V4 130hp high rpm misfire

[Corkster]

My 130 used to rev cleanly through to 5800rpm which was top speed for my boat/prop combination. On a recent trip it suddenly started to misfire at full throttle 5500rpm but starts and runs perfectly otherwise. The misfire almost sounds like a rev limiter. I have tried the following so far with no success:

New fuel pump
Alternative portable tank
New plugs
Check timing
Strip, clean and fit new kit to carbs - they were clean inside any way
Compression test - even comps at +-120psi
Coil and lead ohms checked out

Any ideas?

[rodbolt17]

did you check CDI output and timing at the misfire RPM and load>?

[Corkster]

No I haven't, how do you do this safely? Run the boat on the water with the cowl off and flywheel exposed? Sounds a bit hairy!

[99yam40]

run some test leads out from under the cowling to a place that is easy to get to and read