1990-2150 XLC-Taking on a lot of water-Please Help!
 

My family recently bought a 1990 21' Mariah Cuddy with a 5.0L V8 Mercruiser inboard engine.

The boat sat in a warehouse for 4 years before we bought it. It had been winterized prior to being stored. The boat is in very good condition given it's age.

The first time we took it out we notice the bilge pump coming on after running down the lake or when pulling a tube/skis. The bilge pump would take out ~2-3 gallons of water after each time we would get up to speed and come to a stop. Obviously this concerned us, being that taking on that much water that rapidly.

We checked to make sure the plug was 100% secure after putting the boat back on the trailer, it was tight and not leaking. After taking it to the local boat mechanic they said that all the seals and bellows looked and tested fine, and swear up and down that's not the problem.

Long story short, the mechanic can not find the problem (after several visits) and we are out of ideas. We have had the boat out two times since and it does the same thing, sitting still at the dock little to no water comes in, from starting to about 2 hours in there is little to no water, but after a few hours of running we start to take on the amount mentioned above.

We are stumped...Any help would be greatly appreciated. We are new to boating and may be missing something obvious.

I should mention that our boat has a shower system on the swim deck that we have disabled at the shower end, the water pick-up under the boat is open, the mechanic has looked into a leak on the internal plumbing to find nothing.

Re: 1990-2150 XLC-Taking on a lot of water-Please Help!
 

Could it be a leak in a water inlet pipe, when you're running at higher RPMs, maybe a line is leaking from the added pressure. Or maybe it is a line after the thermostat that is leaking, so it doesn't leak untill the thermostat opens...

Do you have a fresh water tank? Maybe there is a crack in that, or a break in a line that is leaking, or spilling when you're getting out of the hole. I would check these things first.

The bilge in our boat only comes on when the ice starts to melt in the floor cooler.

I would also find a different mechanic that will find the issue. There still could be a leaky bellows, or something...

Re: 1990-2150 XLC-Taking on a lot of water-Please Help!
 

Well, I was noticing just a tiny bit of water on some trips and not others. By chance, I was watching the engine running, and notice the water pump shaft seal on the front of the engine was leaking. Can't blame it after doing its job for 14 seasons without any problems. Sometimes seals will leak, then swell and stop, then start again. Or the water could be from a cracked or loose coolant hose. Just some things to check besides the plug & bellows.