1984 Mariner 50hp Tachometer and RPM questions

[mkrussow]

I have an '84 (may be an '85) Mariner 50hp. It's a 4 cylinder.

I've had this motor for many years, but have never had a tach. I've now installed a tach and have a couple simple questions that I'm struggling to find answers for.

What is the recommended WOT RPM range for this motor? I've never really done any work to optimize the prop on this boat and would like to do that.

How many poles (pulses) does this motor have? The documentation that came with the tach isn't very clear to me. It appears the motor has 8 poles, so the dial on the back of the tach would be set to '4P'?

 

[jhow0228]

Re: 1984 Mariner 50hp Tachometer and RPM questions

It looks like WOT rpm range is between 5k and 5500. As for the other question, I have no clue.

 

[mkrussow]

Re: 1984 Mariner 50hp Tachometer and RPM questions

Thanks, jhow0228. Hopefully I should be able to figure the tach setting with the motor idling and then I'll have a target to shoot for on the top end.

 

[oldman570]

Re: 1984 Mariner 50hp Tachometer and RPM questions

WOT is 5000-5500 and the stator should be 12 pole with tach set at 6 for your motor. You will need to buy a wire harness that goes from the throttle controller to the dash that will plug into the control and supply battery + &- along with tach signal and connect the gray wire on the motor to one of the yellow wires on the rectifier to get it to work.
You will find a manual for your motor at
Boatinfo - Mercury Service Manual for 30jet-40hp 4 cylinder
JMO
Oldman570

 

[mkrussow]

Re: 1984 Mariner 50hp Tachometer and RPM questions

Thanks, oldman570. I had the tach set at 4P, and the RPM's didn't seem quite right.