Dt100 water under cowling

[Tim dt100]

As the title says, I'm having trouble with water appearing under the cowling of my 1993 Dt100! When I run on muffs or in a barrel I can't find any sign of a leak.
When I'm on the water and run at around 1/2 throttle and on the plane there doesn't seem to be any water under the cowl. BUT once I Ron at WOT even for a short time the water is entering under the cowl quicker than the drain hole can get rid of it. I've not had a chance to run it on the water yet with the cowl off, that will be my next test. I've also removed the plastic cover covering the drain hole but yet to observe while on the water.
Have any of you guys had similar problems or maybe be able to steer me in the right direction. I've not had the boat and engine for long so don't know it's history, the tacho didn't and still doesn't work, i did one day try to pressurise the pilot hole to test the guage but could only get it to work when I disconnected the pipe at the bottom of the leg. Is there any way that pressurising the pilot hole could be causing my problem? Just not sure that the issue was there before I messed with the tacho!
Thanks in advance for your input.

[Solarman]

True on the knowledge part.
It is important to find out where the water is leaking from. Your best approach is blow dry all areas under the cowling completely. Then in run in a tub with good lighting to see where water shows up first.

If you're running with the pitot tube for the speedometer that tube usually doesn't go into the cowling on most models? If it does on yours, it is possible it could leak water at higher speeds (more pressure). Water pressure is all that pushes the air in that rubber tube to cause air pressure to move that speedo. If that tube leaks you won't get pressure to the speedo.

With the amount of water you're talking about, it should be easy to locate where it is coming from. Also, if it only leaks in the lake while running, disconnect the speedo tube outside the motor and plug it. Then run the motor in the lake, if no more water, speedo tube might be causing the problem.

Post back what you find out. Good luck.

[Tim dt100]

I don't reckon the pilot is to blame but I'll get a look later, it only seems to leak when at speed, I can't get even a drop to appear when running in a barrel? Very strange, can't wait to get to the bottom of it!

[Tim dt100]

You were correct, the pilot tube doesn't enter the cowling, I've ran the engine in a tub with the tell tale directing back in so as to recirculate. I ran until tell tale water was luke warm and could feel the heads getting warm, water circulating throughout the engine but still no sigh of a leak. I'm no stranger around engines having 20+ Years experience in the motor trade and been around boats for most of them, I'm going to have to get back out on the water with the cowling off, was just Hoping somebody on here has had a similar problem and may be able to help. I'll post what I find!

[Tim dt100]

Finally found cause of water ingress

I know it's been a while but I have only managed to get out at the weekend to test my repairs! If I can I will attach an image of the part that was missing.
It was a small rubber tube that connected the drain tube to the lower unit, with this missing the cavity would fill under pressure when at speed causing a fountain of water to be ejected from the drain hole under the cowling and flooding the engine!!
A cheap fix at £3 and after a full service and trailer service I'm looking forward to a trip to the Isle Of Man to watch the TT races in June

If the pic uploads the part that was missing was no.4

[Solarman]

Thanks for posting your repairs. It has been awhile.
Happy boating.