New thread about 1978 70 HP Mercury outboard

[j-bg00d]

Hi guys!!

I still have that good ole 1978 70 HP Merc Outboard.. with a problematic shifter..

The prob I'm having is that when using the shifter throttle in either forward or reverse you have to also have to manually use the warm up throttle lever at the same time (the 2 hand method ) to get enough gas to get the motor to perform. It still wants to hesitate and stall under load when not using both levers.

Its almost like they are not aligned or syncronized to work together..
Its a head scratcher .. I bought this boat set up a while back, and this has kind of been an issue since day one for me.

Now since this thing is definatly not new and has probably seen a few repairs in her time; I wouldnt know WHO has done WHAT to this ole motor over the years..

Anyone have any ideas? I'd def welcome some input..
I'm going to take the shifter apart and look for anything inside that could be broken or loose i suppose.. and go from there..

Thanks
J

 

[fastjeff]

Your idle mixture screws may not be set correctly (which is very hard to do on these motors) or it may simply be idling too low.

I use an infrared heat gun to adjust these triples, using the metal shell of the plugs for the target of the dreaded red spot. The trick is to get all three plugs the same temperature. The motor has to fully warmed up and idling about 1,000 rpm. Expect a surprisingly cold temperature--usually around a hundred degrees.

Jeff

 

[j-bg00d]

Thank you veey much for that reply..
Sounds pretty high tech.. I don't have that kind of device to check the heat..

I was kinda leaning towards the shifter cables not being set up the way they should be.. it idles not to bad all in all..
And the reason I think that is because the warm up throttle pulls itself up o 've you mac out the forward or rev gear throttle..

 

[j-bg00d]

I am not to sure I understand how to get all 3 plugs around the same temp?? how do you adjust a spark plug temperature?

And

Is it normal on the Control box "shifter" that both handles move when throttling up? I was under the impression the little one stays down once you take off in either direction..

 

[haventaclue]

Something is binding up inside the control,Possibly the throttle roller is not in its place,the roller you see in the throttle half should fit into "G" on the shift side