Tach reading

[crownroyal]

First of all great message board... I have a 1988 johnson 60 hp 3 cyl. motor. It runs just fine but the tach reading is reading at 1400 rpm's at idle and WOT it reads at almost 7000 rpm's. Question...is it worth adjusting this tach or better off buying a new one.. Thanks<br />P.S. the prop on this motor is a 13 3/8 X 17 pitch on a 16 foot bumbleebee bass boat running about 40 mph top speed

 

[R.Johnson]

Re: Tach reading

What make is the tach, If it's an OMC there should be a pulse setting on the back side I think the setting should be 6 on your engine.

 

[crownroyal]

Re: Tach reading

Its not an OMC tach. Its reading almost 7000 rpm's at full throttle and the reading is id say 15% off. Probably be better off with a new tach huh?

 

[rickdb1boat]

Re: Tach reading

Did you look on the back of the tach and see if it's set on "6"? Did it ever read right?

 

[crownroyal]

Re: Tach reading

Rick,i'll try that tomorrow,thanks

 

[crownroyal]

Re: Tach reading

Looked on back of tach. Theres a rubber washer that says cal next to it. Took it off but just a hole. Below that is a setting that is pointing to the number 1. It can be set at 1 2 3 or 4. High as it goes is 4

 

[rickdb1boat]

Re: Tach reading

I am not sure which setting would be correct on that tach. You could try different settings and see which one works, if at all. I would try the 4 position first. You would need another borrowed tach to confirm the readings are correct, especially at full throttle. If all this fails, I'd pop for a new tach that has the correct pole settings available. They sell them here on I-boats and others. Teleflex is a common brand, which will work.<br /><br /> web page<br /><br /> web page 2

 

[crownroyal]

Re: Tach reading

A 1988 60 hp johnson 3 cyl. is a 2 stroke isnt it??

 

[rickdb1boat]

Re: Tach reading

Yes, it is. I have a 91' 70 HP, which is basically the same thing...

 

[Hooty]

Re: Tach reading

That may be the wrong tach for that engine. Has it ever worked right?<br /><br />c/6<br />Hooty

 

[crownroyal]

Re: Tach reading

I dont know ,i just bought the boat,it runs great but the tach i know is giving a false reading. Its idling at 1500 rpm's by the tach but theres no way its idling that high. Half throttle it reading almost 6000 rpm's... Whats the main thing to take in consideration when buying a new tach???? Thanks

 

[VistaMan]

Re: Tach reading

The switch on the back of the tach typicaly shows 2P, 4P, 6P. this is the number of poles in the alternator. I think for your motor it should be set to 6P to read correct.

 

[crownroyal]

Re: Tach reading

Its the wrong tach then,it only has the numbers 1 2 3 and 4. It was set at 1 i adjusted it to 2 and 3 and it was idling at 5000 rpm's. Someone a few posts back gave me a link to a tach im gonna buy.

 

[ob15]

Re: Tach reading

Could go with a tiny tach too. I jsut put one on my baot & it works great. www.tinytach.com