Graham Nash Posted February 18, 2011 Report Share Posted February 18, 2011 I recent purchased a Garmin 750s radar/GPS/Sonar setup and ordered a "Thru the Hull" transducer believing in my ignorance that this would sit inside the boat and look "through the hull". I have heard that having an internal transducer is about 10% less efficient than having an external one but I was happy to accept the reduction in performance over the hag of fitting another external one. When it arrived I read the instructions (which is most unlike me) and it would seem that i need to drill a 3" hole in the bottom of the boat and fix this thing "Through the Hull" . I must be honest, this does not sound like the sort of thing i feel comfortable doing on a hull that is potentially keeping me on the dry side of a couple of hundred feet of water! Reading through the old posts & threads it would seem a fair few of you are using internal transducers (some even sound like they may be skimmer transducers actually inside rather than hanging off the transome). Do any of you know if my "thru the hull" transducer can be fitted inside the hull in a way that it will work, or do i need a specific type of transducer for fitting internally? Thanks in advance. Quote Link to comment Share on other sites More sharing options...
Mike Fox Posted February 18, 2011 Report Share Posted February 18, 2011 I've fitted my last two internal transducers on a block of plasticine inside the hull for fishfinders on my last two boats. Everything was moulded in well, and fittings made as solid as possible. Oh, and both "temporary" installations were never touched again. Reception is good, currently with a twin-frequency Garmin sonar unit connected to my combined plotter/fishfinder. It struggled a bit with clarity at 400' over the Hurd Deep however but is fine under 200', and does spot fish at these depths (funny they all swim off to the left mind...). However, I have seen other fishfinders on other club boats giving better images and clarity. Like you, am not keen on drilling a hole. It might be worth trying the plasticine trick, and seeing if it gives enough clarity/resolution for your needs? Mike Quote Link to comment Share on other sites More sharing options...
ChrisE Posted February 18, 2011 Report Share Posted February 18, 2011 Well, for a different point of view I have a couple of through-hull transducers on the yacht, as do most if not all yachts. Not many sink My through hulls have been across the Atlantic and into the Arctic Circle with no problems. Provided that you follow the manufacturers instructions there is not need to worry they are designed to be safe. Quote Link to comment Share on other sites More sharing options...
gjb Posted February 18, 2011 Report Share Posted February 18, 2011 I have got one in silcone , one in a in hull cup thing which is glassfibre fixed and filled with veg oil and a screw lid and the last one for my wreckfinder was drilled and fitted by Richard at holes bay marine this also turns inside a skin fitting to face forward or side veiw and all work well graham Quote Link to comment Share on other sites More sharing options...
Graham Nash Posted February 18, 2011 Author Report Share Posted February 18, 2011 I was all geared up to do that Chris, but as my boat is retreived onto a trailer at the boatyard I can see nowhere on any single skinned part of the hull that would not get run over by the rollers on the trailer. I doubt that would do the unit (nor the seal) much good. I have today spoken with MES who are going to take my transducer back and get me a nice new "in hull" one. I think i will feel happier with that. :-). I also find that the skimmer one i have on my transom gives me no reading at all at anything over displacement speed so am hoping that an in hull one will keep contact with the water at higher speeds than my existing setup. Quote Link to comment Share on other sites More sharing options...
duncan Posted February 18, 2011 Report Share Posted February 18, 2011 I was all geared up to do that Chris, but as my boat is retreived onto a trailer at the boatyard I can see nowhere on any single skinned part of the hull that would not get run over by the rollers on the trailer. I doubt that would do the unit (nor the seal) much good. I have today spoken with MES who are going to take my transducer back and get me a nice new "in hull" one. I think i will feel happier with that. :-). I also find that the skimmer one i have on my transom gives me no reading at all at anything over displacement speed so am hoping that an in hull one will keep contact with the water at higher speeds than my existing setup. I would suggest that if a correctly set up transom mounted transducer isn't working well at 'higher speeds' you aren't likely to get better performance from one shooting through the hull. I have 3 shooting though the hull at various places, stuck with various materials - and one on the transom. The latter wins all the time. Reasons for shoot thru are - no suitable transom, lots of in water hazards (twigs weed etc) in crusing area, no easy access to transom, not a lot of space on transom (twin engines/trim tabs etc) I agree that having a thru hull installed on a trailer boat anywhere near beds or rollers isn't sensible. Quote Link to comment Share on other sites More sharing options...
ChrisE Posted February 18, 2011 Report Share Posted February 18, 2011 I was all geared up to do that Chris, but as my boat is retreived onto a trailer at the boatyard I can see nowhere on any single skinned part of the hull that would not get run over by the rollers on the trailer. I doubt that would do the unit (nor the seal) much good. I have today spoken with MES who are going to take my transducer back and get me a nice new "in hull" one. I think i will feel happier with that. :-). I also find that the skimmer one i have on my transom gives me no reading at all at anything over displacement speed so am hoping that an in hull one will keep contact with the water at higher speeds than my existing setup. Yes, I can see that putting through holes on a trailered boat is asking for grief. Best of luck. Quote Link to comment Share on other sites More sharing options...
Graham Nash Posted February 18, 2011 Author Report Share Posted February 18, 2011 I would suggest that if a correctly set up transom mounted transducer isn't working well at 'higher speeds' you aren't likely to get better performance from one shooting through the hull. I had my transom mounted one fitted professionally Duncan but to be honest I have found it to be totally useless once moving. I am guessing it is faulty or it wasnt fitted properly but I dont know how to sort it so have bought a whole new setup. Quote Link to comment Share on other sites More sharing options...
Maverick Martin Posted February 18, 2011 Report Share Posted February 18, 2011 Graham I have a through hull set up and it works almost perfectly even up to 20+ knots. Picture sometimes lost at speed but very rarely. Your welcome to jump on and have a look anytime. Just lift my engine hatch and you will see the sounder in front of the engine bay left hand side. If you need any help just shout Martin Quote Link to comment Share on other sites More sharing options...
great white Posted February 18, 2011 Report Share Posted February 18, 2011 If you are struggling with a transome mount it is probably not lined up properly and suffering from cavitation. Mine is a simple skimmer transducer fitted inside the hull on epoxy, as Martin's mine works fine even at over 20 knots. I tried it in a few places bedded on blue tac, whilst deciding where was the best place [mines just about half way along the hull just off the centre line] Charlie Quote Link to comment Share on other sites More sharing options...
petesnr Posted February 18, 2011 Report Share Posted February 18, 2011 Could be just a slight change of angle on the transom mounted transducer will transform performance. Remember when you get onto the plane your bow is higher so the transducer starts to point forward rather than downwards. It's more likely to be turbulence causing air bubbles around the transducer--it might not be set deep enough. Never had a problem even with basic fishfinders that couldn't be solved by simple adjustment. Good luck. Petesnr Quote Link to comment Share on other sites More sharing options...
Graham Nash Posted February 19, 2011 Author Report Share Posted February 19, 2011 I will look at that during the week Peter. If I can get my existing setup as well as it should I would be happy to keep it as a back up or sell it. I would be reluctant to sell it as it is, cos it's pants! Quote Link to comment Share on other sites More sharing options...
wotu2uk Posted February 19, 2011 Report Share Posted February 19, 2011 My two skimmers both drop out at about 16 knots probably due to cavitation, and can take around 60 secs to reaquire when slowing, but they are both below water at all speeds (huge rooster tail from the sidescan one). John Quote Link to comment Share on other sites More sharing options...
Graham Nash Posted February 19, 2011 Author Report Share Posted February 19, 2011 My two skimmers both drop out at about 16 knots probably due to cavitation, Mine literally drops out at about 5 knots. Quote Link to comment Share on other sites More sharing options...
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