Aq130c / 270.

I have hardly ever had the chance to use my Draco 2000DC due to a succession of problems that it was very, very difficult to find someone capable / reliable to fix! Now that I have (in a choppy Solent) she got to 4000rpm and almost got to plane but I noticed the temperature go almost into to the red (slowed down immediately / gave up). It recovered OK (although the crankcase breather rubber pipe obviously got very hot and changed colour) and I remember reading on here about the possibility of an air leak on the small hose between the transom shield and leg. What is the best method to test this (preferably while she's still in the water)? Many thanks,

How old in the raw water impeller? If new and you are sure nothing else is wrong.. to test for vacuum leak.


Buy a short length 6in to a foot of clear plastic reinforced hose the same diameter as the raw water line.
Buy a hose joiner of the proper diameter and two hose close clamps
Disconnect raw water hose from inlet of raw water pump keeping it as high as possible ( lest water come in the boat)
Connect the clear plastic hose you bought to the raw water line using the joiner and clamps.
Connect other end clear hose to pump.
Secure all clamps.

Start and run engine in neutral, hose should have no air bubbles. Take boat out and as the boat gets on a plane, you may see air bubble in the clear hose...

The Vacuum leak is usually only apparent when the boat is on a plane or nearly so. It is caused by a defective fitting at the point where the raw water "S" line attaches to the drive... usually... or a collapsed "S" hose ( between drive and transom shield)...

Hi, thanks for the response. The boatyard are now pretty sure there's an air leak at the transom shield / stern drive. However, they've also done a compression test and it was low. The head is now off and looks OK but the block has corrosion and they don't want to risk re-using it! Is the block itself the same as the B20 car engine (mine is 4929)? There might be more chance of getting a car's block. Many thanks once more. SA

Air leak... most likely at the fitting on the drive that the raw water hose attaches to... It's prone to corrosion/pin hole leaks..
I solved that and other problems by going thru hull with an external wedge shaped strainer. Added bonus : plumbing a T at the thru hull for flushing and winterizing. See PM