Humminbird 798ci HD DI Combo depth readings at high speeds?

[gerty]

I have the above mentioned unit and am having troubles with my depth readings at high speeds. I would really like to see how others have their transducer mounted to compare it to mine. If anyone would be willing to share a picture/s of what their mounted transducer looks like I would greatly appreciate it. I have asked several people to look at mine and they all feel it looks like it is mounted correctly. I have lowered it once already adn that did not seem to help. The only thing I can think of is that it is getting prop wash and I may need to mount it on the other side of the motor so as the prop rotation will not affect it as much.

Any pictures and or suggestions would be great.

[Nick Kuhn]

Mine is pretty close to the motor on the starboard side. I have it mounted pretty low and angled slightly forward. Never has a problem reading at speed unless it was really choppy. Even then it still gave a depth, just not a very good picture.

[TruthWalleyes]

People are only willing to talk about lowrance on this site. So i'd suggest using a search engine, and type in BBC Humminbird. They've got the info your looking for with pictures of installations, etc.

[Northlander]

Truthwalleyes I dont think thats true at all. People talk about all types of units on this site.

As far as where you have your ducer mounted its so much of a boat motor set up guessing game its crazy. I looked at my neighbors and others boats boat and did what some of them did but it didnt work on my boat. I played around with mine and tried about 8 different spots. I tried closer to motor, farther away, higher, lower, more tilt, less tilt and finally got close to what I want. Its still not perfect but good enough for now. I got sick of playing ducer games and went fishing instead.

I have the bird 957c. Make sure you have a good board and move the ducer around until it starts getting better. I know its sucks but thats the only thing I found to work. You can do a search for unoficial humminbird HSOforum and thats a very helpful site for bird users too.

[gerty]

I have mine mounted on the port (left) side of my motor. According to some info I have found, with the way my prop turns, it should techinically be on the starboard (right) side of the motor. That is really the only info I have found that tells me anything. I was hoping to get it working where it is at so I do not have to mount another board on the starboard side and play around with moving it over there, but I guess I may have to. Thanks for the info so far.

[Nick Kuhn]

Is there anything about the hull in front of the transducer that would create cavitation?

[TruthWalleyes]

Cavitation is causing your problem. Be sure the transducer at full speed is skimming the water, not plowing through it as it will create its own cavitation if not set so the transducer parting line is at the same height as the bottom of the hull.

Look behind your boat when going full speed. Is the transducer even in the water? Partially?

Get on your hands and knees and look under your boat. Is there anything creating cavitation? Ribs, Rows of rivets, Seams, etc... You want to stay as far away as possible from any of these, which may only be 3-6" depending on your style of boat.

If your transducer is too far to the outside of your boat it will likely come out of the water on slight turns.

Hope this helps....there should be about 50 pages in the manual to help you figure out the correct location for your deucer.

[CaptainMusky]

People are only willing to talk about lowrance on this site. So i'd suggest using a search engine, and type in BBC Humminbird. They've got the info your looking for with pictures of installations, etc.

Why not post pictures of your installation since you were so eager to share pictures in the side imaging thread?

I am sure there is cavitation getting created by your hull. Look for ribs that run the length of the hull or at least near the transom and make sure you are not directly behind them. Also, if you have an aluminum boat be cognizant of rivets, etc, that may be all it takes to mess with a transducer at speed. If it is a deep vee boat it takes some putzing to get it right because of the water they displace. One key is to make sure the transducer is level side to side when the boat is floating, not on the trailer. I found an awesome site a while ago that had very good information about mounting transducers, but cant find it now. If I find it I will post a link. It was great, with nice illustrations, etc.

[TruthWalleyes]

Why not post pictures of your installation since you were so eager to share pictures in the side imaging thread?

Since we don't have the same boat, it would be absolutely pointless to post pictures cap'n....Don't be angry becasue you don't have that technology yet.

[CaptainMusky]

Since we don't have the same boat, it would be absolutely pointless to post pictures cap'n....Don't be angry becasue you don't have that technology yet.

Thats funny, I didnt notice him mention what boat he had.

Besides, even if the hull is different it may give some ideas.

Not angry, just help the guy out instead of taking a poke at lowrance when it was irrelavent here.

[TruthWalleyes]

See Avatar of OP, and i gave him the HSOforum of many many pictures of different boat hulls with transducers on them....

[CaptainMusky]

See Avatar of OP, and i gave him the HSOforum of many many pictures of different boat hulls with transducers on them....

Yeah, I can tell by the picture that he has a lund, smokercraft, sylvan, northwoods, alumacraft, starcraft boat. I could tell by the navigation light. LOL

[TruthWalleyes]

I can tell it's nicer than mine!

[gerty]

To stop the back and forth, I have a 1992 Alumacraft Dominator, with a 1993 40hp Yamaha 2 stroke. I doubt it is nicer than either of yours!! .

In any case, I looked for all the different structures, rivets, etc. before mounting it. I am between two rivet lines so that should not be an issue. When on plane, I can see the ducer skimming across the top of the water, maybe slightly into the water. I have lowered it a bit already, so if it was in too far to start, it is in farther now. As mentioned before, the manual does say that the direction the prop turns will affect which side to mount the ducer on and mine should be opposite of what it is. The prop may be causing the cavatation you talk about. I have used that BBC HSOforum before. Unfortunately, the only pictures they have of mounted transducers are on boats where their trolling motors are worth more than my entire boat

Not that it matters since they are different units, but the ducer is mounted in almost the identical spot my Lowrance was mounted . That unit never had any issues at higher speeds.

Continued thanks.

[fishwater]

My impression is that high speed 2d readings with the bird SI ducers (hd and compact) is a bit tricky and not as forgiving as a lowrance skimmer. I've heard it is possible, but most folks use a 2 transducer setup for a number of reasons.

It's worth playing around with, but often the angle for optimum high speed 2d and low speed SI are not congruent. I've heard positive reports of folks running the vex alumaducer with success for high speed readings.

I get good readings to 30mph with my humminbird, after that it hit or miss.

[gerty]

Fishwater - my unit is not an SI unit. Sonar, down imaging and GPS, but no SI. My boat tops out at about 26mph, so I think I should be able to get good readings. Just need to find the right location I guess.

[TruthWalleyes]

See If you boat is here: Mounting Pictures

[eagle_3464]

I have had the 798ciHDSI for a couple of months now. I have not had any issues with reading depths at high speeds (40 mph). I don't change my chart speed for high speed so the depth contours on the sonar rise and drop nearly vertical. Other than that I have a digital depth reading and bottom sonar reading at speed. My ducer is mounted to the right of the motor just shy of 15" (thats as far as I could get with existing board). Mounting instructions call for a minimum of 15" I believe. I followed the instructions as best my boat would allow and haven't had any issues. Did the same on my brothers and no issues there either. I'm sure your ducer is different without the SI. I would get it moved to the right and follow the mounting instructions for distance over, depth from bottom of boat and angle adjustment.

I have read that some have issues with the Lakemaster map not regenerating fast enough at speed. I haven't had those issues neither. Very happy with my 798.

[gerty]

Truth - thanks for the link. I had looked there earlier. No luck.

Eagle_3464 - thanks for your info. I guess I am going to have to bite the bullet and move it to the other side as recommended and see what happens. Guess I will just mount another plate on that side and leave the current one there in case I ever need to put a different one back on this side.

Thaks again.

[CaptainMusky]

I have read that some have issues with the Lakemaster map not regenerating fast enough at speed. I haven't had those issues neither. Very happy with my 798.

I believe these issues are corrected if the user chooses "North UP" for orientation on the map panel.

I personally dont like using that orientation, but I remember reading it on the Lakemaster site a while ago.

[eagle_3464]

Unit came with "North up" as default and I have not changed it. It's no diferent than looking at a road map and the direction indicator arrow points toward whatever structure or waypoints are in the direction you are going. I always go by the direction arrow to adjust my course to the desired destination.

[eagle_3464]

gerty, hope these pics help you out with positioning.

I leveled my ducer with the boat side to side as recommended per instructions. Leveling with the way the boat sits in the water is not correct. Your load distribution in the boat will make a difference on how the boat sits. But on plane, unless you are severely loaded to one side, your boat should be running pretty level. Adjust the ducer tail down slightly and that may help with speed readings. To high at the tail will be shooting the signal behind the boat. You will want the signal slightly forward so the ducer can still receive the return. Hope this makes sense.

[CaptainMusky]

eagle nice pics and you can clearly see how important leveling the transducer is because you have a deep vee hull. One point of clarification though, I made a comment about leveling the transducer as it sits in the water versus on the trailer because many boats do not sit level on the trailer and the ground may not be level that its parked on. Its a tricky thing to get right and I had to fiddle with mine a couple times to get it just right.

[CaptainMusky]

Unit came with "North up" as default and I have not changed it. It's no diferent than looking at a road map and the direction indicator arrow points toward whatever structure or waypoints are in the direction you are going. I always go by the direction arrow to adjust my course to the desired destination.

North up twists the map orientation so that north is always at the top of the screen. Course up (which is what I prefer) keeps you heading toward the top with direction arrows where North is.

I dont give a [PoorWordUsage] where North is, I want to know where Im heading and when following contours on a map chip its much easier (for me) to follow them with course up than north up.

[gerty]

Eagle - Thanks a lot. They will help a lot when I look at repositioning mine to the other side. I do not see a lot of difference in the way mine is mounted now, just that it is not on the suggested side of the motor. I really appreciate you taking the time.