Tachometer for 1978 Mercury 500 Thunderbolt

[lgaytan]

Hi,
what kind of tachometer I need for my outboard? 1978 Mercury 500 Thunderbolt 50HP S/N
4967035, after some tweaks I think it is running good but even being a small engine it is a thirsty one, it consumes too much gas to what I believe should be doing, we usually go WOT I want to change that and find the cruise speed, having a tachometer I believe will help.
Last trip I estimate we traveled 33 miles total and consumed almost 10 gallons of gas. We were 3 adults, a full 40 qt cooler, a 20 pound anchor and some fishing equipment, I don't think we were specially heavy. Anyways, what tachometer do you suggest?

Regards

 

[racerone]

What size boat ?-----How long did trip take ?----Check fuel pump diaphragm ??

 

[Scott Danforth]

You should be burning about 25 # of fuel per hour with a 50hp 2-stroke

You will burn more getting up on plane

 

[1960 Starflite]

You'll need a tach driven by a signal from one of the yellow stator wires.

 

[lgaytan]

The boat is 15' long, I'm unsure of the lenght of the trip but we were running average 25-26 mph, that means that over all it was 1.3 hours more or less. According to what I have read the rle of thumb is that my 50 hp will burn 5 gph. It should had been 6.5 but we burned 10. There are things to fix still, I noticed that the hull has a crack and water is comming in there's more weight there.
Have you tried the tiny tachs? are those reliable?

 

[Scott Danforth]

Tiny tachs are ok. However any outboard 2 stroke tach will work

What speed does your boat plane at? If you hover around that speed, you will burn more fuel than you would at WOT

 

[lgaytan]

not sure what is the plane speed, how can I check this?

 

[Scott Danforth]

not sure what is the plane speed, how can I check this?

At what speed does the boat come out of the hole when you take off? Should be about 12-15mph