New prop causing fish finder to not read depth

[newdeal]

I have a 17 foot bow rider with a 90hp yamaha outboard. It had a 13.25x17 aluminum prop on it and was over revving. I just replaced it with a 13.25x19 Michigan wheel apollo stainless prop. I love the new prop. I had to grind the trim tab about to fit it but it does 42-43mph at 5800rpm now and was doing 36-37mph at 6300rpm before with two adults and two kids on board. The only problem is my fish finder used to work for depth at all speeds and now unless I am you f super slow it wont read depth and also it now causes a bit of a rooster tail from the sensor that it didn't before. I am not sure why this is happening or how to fix it but it happened as soon as I changed the prop and put it back in the water

 

[alldodge]

unless I am you f super slow it wont read depth and also it now causes a bit of a rooster tail from the sensor

My thought is something moved, maybe the sender. If it only happened when you were going faster then I would think it is due to stern lift. Your saying super slow (not sure what that means) so if the is idle and a slight bit above then check the angle of the sender. It may also just be to close to the prop

 

[SkiDad]

I vote stern lift. My ss prop lifts the stern more too

 

[Texasmark]

I did some iboats and www searching on the prop and it does look like it is a stern lifting vs bow lifting prop. Shape of it lends itself to that too as I don't see much if any rake. However, lifting the stern and effect on the transducer is confusing. If you lifted the stern enough to pull it out of the water the stern of the boat would be out of the water and I doubt that. what may have changed is the angle with the stern lift and as such you may be getting too many bubbles across it which could/would nullify your return. Drop it down a little at a time, or tilt it forward a little at a time till you get what you want.

 

[newdeal]

I tried trimming to get it to read but it didn't help. It does have a lot of rake which is why I had to grind part of the trim tab so the prop didn't hit it but it could be kidding the stern. I will try to pay with it a bit. Do indeed to pull it out of the water to do it?

 

[steelespike]

I'm thinking that somehow the sensor got moved in the process of messing with the prop.I would think that a stern lifter would tend to raise the sensor out of the water it acts like it is farther in the water.

 

[alldodge]

How slow do you have to go to get a reading?

 

[Texasmark]

It does have a lot of rake

Rake is bow lift, not stern lift! That's why bass boats use high rake props, to get the bow up, wetted hull area minimized.

 

[GA_Boater]

I'm thinking that somehow the sensor got moved in the process of messing with the prop.I would think that a stern lifter would tend to raise the sensor out of the water it acts like it is farther in the water.

Thinking the same thing. A rooster tail is usually a too deep transducer

 

[newdeal]

yup I pulled it out of the water today. It was a disaster of a day, went to a new river that looked like it should have been deep and had many boaters on it pulling tubes. We were going to go tubing also but I guess there are some shallow spots because I looked behind me and my motor was throwing up really brown water in the wake and so I tried to find deeper water, eventually did, but by that time there was no water coming out of the motor hole, the motor alarm went off for heat, I turned it off and we tried to paddle back but eventually some people towed us in. Turns out the water intake was clogged with mud and sea weed. Got it flushed out and its working again. However on the bright side I noticed the fish finder transducer was moved and so I flipped it down again and now its working normally again

 

[Texasmark]

yup I pulled it out of the water today. It was a disaster of a day, went to a new river that looked like it should have been deep and had many boaters on it pulling tubes. We were going to go tubing also but I guess there are some shallow spots because I looked behind me and my motor was throwing up really brown water in the wake and so I tried to find deeper water, eventually did, but by that time there was no water coming out of the motor hole, the motor alarm went off for heat, I turned it off and we tried to paddle back but eventually some people towed us in. Turns out the water intake was clogged with mud and sea weed. Got it flushed out and its working again. However on the bright side I noticed the fish finder transducer was moved and so I flipped it down again and now its working normally again

Was it flipped up without your knowing it when you started this thread and just now realized it?

 

[newdeal]

yeah, must ave flipped up when I was pulling it out of the water or putting it in to put on the new prop. I am loving the new prop though. Gets up to 45mph with just me on board, would only get to 37 with the old one

 

[JoshOnt]

yup I pulled it out of the water today. It was a disaster of a day, went to a new river that looked like it should have been deep and had many boaters on it pulling tubes. We were going to go tubing also but I guess there are some shallow spots because I looked behind me and my motor was throwing up really brown water in the wake and so I tried to find deeper water, eventually did, but by that time there was no water coming out of the motor hole, the motor alarm went off for heat, I turned it off and we tried to paddle back but eventually some people towed us in. Turns out the water intake was clogged with mud and sea weed. Got it flushed out and its working again. However on the bright side I noticed the fish finder transducer was moved and so I flipped it down again and now its working normally again

Likely became flipped up before and that was your issue. Good to hear you got it solved though.

 

[Texasmark]

Well it's nice we figured that out for the onlookers reading this thread. Easy to get folks confused and off on a wild goose chase.....aka effects of certain types of props, like in this case a high rake giving you stern lift when in fact it does just the opposite.

Glad you are up and running. I think 45 is a good, respectable speed for the guy that likes to play......like me.

 

[walleyehed]

Transducer moved because you increased speed from previous prop.. may have been enough increase to flip it up.
Glad you found the issue, but you can also create disturbance from the wetted area changing on a boat hull. Many things come into play when rake changes.