Bottom breaking up over 10kn - transducer placement advice

 Hi guys,

 

I'm sure this is a frequent question, so apologies in advance for covering a common topic. I've just installed and tested a Furuno 628 on my boat. I'm stoked with the unit and reading under about 10knts, however once I get above 10knt the image starts to break up and loose bottom.

 

I tried playing with the settings and increasing the scroll speed etc but nothing seemed to help. This makes me think that the transducer placement might be an issue - even tho I followed the instructions to the letter and was super careful.

 

I've attached some pictures of the placement. 

Please ignore the apparent swiss cheese appearance of the hull. The previous owner seemed to have a million holes drilled so I had to drill them all out larger, fill and resin over. Doesn't look pretty but I'm alot more confident that it is water tight now. 

 

My guess is that it might be too close to the engine ? I did that because the are strakes running down the hull and I wanted to avoid the previous holes that I repaired. I did have a look over the back when my boat is underway is there is nothing the even resembles clean water behind my boat

 

Interested to hear any opinions. 

 

Cheers !

 

 

 

Image Upload: 

Darren253's picture

Posts: 333

Date Joined: 23/07/16

There is lots of talk about

Wed, 2018-02-14 14:16

There is lots of talk about this on the Simrad/Lowrance page on Facebook and The Hull Truth.

  • Check that there are no chines/pickups/ports forward of the transducer that could be disrubting the waterflow before it hits the transducer.
  • Try adding the 4.5deg wedge to angle the rear of the transducer down.
  • That height should be good but maybe try raising it 3-4mm to the LHS edge of the transducer is exactly level with the hull.

 It's all trail and error, i.m cuirrently going through it myself.

kirky79's picture

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Date Joined: 13/01/12

 It looks pretty good, as

Wed, 2018-02-14 14:31

 It looks pretty good, as Darren has said maybe try the wedge to get the back edge down a little more 

bleicester's picture

Posts: 180

Date Joined: 10/09/14

Before moving the transducer

Wed, 2018-02-14 15:47

One way to tell if you need to raise or lower your transducer is to monitor the display as you make a steady turn left or right while maintaining a constant speed.

Assuming transducer is mounted on starboard side:

- If the image improves while turning to port you need to raise the transducer. 

- If the image improves while turning to starboard you need to lower the transducer.

 

 

Posts: 42

Date Joined: 03/11/12

 My moneys on it needing to

Wed, 2018-02-14 16:49

 My moneys on it needing to go lower going from the photo . A side on photo would be better to tell that plus angle

Faulkner Family's picture

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Date Joined: 11/03/08

 looking at the pic i would

Wed, 2018-02-14 17:31

 looking at the pic i would say go a bit lower. i think the right hand side should be level with the hull. placement looks ok tho

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Francis's picture

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Date Joined: 17/06/08

Aimar P66 - added side photos

Wed, 2018-02-14 18:47

 Interesting responses - really appreciate it. After doing more searching and research there are alot of forums that suggest running the Airmar P66 about 10mm lower than recommendations. 

 

I've taken and added some side on shots with a straight edge placed along the hull line. It does look like it's a little bit high. Will try to drop it 10mm. The wedge that comes with the P66 seems to create a large angle so I am reluctant to put that in yet. So maybe I will lower it and try again, then I'll add the wedge if still no luck.

 

I think I know the answer to this one, but keen to hear what others would do - obviously I squirted marina sika in the holes and on the screw threads when I installed this. Would it be better to completely remove each screw, remove as much of the dry sika as possible and re-apply sika ? Or if I only wind them back enough to lower the height, then tighten them back up will the sika still form a seal ?

Tim's picture

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Date Joined: 26/09/06

Lower

Wed, 2018-02-14 19:21

10mm lower should improve it. Try it first before adding any more wedge. 

Best bet is to just change one thing at a time so you are sure what improved or didnt

Posts: 42

Date Joined: 03/11/12

 Drop it 15mm mate going off

Wed, 2018-02-14 19:34

 Drop it 15mm mate going off your photo angle looks good . I have a p66 on the opposite side of a tm260 and it sounds really well up to 20 knots or more

sea-kem's picture

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Date Joined: 30/11/09

 Yep I agree with dropping

Wed, 2018-02-14 21:19

 Yep I agree with dropping but try 3-4mm or so at a time. I found my sweet spot that way. 

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Love the West!

Posts: 20

Date Joined: 13/09/16

Just installed one myself

Thu, 2018-02-15 08:30

Hey mate, like you I've recently installed one myself (FCV 628 and a P66) and I’m getting solid bottom in over 20 knots (very fair conditions)

My P66 is definitely installed a lot lower than yours, try moving it as low as possible without drilling new holes. You may be lucky and this will do the trick.

The only time I have lost bottom is when I smash through/over solid wind chop but I am putting that down to air moving under the hull. (or when i lift the prop )

 

Francis's picture

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Date Joined: 17/06/08

 Excellent - I will start

Thu, 2018-02-15 10:20

 Excellent - I will start dropping it and give it a good test tomorrow ! Will post an updated photo of the eventual location that improves the reading (if it does indeed improve the reading).

 

thanks 

Posts: 234

Date Joined: 28/07/11

 Put that bracket as low as

Thu, 2018-02-15 20:01

 Put that bracket as low as it will go and you will be laughing.

just dhu it's picture

Posts: 1065

Date Joined: 14/05/09

Drop unit

Fri, 2018-02-16 06:15

 as the other said drop another 10 mm.  If you have on going issues I would also make up plate from rear of  transom out to transducer  so to eliminate any gaps where water and air especially can form between to two surfaces.  

ranmar850's picture

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Date Joined: 12/08/12

One aspect not mentioned here.

Fri, 2018-02-16 09:40

 I have seen it discussed at length on other forums, and that is the actual placement relvant to prop rotation. For example the OP has it mounted on the downsweep side of the ( assuming RH rotation) prop. Conventional wisdom in other places states it should be on the upsweep ( ie, in this case ,left) side of the prop. Let me stress i have no opinion on this subject, just throwing it out there for comment.

Posts: 70

Date Joined: 05/08/16

When it come to the perfect

Fri, 2018-02-16 13:46

When it come to the perfect set up with p66 they need to be buried passed disturbed water. Usually on the side closed to the keel needs to be 10-15mm lower then the Hull. The next thing is angle, working off your Hull isn’t a true indicator. You need get on the plane with a level and work out how your boat sits then level your tranny from there. Most smaller boats quinnys, savages etc ride nose down on the plane. I had to give mine some angle and looking at it looks wrong but mine reads 29knots flat out even in crap conditions. One way to work out if the angle is wrong is if your loosing bottom while going into the plane as the nose drops if so more angle. Just play around with it mate once it’s set mark around it with a permanent marker and you will always have the spot to mount it

Posts: 70

Date Joined: 05/08/16

When it come to the perfect

Fri, 2018-02-16 13:46

When it come to the perfect set up with p66 they need to be buried passed disturbed water. Usually on the side closed to the keel needs to be 10-15mm lower then the Hull. The next thing is angle, working off your Hull isn’t a true indicator. You need get on the plane with a level and work out how your boat sits then level your tranny from there. Most smaller boats quinnys, savages etc ride nose down on the plane. I had to give mine some angle and looking at it looks wrong but mine reads 29knots flat out even in crap conditions. One way to work out if the angle is wrong is if your loosing bottom while going into the plane as the nose drops if so more angle. Just play around with it mate once it’s set mark around it with a permanent marker and you will always have the spot to mount it

Francis's picture

Posts: 200

Date Joined: 17/06/08

 Just in this, does the

Sat, 2018-02-17 17:34

 Just in this, does the additional angle cause problems when you are drifting or going slow searching for reef?

 

I just wonder if the angle might make the beam shoot a fair way in front of the boat when drifting in 30-40m of water ?

 

Ive added the wedge and will take it for a test tomorrow I hope, but like you said it does look a bit too much.

Francis's picture

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Date Joined: 17/06/08

 Cheers guys, I dropped it

Fri, 2018-02-16 16:36

 Cheers guys, I dropped it today and tested, then dropped more (as low as I could go with the screw locations) and tested again. I think I got marginal improvement but not much. Otherwise I was super happy with the reading I was getting (even if the fish I appeared to be seeing didn’t seem to want to bite!)

 

Will try to insert the wedge and see if that makes any difference, otherwise I might need to patch up the holes and try again.

 

Interesting point re: being installed on the downsweep side. I’ll have to revisit this and read into it as I thought I put it on the correct side.

 

Darren253's picture

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Date Joined: 23/07/16

I believe it is on the

Fri, 2018-02-16 17:08

I believe it is on the correct side too. I’m testing mine with the 4.5deg wedge tomorrow after various different height tests.

Francis's picture

Posts: 200

Date Joined: 17/06/08

 Good luck - will be

Sat, 2018-02-17 08:04

 Good luck - will be interested to hear how you go!

Francis's picture

Posts: 200

Date Joined: 17/06/08

 Just a follow up to close

Mon, 2018-03-05 18:48

 Just a follow up to close this out and help anyone else out - I ended up having no luck with the original mount location OR using the shim/wedge when over 10knt, so I moved the transducer over a bit closer to the keel and removed the shim. I added a new photo and you can see the 3 previous holes  (need to finish the patch job). I didn't have to move it over too far and I can still go lower if needed but I am getting a solid reading at 20knts now ! Very happy. 

 

It does start to break up over 20kn, but if I turn to starboard, the transducer goes deeper and the image clears up. I don't think I will be bother lowering it further tho because I can't be bothered playing around with silicone again and I rarely exceed 20knt unless im done for the day.

 

I also changed the Transducer setting from "600W" to "525STID-PWD". Apparently this is the part number for the P66. Not sure if that actually helped or not but I'm super happy with the result now.

 

Hope this helps someone else.

 

Cheers