I do like the glue type, new since I (years ago) installed a set of B&G wind dials and Loran. I hope my old crimping tool is suitable.

    I’ll email Garmin, I like their Echomap Plus but all the adverts for it mention through-hull or transom mount transducers, the latter won’t work with a semi-displacement hull (I also have trim tabs).

    I agree on keeping the oldstuff, my engine dials are analogue, I’m keeping them, but I need to upgrade some gear as the NASA log doesn’t work and an old Garmin 2” sceen GPS takes forever to lock on satellites.

    How do you manage your FOUR:eek::eek: transducers? Do they not interfere with each other, or have you got them operating on different frequencies? (I just need to see depth and if there are fish down there, not photograph a wreck or a mermaid’s bosom with sideview or chirp!)

  • I have no problem with the 4 transducers except for maybe a bit of prop wash on the surface, this is an image of a school of fish from the weekend it's on a Garmin UHD with a GT54 transducer this transducer is mounted on a poll that clips onto the bit of wood on the transom I can move the poll up and down and in any direction for when I use the live scope transducer also mounted on the poll.



  • Dont buy wiring for cars.....its not tinned

  • Thanks Fergal, that is an interesting ‘array’! I’ve guessed that my cruising speed is about 12 – 14 kts in ordinary sea conditions, but with trimtabs the wake turbulence would prevent it working. I have a smallscreen Garmin GPS Map but it’s not working properly or practical, hence wanting the upgrade.

    @nokiatom – Thanks, I agree, that’s why in my OP is asked about tinned stuff. MPD are ok for wire and I’ll probably buy it there as my crimper/stripper is in mm.
    Generally product advertising is not very clear, with ‘marine’ being lumped together with ‘automotive’. Some of the shrink tubing on the market is only 2:1 and others 3:1. I’ll probably buy the connecters in the US as the crimper can handle the small difference between mm and AWG and most US stuff appears to be 3:1

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  • I've had great results with Chinese multimeters but check the test leads carefully for high resistance.

    Most transom transducers have easily adapted to through hull for me. Most recent is a Lowrance Hook5 which their tech support advised probably wouldn't work through thick GRP. Set into a bubble free bed of Sikaflex it works perfectly. Manufacturers prefer to charge silly money for a proper through-hull but this has always worked for me. Only downside is water temp is more engine bay temp until the boat has been moving a while.

    On connections I've always religiously soldered and heatshrunk joints but I've found the solder can sometimes crack with vibration. The one solution that works really well in wet locations albeit ugly, is a simple terminal block screwed connector filled with petroleum jelly as advised by an old auto-electrician. I also wrap them with self amalgamating rubber tape and works well. Those solder filled great shrink connectors are neat but can be difficult to heat safely in confined spaces or dense wiring looms.

    Untinned wire works fine until it gets wet, then the water will wick it's way the length of the cable and turn it black after which it is almost impossible to make an electrical contact to it. Avoid.

  • How about somewhere like car builders solutions for connectors and crimps.

  • Daibheid wrote: »
    I've had great results with Chinese multimeters but check the test leads carefully for high resistance..etc

    Thanks Daibheid, that’s a very informative post.
    I rewired a boat I co-owned years ago and my late father (Brit. I. R.E. qualified) told me at that time to crimp and ignore solder for the reason you quote. Current boat has a covered wheelhouse and good side-decks with lockers under, so there won’t be direct exposure. Even with that I’m not going near anything other than marine grade wire & fittings. I’m planning on using tinned shrink connectors, the ones with the resin in them.

    Once I get the redundant wiring cleared I’ll look at what’s left on the bus – there might be room to run a loop for the NMEA stuff from that. There was a radar and an autopilot (no replacement planned) so the cable should be big enough.

    Water temperature is not an issue, I stay out of it! I’ve been focusing on Garmin as I had a Garmin Nuvi in cars for years and found it excellent and very intuitive but costly (additional maps). I know of the Sikaflex trick instead of ATF/castor oil reservoir but never thought of trying it in-hull with a transom mount transducer. I’ll look at the Lowrance models and see what they do, the transducer for the Hook5 is far cheaper than anything for Garmin, so it’s worth a punt if the ones for bigger screens are +/- the same€.

    I’ll have a look on ‘Wish’ for the multimeter, but on the few items I bought from China I’ve had mixed success, it’s hit and miss with their vendors.
    Thanks again.