Tango repowered

[Rapier]

After my winter disaster with Tango's '69 Merc 500, I snaffled some 'modern-ish' and rare shortshaft power with a view to us getting up on one waterski instead of dropping / jump starting. After a few days graft to sort out the carbs, remotes and wash the sand from the cowling's foam (!)+ lots of help along the way (why does rigging always take so much time?) it is ready for a test tomorrow. I view it with some trepidation; even if I know the Thunderthingys can handle much more hp, the handling does suffer. Having run powerhead rated Merc 350s, a 500 on mine and taken a drive in Moonman's 40hp Evinrude powered original I'd say the 50 Merc is probably the best all rounder, with 35 mph and the ability to pull a 70-80kg skier.

[Rapier]

Bought this tacho and have hunted high and low through my 1300 page Yamaha manual for a wiring schematic to work out where the yellow wire connects

On the back of the gauge are 4 terminal posts labelled 12,B,6 and G.

2 black wires connect to B, one is cut (assume it runs off to supplementary gauges and is unnecessary?) There is a terminal bridge from B to 6.

2 green wires connect to G, one has a female connection and I've assumed it's supplemental.

1 yellow, 1 green and 1 black connect to the tacho loom off the back of the Yamaha 703 remotes.

The cut yellow wire has a 10A inline fuse...and I assume is the ignition feed..to where?

Can anyone help?

[solitaire]

Nick - is this any help

http://www.maxrules.com/fixyamahawiring.html

anything black to ground
anything yellow - to ign on (back of ign sw) - surplus - (non fused) yellow probably intended for other inst's
Green - tacho signal

[Rapier]

Used Maxrules before, his site is great for Merc stuff too.

The yellow wire (with fuse) is on the tacho side loom rather than the control box side, so it must connect to the gauge somewhere?

[Rapier]

Took the boat out to Calshot with a full load of family, fuel and other sundries... then went up and down a very choppy So'ton water for an hour or so - huge swells come from nowhere - ran at between 20 and 35 mph. It goes well once over 8-10mph throttle setting, but it sneezes at idle and sounds like one pot is snoozing sometimes - I opened the mixture screws to 2 1/2 turns out, but it still fluffs through a 10 mph throttle setting.

Will strip carbs again tomorrow and see if there's something I've missed. Will check with the Merc tacho when finished - hard to judge RPM under load, but I may be able to get close enough. Goes very well otherwise - nicely quick, but not with a full boat and the chop. The autolube works fine (I had 100:1 premix in the tank, in case..) and is reasonably frugal on fuel too. we shall see.

[floater]

Appreciate mine is a totally different motor but I had a similar problem, it would idle well but as you open up speed would increase up to the point that the butterfly's start to open then it would die. If you whacked it open from idle it would take off fine. I played with the idle screws but that didn't get it. I changed the carbs for a spare set and all now seems well so I guess there must have been dirt somewhere despite my cleaning and doing a full carb service kit.
On the other hand is the fuel pump and primer bulb ok? perhaps it runs weak slow but at higher revs the pump is coping better.

[haventaclue]

Possible powerhead to leg gasket ? Maybe a bottom crankcase seal going ?

[Rapier]

Crunchy, but tasteless piece of something blocking the main jet of the middle carb - they were very dirty before I stripped them initially, so may be something that's worked it's way through. Dodging showers here and the Sabbath, so looks like I'll only be able to fire it up tomorrow.

Stripped the foam from the lid too, couldn't wash the fine sand out that was in it - looked like builders sand. Not a good idea near the carbs either.

[floater]

Sounds like the culprit hope all is now well for Falmouth.

[Alacrity]

Good-oh, fingers crossed Tinbum.