Topic: 798ci SI

[mikedatlga]

I have a Tahoe fish and ski and am installing a 798. Had a question about the transducer location. If I mount above the bottom of the boat I don't expect to get good returns at higher speeds but will this position be ok for slower speeds?

[sonar2000]

Possibly but you might also get reflection from the motor. which could be reduced if you raise the motor while trolling (if you do that)

You might look thru the gallery of this forum at others who have posted their pictures of mount.
Or search the forum for mounting posts. (be creative in the search argument and try several arguments varying them.

You could try and sticky tape a temp mount to see how it works at slow speed.. Until you find the optimum position...

Chuck

[LocDown]

Maybe to the right of that trailer bunk, just right of the stepped hulled section.

[mikedatlga]

This is a pic from the side. I thought I might get obstruction from the motor if I went outside of the trailer bunk.

[Humminbird_Greg]

You may get some obstruction from the motor if you go outside the trailer bunk.

The possible issue I see with mounting the transducer right under the motor is not of obstruction but of causing an air cavitation bubble to form at higher boat speeds which will cause water flow problems through the propeller and possible water intake problems.  No way to tell if it will or will not except to hard mount it and try it…

[mikedatlga]

I would assume water intake problems could cause overheating. What would cavitation do?

[Humminbird_Greg]

The cavitation could possibly form an air bubble at the water intake area and not allow cooling water into the motor.  This air bubble could also be large enough that it will affect the propeller by not allowing water to flow through it.

[sonar2000]

Are you serious or only hypothesising..

Chuck

[Humminbird_Greg]

This information came from Customers who installed transducers in front of their motors.  When they removed or moved the transducer the problem went away.  I would say that is pretty conclusive.

[sonar2000]

I find this a bit hard to believe...Would like to see some more documented study or case history. 
What a shame for a transducer to affect the propeller..

Chuck

[mikedatlga]

I will post what I experience. Should be trying it out this weekend. The original question was also more about the height of the transducer. I understand if I go above the bottom of the hull I will most likely lose signal on plane. Would it still work at lower speeds? It should make it less likely to hit any obstructions. Would it put less force put on the transducer mount at high speeds with it moounted higher?

[mikedatlga]

and thanks for the feedback

[sonar2000]

Mike, certainly if you raise the height it will lessen the hitting obstructions, and yes it may lose signal on high speeds (as in above trolling). Depending on the height you might find side interference with a motor, which can be raised while trolling in some cases..

As you can see from other posts on location of transducer, many have opted to use the SI on troll and for planeing speed use a thru the hull 2d transducer.

All good question you ask and ones that need to be taken care of before you make a final placement  for use..

Chuck

[Humminbird_Greg]

I will post what I experience. Should be trying it out this weekend. The original question was also more about the height of the transducer. I understand if I go above the bottom of the hull I will most likely lose signal on plane. Would it still work at lower speeds? It should make it less likely to hit any obstructions. Would it put less force put on the transducer mount at high speeds with it moounted higher?

Yes
Yes
and Yes

[mikedatlga]

I silicon caulked a 1/2" piece of star board marine plastic to the transom and mounted the transducer to that. Just didn't want to start drilling in transom until I knew where it needed to be. Got good returns on SI, and did not have any problems with cavitation. Did not notice any issues with cooling either. Thanks again.