Think my tach is wrong.

[Les Young]

What woulb be a good one to get to go on my 1992 70hp Johnson & also be easy to install. I'm trying to find a prop & don't think my tach. is right because a 13&1/4 by 17p turns 5900 rpm & a 13x19p turns 5800 rpm Thanks

 

[Bifflefan]

Re: Think my tach is wrong.

at what MPH?????
the boat is going faster with the 19. but with out the MPH there is no answers.

 

[Les Young]

Re: Think my tach is wrong.

Got 38.6 with the 17p & only 36 with the 19p

 

[Bifflefan]

Re: Think my tach is wrong.

got me stumped then.
PM hwsiii he knows everything about props and why they work or dont.

 

[billy4hp]

Re: Think my tach is wrong.

What woulb be a good one to get to go on my 1992 70hp Johnson & also be easy to install. I'm trying to find a prop & don't think my tach. is right because a 13&1/4 by 17p turns 5900 rpm & a 13x19p turns 5800 rpm Thanks

So why do you think your tach is wrong? The greater pitch caused the RPM to drop. I would have expected it to drop more than 100 rpm, but are both props from the same manufacturer, same series, same blade count, etc?

If your original prop is 13 1/4 in diameter and the replacement was 13 diameter then the 100 rpm drop might be correct...

As previously mentioned, I would post this in the prop forum rather than here, hwsiii checks that area often and really has a good insight on props (as do some of the other wise men that post there)...


Good luck...

 

[countvlad]

Re: Think my tach is wrong.

What woulb be a good one to get to go on my 1992 70hp Johnson & also be easy to install. I'm trying to find a prop & don't think my tach. is right because a 13&1/4 by 17p turns 5900 rpm & a 13x19p turns 5800 rpm Thanks

is the tach settings/poles corect? going from a 17 to a 19 i think you should've seen more RPM drop... but this is what you can do just to eliminate the tach posibility

for a water cooled rectifier:
http://forums.iboats.com/showthread.php?t=190636

or a small 3 wire rectifier"

http://forums.iboats.com/showthread.php?t=190638