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Old 12-08-2018, 08:21 AM   #1
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Thru Hull vs In Hull Transducer for Raymarine i50

I'm considering installing a Raymarine i50 depth finder as a stand alone backup. Available transducers include the bronze B17 thru hull and a plastic in hull P79. Not sure which one will be the best and most reliable. Does anyone have good or bad experiences with either of these? Any downside to using a in hull type transducer? This will go on a Mainship 34' Pilot. Would rather not drill another hole in the hull if it can be avoided.

Am also considering the Raymarine i40 with a plastic thru hull P7 transducer. Is that a bad idea to have a plastic thru hull vs bronze? Does anyone have recommendations with the i40 vs the i50? Thanks for your time!!

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Old 12-08-2018, 08:50 AM   #2
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Old 12-08-2018, 09:20 AM   #3
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I can only input that I installed an in-hull transducer, the Airmar M260, to add fish-finding and bottom display capability to my legacy Raymarine C120. and I'm more than completely satisfied with the performance and capability the in-hull transducer provides. If you decide to go in-hull, be sure you have a good spot for it by reading the installation guide and any user posts describing their experiences.
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Old 12-08-2018, 09:30 AM   #4
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I had one of the plastic in hull P79's and it worked fine.
Mine was digital depth only.
I decided to replace it with a thru hull to upgrade to fish finder and temp capability.
I would think as a back up depth unit it should work fine - I would test location(s) prior to permanent installation - instructions included w/ unit.

Used P79's are available very reasonable on eBay if you decide to go that way.
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Old 12-08-2018, 09:53 AM   #5
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I have two sounders. One a sounder only although it has some other functions such as alarms , the other a small fish finder at my main helm.

Both transducers are inside the hull mounts. They work just fine. I'm not a fan of holes in the hull if not absolutely needed. Both are epoxied into place.

I do believe though that some depth sensing ability, range, is lost but accuracy within that reduced range remains. Yet they can both follow the bottom to approx 300 ft. The older sounder only type can follow to about 500 ft. although I have seen over 700 on a hard rocky bottom.

That's good enough for my purposes , anchoring and general help for nav. purposes, not really fishing.

Most sounders , fish finders can be had in internal mount type transducers so what is your purpose?

If just intended as a backup then use the inside mount unit and leave the holes alone.

For transducer mounting location testing a heavy bodied hair gel works well. I used Dippity Doo from the pharmacy. DOn't know if it is available where you are but something similar should be. It's easily cleaned up once the location is picked so then you can epoxy the T.D. into place. My own experience with the first sounder was keep it away from the engine as much as possible. My very old and long gone unit was driven nuts by the engine vibrations. Moved the newer T.D.s and they are fine.
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Old 12-08-2018, 12:13 PM   #6
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No experience with Raymarine specifically, but I recently installed a Humminbird digital-only sounder as a backup with an in-hull transducer. No problems with it and the depths indicated mirror my primary Furuno sounder. A few years ago I installed the same setup in my hardshell dinghy which also worked fine.
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Old 12-08-2018, 12:41 PM   #7
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In our Camano I installed a P79 in hull transducer with a Raymarine C80. It worked just fine, even as a fish finder. Make sure to use an adapter so it points straight down. I filled mine with mineral oil, although I've read that lots of things work, like antifreeze.
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Old 12-10-2018, 08:33 AM   #8
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Thanks all for your input!! Gives me confidence that the P79 will work just fine.
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Old 12-10-2018, 08:56 AM   #9
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If you have a cored hull, the coring tends to attenuate the signal from the transducer both coming and going.... in-hull works much better with non cored hulls
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Old 12-10-2018, 10:25 AM   #10
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I recently replaced my dead depth sounder with this Hawkeye model. Like you, I didn't want to have to haul out and put another hole in my hull. Hawkeye sold me a like-new refurbished model for under $70.

I have a solid hull and went with a shoot-through-the-hull installation. I set it up as shown in their video and bedded it with a slow setting epoxy. It works great.

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Old 12-10-2018, 11:03 AM   #11
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Originally Posted by sammy999 View Post
Would rather not drill another hole in the hull if it can be avoided.

Sam I think you already have your answer. I use the P97 for both my MFDs. No holes, just a little math to get it aligned properly.

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