Boat Gauges messing up? Help….

Lund Fisherman with a Yamaha on it. Speedometer has not worked for years… but not concerned.

This past weekend I was having to back off throttle to keep it away from the 5800-6000 RPM’s (gauge reading), even when trimmed up less than usual. Small adjustment, so shrugged it off. Then after trimming down I was still reading high RPM’s. (normally I have to trim up quite a bit to get close to max RPMS…. and good with that.

Shortly after I realized trim gauge was not dropping all the way down as usual when trimmed down. Then later the RPM gauge was going to just over 6000, even trimmed down fully, and 3/4 throttle. Next it would just spin to fullest reading rpm, buried, even at half throttle, and running just perfectly.

RPM gauge seems ok at low rpm’s, trim gauge is just screwed up all the time now. Motor is not running at higher than usual RPM’s… it is a gauge thing.

Are these things connected in some manner? Is there some simple pickup, or whatever, or where do I start? I’m somewhat mechanically inclined, but this is all new to me… and I would like to avoid the long trip to deal with dealer having my boat for days if possible. Anyone have this happen before, or have a good suggestion on how the gauges work or read?

Not overly mechanically inclined myself but a couple of thoughts…

In relation to your speedometer- Check the little hole in the bottom of your drive shaft on the motor. Sometimes that gets clogged and that is normally what allows your speedometer to work as water shoots in that hole when your running and then operates water pressure to your speedometer.

As far as the high rpms– could it be that you may have the wrong pitch/prop on?

That’s about all i can offer with my 2 cents put in.

Good luck

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Lund Fisherman with a Yamaha on it. Speedometer has not worked for years… but not concerned.

This past weekend I was having to back off throttle to keep it away from the 5800-6000 RPM’s (gauge reading), even when trimmed up less than usual. Small adjustment, so shrugged it off. Then after trimming down I was still reading high RPM’s. (normally I have to trim up quite a bit to get close to max RPMS…. and good with that.

Shortly after I realized trim gauge was not dropping all the way down as usual when trimmed down. Then later the RPM gauge was going to just over 6000, even trimmed down fully, and 3/4 throttle. Next it would just spin to fullest reading rpm, buried, even at half throttle, and running just perfectly.

RPM gauge seems ok at low rpm’s, trim gauge is just screwed up all the time now. Motor is not running at higher than usual RPM’s… it is a gauge thing.

Are these things connected in some manner? Is there some simple pickup, or whatever, or where do I start? I’m somewhat mechanically inclined, but this is all new to me… and I would like to avoid the long trip to deal with dealer having my boat for days if possible. Anyone have this happen before, or have a good suggestion on how the gauges work or read?

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Throwing a new set of guages in yourself would probably be cheaper than paying a dealership to trouble shoot your issues. Not the cheapest fix but easy to do.

If I were to take a shot in the dark, I’d guess voltage regulator. It can mess with your gauges, specifically your tach.

What does your voltmeter read at 2000 rpm or above?

if you have a push/pull connecter in the wiring harness for the ignition etc. separate the two halves and see if you have a corrosion problem going on there also. May be the issue like mine once. Good Luck!

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If I were to take a shot in the dark, I’d guess voltage regulator. It can mess with your gauges, specifically your tach.

What does your voltmeter read at 2000 rpm or above?

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If I remember there is a voltage meter on the Lowrance… but not sure that is the same thing that would show this? That may just measure amp at the battery or something. There isn’t a gauge for voltage on the boat.

The fact they both acted up at the same time has me thinking there is something else wrong, and effecting them. BUT Is the trim gauge interacting with the RPM’s in any other way? I didn’t assume these were mechanical like the speedo, but the trim gauge could be? Electrical is the one thing I am least comfortable with. I’ll look for any connections that may be bad, if I can find a push pull thing? Making my lack of knowledge on this obvious ha….

Prop and such is same as all last season…. this is a gauge thing, or something effecting them.

Your speedo is most likely debris in the little hole on the leading edge of your lower unit. I clean mine with an old dental pick. Your tach might be a low battery or like someone else mentioned, a bad connection. Good luck.

First thing I would check is to make sure that you have a good ground circuit. Most gages are tied together with a common ground.

Ground loose or motor stator needs replaced perhaps?

Mine did sort of the same thing last summer, but it is a merc. Idling at 1200 the tach would jump to 3000 then down to 800 then to 2000 then back to 800 then sit on 1200 for a while. When I took off it would jump to 6000 at 1/2 throttle and then jump all over the place while running. The engine never sounded any different so I wrote it off as something wrong with the tach and not the engine. After we were done fishing I crawled under the console and wiggled all the wires and followed the connections wiggling them all. It hasnt done it since.