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Post by Juan on Jan 17, 2021 5:47:18 GMT -6
Has anyone installed one of these or have any experience with them? Looks like it would be more accurate than a pressure operated speedometer and a lot easier to install. Just wondering if there are problems like picking up a satellite?  |
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catchersrock
Ensign
Posts: 548 
Location: Maiden NC
Sea Pro model and year: 2020 Sea Pro 228
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Post by catchersrock on Jan 17, 2021 13:36:43 GMT -6
You have a fish finder/GPS unit, right? Just overlay SOG (Speed over Ground), shitcan that pressure speedo, and put something else in that hole. They make radios that fit in that hole.
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Post by Juan on Jan 17, 2021 14:28:48 GMT -6
You have a fish finder/GPS unit, right? Just overlay SOG (Speed over Ground), shitcan that pressure speedo, and put something else in that hole. They make radios that fit in that hole. Yep, I already have a speedometer in the fish finder/Chartplotter but I want something just for looks and to fill an empty 3" hole in the instrument panel and I'd like it to work. I thought about a radio but my VHF radio has FM radio and I also have a bluetooth speaker and no where to mount other speakers so don't need a radio.  |
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Post by freezerfiller on Jan 17, 2021 17:34:49 GMT -6
Accuracy is definitely better (although slightly delayed) as your regular speedo does not take current into account.
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Post by Juan on Jan 18, 2021 5:00:05 GMT -6
Accuracy is definitely better (although slightly delayed) as your regular speedo does not take current into account. GPS has a reputation of being the most accurate but now that you brought it up... explain the current effect on a regular water pressure speedometer to me. The speedometer always reads higher and I think I'm going faster when running with the current and slower when running against the current. Seems to me it should be the other way around since when running against the current wouldn't there be more water pressure going through the hose and isn't it water pressure that moves the speedometer needle?  I'm going to order one of these gps meters from China just to fill the hole in the dash. We'll see how it works if it ever gets here. |
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catchersrock
Ensign
Posts: 548
Location: Maiden NC
Sea Pro model and year: 2020 Sea Pro 228
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Post by catchersrock on Jan 18, 2021 8:28:58 GMT -6
The "Pressure" speedo that is connected to your motor reads pressure against the leading edge of the lower unit. One of those holes. It is speed thru the water, not speed over the ground. If your running against current your speed thru the water will be higher than speed over ground. If you were in a river flowing 35 mph, you could run 35 speed in the water and zero speed over ground.
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Post by Juan on Jan 18, 2021 11:14:54 GMT -6
I'm real familiar with how the the pressure speedometers work via the pitot inlet on a lower unit. What I can't seem to understand is why a pressure speedometer would read faster speeds when running with the current and a slower speed when running against the current. It sounds logical that the boat would go slower against the current because of the added drag on the boat caused by the current BUT it also seems that running against the current would put more pressure through the pitot tube to the speedometer and cause it to read a faster speed rather than a slower one. |
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Post by freezerfiller on Jan 19, 2021 17:15:27 GMT -6
Mine reads just the opposite. If I am going against the current my speedo reads (hypothetically) 38 and my gps reads 36, with the current my speedo reads 38 and my gps reads 40.
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Post by Juan on Jan 19, 2021 17:49:49 GMT -6
Mine reads just the opposite. If I am going against the current my speedo reads (hypothetically) 38 and my gps reads 36, with the current my speedo reads 38 and my gps reads 40. Maybe I stated it wrong but that's what I would expect from a pressure speedometer.  Higher speed registered when running against the current and lower with the current when in reality (and by gps) you're going slower against the current and faster with it. I need to check the pressure speedometer against the gps next time I'm fishing in a current. |
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Post by Juan on Jan 23, 2021 14:42:41 GMT -6
Got it installed along with a volt meter for the trolling motor battery. Turned out nice imo Before:  After:   |
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catchersrock
Ensign
Posts: 548
Location: Maiden NC
Sea Pro model and year: 2020 Sea Pro 228
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Post by catchersrock on Jan 25, 2021 7:52:14 GMT -6
very nice
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gtinga
Petty Officer
Posts: 234
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Post by gtinga on Jan 25, 2021 19:09:41 GMT -6
As it was explained to me: If your pressure speedo reads 35 that's how fast you are going thru the water regardless of the tide. If you are running against the tide you are still going 35 thru the water but your speed over ground is reduced by the speed of the tide. If you are going with the tide you are still going 35 thru the water, you speed over ground is that 35 plus the speed of the tide. Kinda like flying cross-country with or against the jetstream. Juan, nice bit of hardware, where'd you get it?
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Post by Juan on Jan 26, 2021 6:07:52 GMT -6
As it was explained to me: If your pressure speedo reads 35 that's how fast you are going thru the water regardless of the tide. If you are running against the tide you are still going 35 thru the water but your speed over ground is reduced by the speed of the tide. If you are going with the tide you are still going 35 thru the water, you speed over ground is that 35 plus the speed of the tide. Kinda like flying cross-country with or against the jetstream. Juan, nice bit of hardware, where'd you get it? That gave me a headache.  I have noticed that there's about a 1 or 2 mph difference between the gps and the pressure speedometer. I'm just going to ignore the difference since I'm pretty sure the gps is the most accurate reading and I can't understand the pressure meter's differences with and against a flow.  Got everything from Amazon. |
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Higher speed registered when running against the current and lower with the current when in reality (and by gps) you're going slower against the current and faster with it. I need to check the pressure speedometer against the gps next time I'm fishing in a current. 
I have noticed that there's about a 1 or 2 mph difference between the gps and the pressure speedometer. I'm just going to ignore the difference since I'm pretty sure the gps is the most accurate reading and I can't understand the pressure meter's differences with and against a flow. 
Got everything from Amazon.