This 1976 Merc 500 was a purchase last year - rare for a clean freshwater short shaft engine to pitch up on ebay so I took a punt. Newer ignition than my '69 on Tango - think may have been slightly longer shaft and redesigned gearcase - maybe the experts can advise.... Nice and clean under the wrap and no evidence of the baboon spanner brigade, bar red hermatite on the plastic pump cover, which is likely warped. Today spent setting it up for electric start - will be both manual and electric. Took the ring gear off another scrap flywheel - which had shims..no idea what it came from - welded it on to mine. One negative starter brush was a dud, so it didn't work 1st time. 4 bright sparks and decent compressions on all 3 top pots - will check bottom with short Merc compression tester tomorrow, followed by a service if all goes well...

Obviously staged in colder climes..

Fired up today, on no2 spark on tester, no spark on load. Took the carbs apart and cleaned them - the baboons had been there, the tang carrying wiring was under the carb, i.e. gasket, tang, carb, bolt. The bottom carb had no gasket and leftovers of the gasket to draw air in. Alacrity advised a coil replacement which thanks to his sharp eyes at Beaulieu Boat Jumble (@ £5 each..for NOS!) Quick change and problem solved. Dropped the box -nice clean freshwater motor, impeller is set and housing dented for some reason - hope to replace that tomorrow. Rain, a bitter wind coming from up river and 5 degrees outside today...still thawing out. Happy days.

Great news, are you planning on putting it on Tango?

Yes, that was the thought...better ignition, e/start, better water pump and variety of 13 spline props - I can put my pressure gauge on it too. Frustrating day, as it took ages to mate the gearbox and it sounds like it needs an upper crank bearing - will post a video later for you experts, but it rattles like hell at idle and despite a good look at the flywheel can find nothing amiss. I didn't notice it yesterday, but didn't run it for long...

Vid from today..

Take a good look at the flywheel flexplate, they do crack quite commonly on that engine. Crank bearings are not to hard to replace but if it was mine I would pull the powerhead off and split the crankcase for a lookie see. Not as bad a job as you might think!

Thanks George - Geoff said the same, so will take a look when it warms up here - we're having unseasonably cold weather. Still thawing out from my sojorn in a mate's workshop last week.

After 4 years I finally got back to this one. Having found a proper flywheel for the motor on fleabay I swapped them over and torqued it down. A set of fleabay aquired carb fuel pump diaphrams were installed and the starter motor bolted back on. Motor was spinning, but was very lazy under load - having run this years ago and put it away after I wondered what had gone wrong in the interim. Serviced the starter motor, without any joy under load and had no means of checking the amperage. Off to the outboard shop with it and realised we'd fired it up there with the jumper box and a remote key switch and the likely culprit would be my leads - came back home and set it up on jumper cables and it worked spot on.

Cut the leads open to have a check...they are Yamaha leads (more flexible than most manuf) and were a used auction site purchase, albeit for not much money. The pictures show how bad they are - a case of buyer beware. The shop is making up new leads for me.

Having fired it up, it's running on 3 again - I think no1 is the culprit, but my Mercury analyzer 'suitcase' will come in use to run the diagnostic tests needed for these models.

No spark on no1 & switchbox at fault - pity as the rest of it tests out fine. Am a fan of these modern ignition motors, but they do manage to pack a lot of circuitry into them. Luckily the shop is open tomorrow and am sure I'll find a few used ones in the parts pile, maybe find two...