New to me '89 Formula 242 LS.
I have a water leakage problem that I can't find. Water is only coming in while the boat is in motion. While sitting still, engine off or engine on, there is no increase in water level. I've sat in the engine compartment to verify this (watching exhaust, water pump, transom plate, etc.). The boat has sat on the hook overnight and no increase in level. Take it for a run and the water level increases. (So far, I've had no volunteers for sitting in engine compartment while boat is in motion!!) The hull is in good condition, so I've crossed that off. I suspect the problem is related to the outdrive. (Boat has the silent thunder thru hull system.)
Has anyone experienced this or have any suggestions?
Thanks,
Kevin

If the leak only occurs while in motion, I'm afraid you'll need a volunteer to sit in the compartment.

many years ago my dads 1963 36' Chris Craft had a leak like yours that only showed up while moving. I sat in the engine compartment (cockpit deck hatches open) with a flashlight while both 327's were running. I crawled all around watching everything. Sure was loud down there.
The leak turned out to be a hull plank that needed re-caulking.

How about a cheap 8mm video camera braced in the engine compartment, that is if you have good lighting in there. Do it several times from different angles to catch all areas that could leak.

How much water are we talking about? I assume that there is no more water when you are running the engine in neutral?

Most likely thing after that could be the speedo tube is leaking, does the speedo work?

Safest way to check for other leaks would be to remove the hatch then go for a run.

Running engine in neutral doesn't add to water level.

Speedometer works. A transom mounted pickup was added. The tube from the outdrive is routed to the new pickup.

this is gonna be sorta messy but it will work......dust the engine compartment in baby powder or even jello mix....then go for a run and see where its wet....then hose it all out and clean after you find the leak

Done the baby powder thing before in cars. It works.
Save the jello for making shots.
Gary

Don't quite understand this,

You have both pickups teed into one feed to the speedo?

Is this done inside or outside the hull? If outside, then you still have a hole through the transom assembly where the speedo tube comes through.

Wobble - the tube that normally would attach at front of cavitation plate (on drive) has been extended/relocated to attach to transom mount pick-up. Don't know why prev owner did this.

I had this same problem not once but twice, and it was the speedo hose. Wipe dry and then take a quick run and back to inspect hose for wetness. Propwash f311.