I have a 2000 Donzi 28ZX with twin 350MAGs.

We took it out last week and blew a hose off the port motor (water pump outlet hose). We figured it was a faulty hose clamp so we replaced all the hose clamps yesterday morning and went back out.

Pop, hose blows off again. Now we're thinking the expander hose it too short and we'll have to replace it. We reset the hose, torque down the clamp a little more and head back in. About 1/2 way we stop to check it out and the hose is creeping off, but not all the way off yet. Reset it and continue heading back in.

Bilge alarm starts going off, we figure we've blown another hose so we open the hatch. Now there is a 4-5inch long gash in the water inlet hose (it's burst). We weren't overheating.

I didn't have any problems with the boat until a certain mechanic worked on it. He replaced the thermostats and impellers.

What should I look at first to diagnose the root cause of this? Has anyone had similar issues?

Something is causing water pressure to be way high. Clog in the system (is it a salt or fresh water boat, riser could be blocked). Did all this start when thermostats were replaces?

Almost makes you think the thermostat might be in up side down. Did you happen to noticed the hose getting bigger while running. Did it seem like it took a little longer or slower to get to your normal engine temp. Just guessing.

Yeah, my friend and I were thinking the T-Stat too. We didn't have enough time to check it out but it's definitely the first check next weekend.

One of the older guys at the marina suggested the risers, they haven't been changed recently. Of course I'm hoping it's the $20 thermostat and not $400 x2 riser.

Hoses on impeller might be backwards as well.