Mercury 75hp 4-cylinder 2-stroke oil mixture and other questions

[Jerax]

Hello,

first i'd like to introduce myself since i'm new to this forum. My name is Jörg and i'm from Austria, Europe. I'm owning a boat since three years now and recently upgraded to an old Elan Boat with a 75hp Mercury outboard.

Although i do own a service manual there are several questions that are not mentioned there (and it dont have a regualar users manual)

Firstly the engine is supposed to be a 75hp 4-cylinders. So it should be model year 84-86 although i couldnt assure this with the serial number as it doesnt fit with any of the references found on the web. (Serial is 9453658)

My questions are:

1.) can anyone confirm that it is the engine i think it is?
2.) what's the proper oil/gas mixture - previous owner said he used 1:25 but that seems a lot to me considering the supposed construction year
3.) what is the current output of the power generator/coil on this engine (i'd like to operate a fairly high powered hifi an dont want to drain battery)
4.) there's a problem with the rpm-meter. The instrument in the dashboard seems to work (needle moves for a moment when main power switch is closed) but it doesnt show the revs of the engine. where/how would i best start to search for the cause of this issue?

Thanks in advance for your Feedback

best regards

Jörg

 

[Texasmark]

1. For years 2 cycle (stroke commonly used term today) engines in the marine industry used a 1 part oil to 50 parts gasoline, called 50:1.

2. Doesn't really matter from that standpoint as regardless of hp all engines ran the same ratio.

3. Biggest alternator available which is red, looking under the flywheel to see the color is 16 amps. 16 amps x 12.5 volts is 200 watts not counting losses along the way. Don't expect it to produce that kind of output continuously. That is the max rating and when thinking of charging a battery, it peaks and then as the battery charges, it drops off allowing everything to cool and that doesn't happen continuously in the mind of the designer.

4. Several problems could be associated with your tach; bad rectifier regulator, dirty contacts on either the rectifier regulator or the tach, bad tach.....

HTH,
Mark

 

[roscoe]

Welcome to iboats, Jerax.

Your motor is indeed a 1986 model.
Manufactured in Belgium, not the USA, that is why the serial number doesn't fit the reference.

75

4-cyl

9444516

- 9466566

1986

Belgium

Yes, 1 part oil, 50 parts gasoline.
20 ml oil per liter of gas.