1978 Johnson 115hp Starting issue on water

[Blackbox]

Hi all,

Wondering if anyone else has had this same issue and how they fixed it.
I have a 1978 115hp 4cyl which starts up great on the driveway within one or two turns of the key but when on the water its a real pain to start. Can take 10-15 goes to start and sometimes won't start at all. One way I have managed to start it on the water is by tilting the engine all the way up and starting out of the water then putting straight down again.
Idles fine and runs well out on the open.
Same issue when starting warm or cold yet after a day on the water and back home its starts first time on the driveway when flushing out.

I have new spark plugs, overhauled the carbs, checked compression 110,110,115,120, fresh fuel, firm bulb when starting, new power packs, new thermostats and cleaned out all salt build up in tubes.

I know its an old engine and 2 strokes can be a pain to start but this seems beyond normal starting issues. Any ideas where to do next

[Joe Reeves]

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(Engine Won't Start or Hard Starting In Water)
(Joe Reeves)

The Evinrude and Johnson engines, starting in 1973, have what is called Magneto Capacitance Discharge ignition, self contained, not dependent on battery voltage. The engine must turn over at least 300 rpms in order for the flywheel magnets rotating past the stator ignition generating coils to supply approximately 300v AC to the powerpack(s), which in turn is needed to supply power to the coils etc etc (spark).

In the water, exhaust back pressure is encountered due to the fact that the exhaust housing (housing between the powerhead and the lower unit) is filled with water. This would drag down the needed rpms, affecting ignition.

Normally the clue to this type problem is that the engine starts fine on a flushette (hose), but is very difficult to start when in the water.

Should this be the case, check the battery, clean and tighten all conections (use a wrench or pliers, not your fingers). Any cable that gets overly warm or hot indicates either a loose, or tight but dirty, or internally corroded cable. And of course check the starter itself.

[Blackbox]

Thats great information, thanks Joe.
Battery is pretty old so will get that tested as all the connections are good.
Thanks for the help.