Mercury 50hp Charging and IDing

[ronsealdeath]

Hi there,

My Evinrude 55hp has gone with my 14ft speedboat and I am now the proud owner of a 17ft fishing boat with a 50hp Merc 3 cylinder 2 stroke.

The engine had an 'auto blend' box on which I have disconnected to use 50:1 premix instead. Assume this is ok to do?

The serial number is hard to read as its been stained by something but looks like 3 numbers maybe 144? then 613246. Anybody got any idea what year this motor may be and if 50:1 is the correct ratio? Can I ID the motor any other way?

Also, would I be ok to hook up two 75ah leisure battery's on the charging circuit using one to crank and one for the lights, horn, ciggie lighter etc...... I am not that familiar with electrics; would the outboard be able to charge the two batteries ok?

Also, I noiced the plugs were of a strange variety with a stubby little electrode on them. Does it arc to the piston or something?

Cheers
Al

 

[Silvertip]

Re: Mercury 50hp Charging and IDing

Your engine has surface gap plugs. Been around for decades. They do not fire to the piston. They fire to the metal side of the plug just like a regular plug. There was no need to disable the oil injection if it was working. It is a reliable system. The engine has a 16A charging system. Use the SEARCH feature to lean about DUAL BATTERY SWITCH, VSR, etc. None of the stuff you are powering draws much current so use of two batteries is not necessary. If you do add another battery, it will take twice as long or longer to top off both of them than it does just one. And the alternator puts out maximum current only at wide open throttle. So you would need to run wide open for long periods to charge even one deeply discharged battery.

 

[ronsealdeath]

Re: Mercury 50hp Charging and IDing

Thanks. The reason I mentioned the two batteries is because it came with 2 nice leisure batteries but they were hooked up for one to power all the aux equipment and one to crank the motor. The seperate one wasn't connected to the charging system so I figured an isolator/selector switch would do the trick. They are expensive things from looking at them! Maybe I will keep the system as is and just charge the aux battery with a plug in charger at home after we have been out in the boat. That is unless I can get a switch for a good price.

I know disconnecting the auto mixer wasn't necessary as its done its job for a long time with no issues. I just got pressured into doing it by reading about engines failing from the system not functioning properly and the loom from the engine to the alarm system not coming with the boat. Its interesting because the system feeds oil at a variable rate to the motor according to the manual so by pre-mixing I am perhaps giving it too much oil at idle and low speeds? I can always re-fit it as it its nice not to have to mix the fuel. Any opinions on whether pre-mixing at 50:1 is not as good for performance as the blending system?

Cheers
Al