Bad switch box?

[coffeeguy]

91 200 efi analog box(isgood) Rebuilt first lake test. Timing set at -4 * at idle and 22 at wot. Compression 124/125 across the board. 93 octane. Boat idles fine but can't get on plane . Heard a bit of detonation. Falls flat on its face between 2&3000wont rev until prop cavitates. I am suspecting a bad switch box. At what rpm does a bad switch box show itself?

[j_martin]

'bout there.

[bullet123]

Could be stator

[coffeeguy]

All stator test numbers came in spec but over 3000 it drops the 2/4/6 side. Will try new stator tomorrow. Can one side of the high side of a stator go bad?

[bullet123]

Yeah. Sounds like high side took a sh it

[Motv18]

Does it rev without a load?

if it does it could be fuel side, occasionally the injection is controlled by separate things at different rpm that’s also the sweet spot for that malfunction.

But its it’s more likely the stator switchbox

[Stoker boy]

Having pyros and indexing your fly wheel would be a great help to diagnose the problem.

[j_martin]

Does it rev without a load?

if it does it could be fuel side, occasionally the injection is controlled by separate things at different rpm that’s also the sweet spot for that malfunction.

Naw, it'd rev on a couple of cylinders on the hose. Could be stator or switchbox, with stator most likely, especially if "good" test numbers are the resistance numbers. Cold be breaking down at temp. Same is true of the switchbox, that is something breaking down at temp.

[bullet123]

I agree

[Merc 2.5]

Swap boxes around and c if it happens on 1,3&5

[j_martin]

Maybe easier to just swap stator wires to the switchboxes.

[bullet123]

[XstreamVking]

What about the regulators? Can they not mess up the stator? I believe a test is to disconnect them one at a time and test run...(Yellow wires)

[Forkin' Crazy]

Have you run a spark check? All 6 at 7/16"? Other wise bad stator.

[Motv18]

The rev with cold start is just an old ear test and friction check. If it revs but drops cylinders start with switch box and it’s probably not fuel. Doesn’t really prove one thing or another but will show component fail is not load related.