Tachometer not reading correct...?

[JonBoat55]

Thinking my tachometer is not reading correctly. I have a 99 Regal 1800 LSR, same year Merc 3.0. With four adult on board, I’ve gotten it to 35mph. (Speedometer is dialed in correctly).
Meter shows idle at 700, which is what is should be. But with WOT, it only shows 2000, won’t go above.
My question is, am I right to think the tach is incorrect? I’m guessing it’s impossible to get a boat going under load without going above 2000rpm.
Thanks

 

[HT32BSX115]

Thinking my tachometer is not reading correctly. I have a 99 Regal 1800 LSR, same year Merc 3.0. With four adult on board, I’ve gotten it to 35mph. (Speedometer is dialed in correctly).
Meter shows idle at 700, which is what is should be. But with WOT, it only shows 2000, won’t go above.
My question is, am I right to think the tach is incorrect? I’m guessing it’s impossible to get a boat going under load without going above 2000rpm.
Thanks

Howdy, Welcome aboard!

Tachometers are frequently off especially at higher RPM!

You may have other problems, but try getting a different tach and verify it.

Check this thread for other causes of low WOT RPM.
https://forums.iboats.com/forum/eng...ion-for-diyers-an-work-safe-search-version-of

Lots of good info in there check out #15 first.

Cheers,

Rick

 

[Rick Stephens]

Get a shop tach to check your actual.

With only you in the boat, how fast and what RPM at wide open throttle?

 

[JonBoat55]

Rick, a little under 40, RPS never goes above 2000, even during the hole shot

 

[HT32BSX115]

Rick, a little under 40, RPS never goes above 2000, even during the hole shot

If you're going around 40 mph (I assume measured with GPS) then your tach is absolutely way off.

Did it ever read higher? Or is this boat "new" to you?

 

[nola mike]

Another thing might be to check to see if the tach has a switch to set it for 4/6/8 cyl. (I can never remember which way the rpms are off with the wrong setting, and my brain isn't working atm, but I think if it was set at 8cyl it would read 1/2 of actual rpm). 40 mph on that boat seems about right.

 

[Rick Stephens]

Another thing might be to check to see if the tach has a switch to set it for 4/6/8 cyl. (I can never remember which way the rpms are off with the wrong setting, and my brain isn't working atm, but I think if it was set at 8cyl it would read 1/2 of actual rpm). 40 mph on that boat seems about right.

Yup. 18 foot boat, 130 HP Merc. Fortyish is probably pretty good. My 17 footer never would touch 4o when it had a 3.0L in it. My bet is you're pretty close, just need to fix up your tach. Follow Mike's thoughts or replace it. iBoats carries a few.

 

[JonBoat55]

Yeah, boat it "new to me". When reving it out of gear, it goes a little higher but nothing above 3k, and the motor is screaming when its up there.

 

[Scott Danforth]

keep in mind the factory tach was the cheapest tach the boat company could find that would make it past the warranty period.

Not sure if Regal used Teleflex or Faria back then. the old Teleflex (now manufactured by VeeThree) is sold thru Sierra as SeaStar here on iBoats as well as the Faria gauges

here is the manufacturers sites to find what you need, then use search at top of the forum to buy it.

https://www.v3electronicsusa.com/marine/analog-gauges/
https://fariabeede.com/2-pages/products_marine.php

 

[HT32BSX115]

Yeah, boat it "new to me". When reving it out of gear, it goes a little higher but nothing above 3k, and the motor is screaming when its up there.

yeah, looks like someone either set that tach wrong or it's defective "outta the box" !!

Oh......and NEVER REV A STERN DRIVE to high RPM out of gear! It serves no purpose and you can damage it.

Just get another tach if you cannot reset the current one.

 

[Rick Stephens]

Oh......and NEVER REV A STERN DRIVE to high RPM out of gear! It serves no purpose and you can damage it.

Absolutely concur.

 

[QBhoy]

Defo your tach. No way your boat will even plane at 2000 rpm. Never mind do 35-40 at 2000 rpm. Have you tried the usual flick of the gauge, haha.

 

[Rick Stephens]

Defo your tach. No way your boat will even plane at 2000 rpm. Never mind do 35-40 at 2000 rpm. Have you tried the usual flick of the gauge, haha.

My boat planes out at 1700. Makes it really tough to pull newby wakeboarders that want to go 17 MPH. Not that I disagree it's the tach, just not true that no way does a boat never plane at 2k.

 

[QBhoy]

My boat planes out at 1700. Makes it really tough to pull newby wakeboarders that want to go 17 MPH. Not that I disagree it's the tach, just not true that no way does a boat never plane at 2k.

Hi Rick

haha. Not quite what I said. I said there’s no way that boat planes at 2000 rpm. My boat does, but it’s a bit of an exception to the general rule. She will sit nicely on plane at around 2100/2200 at about 25-27mph. But a bit of a special thing. Which boat do you have that will plane at 2000 rpm. It must be some machine and I would say we are in the minority for sure.

 

[QBhoy]

My boat planes out at 1700. Makes it really tough to pull newby wakeboarders that want to go 17 MPH. Not that I disagree it's the tach, just not true that no way does a boat never plane at 2k.

It must be seriously propped on the high side like mine too. High power to weight ratio you have I’m guessing Rick.

 

[Rick Stephens]

It must be seriously propped on the high side like mine too. High power to weight ratio you have I’m guessing Rick.

If I stick the throttle at 1700, the boat will hang there for a few seconds, then roll up into plane and speed up to just under 20 MPH. A couple reasons for that. The boat is smallish at 17 foot. I added a bunch of decking, made it a fishing barge with a deck in the bow containing built in live well instead of typical bowrider seating. So it isn't really light. Of course, it also upgraded to the V6 with almost double the horsies. I run a fairly steep 23 inch 4 blade since I don't need high end speed. And lastly, I installed Smart Tabs and have them at highest pressure setting. Prop and tabs give me tons of stern lift. Wife loves it, like having shock absorbers when crossing wakes. Boat basically gets 1 MPH per 100 RPM. Be a bit faster with something like a 25 inch stiletto prop, possibly.

 

[QBhoy]

If I stick the throttle at 1700, the boat will hang there for a few seconds, then roll up into plane and speed up to just under 20 MPH. A couple reasons for that. The boat is smallish at 17 foot. I added a bunch of decking, made it a fishing barge with a deck in the bow containing built in live well instead of typical bowrider seating. So it isn't really light. Of course, it also upgraded to the V6 with almost double the horsies. I run a fairly steep 23 inch 4 blade since I don't need high end speed. And lastly, I installed Smart Tabs and have them at highest pressure setting. Prop and tabs give me tons of stern lift. Wife loves it, like having shock absorbers when crossing wakes. Boat basically gets 1 MPH per 100 RPM. Be a bit faster with something like a 25 inch stiletto prop, possibly.

Sounds a good set up rick. My fastest boat (that’s running at least) is really heavy for an 18 footer, but an apex stepped and pad hull helps it out, along with about or just over 300hp I suppose. Useless out the hole but gets going at the top end and cruises really well.

 

[JonBoat55]

Thanks...worst part of being new with something is not knowing what you dont know. I was looking and stressing over at the WOT RPM sticky and it seems its just a gauge problem.

Whats the procedure of checking throttle cable settings if I wanting to look into that?

 

[THenning]

What shop tach's do you all recommend while we are on the topic?

 

[Rick Stephens]

What shop tach's do you all recommend while we are on the topic?

I use a decent digital timing light with an electronic advance.