I have a cobalt 01 with 420 HP Volvo 8.1 GSI that has a exhaust crossover/equalizer hose that runs between the two manifolds. For some reason, every once in a while when I do a full speed run, the hose blows, it blows out at one side (usually the port side), then I have to limp back home as I lose ability to go past 3K depending on the size of the hole.

Gone thru 4 hoses already last year, and one this year.

Any ideas? The boat runs great otherwise.

WOW has a dealer looked at this for you yet? Are you blowing a hole in the hose or is it poping off.

It's blowing a hole. The dealer was clueless. It happens every so often. Kind of hard to predict when it will. Always during full throttle runs however. It's a mystery.
If anyone has any ideas I'd appreciate it.

The crossover is a rubber hose?? Sounds like heat relaated...When you replace it is the inside blistered?

replace it with a Trident hose and you should be fine.

The dealer should have called volvo teck support for you at the time [imo]
You could try calling volvo customer support to see if they have a real fix for this. It should not be doing this as long as you are buying the hose from volvo. Also volvo does have a parts warranty for one year so you don't half to keep buying one. just a idea.

Update

Just got the boat back from the Volvo Dealer after dropping some $$ at the dealer. They said there was a tech bulletin from Volvo that called for replacing the rubber exhaust mating hose from the risers to a different one that allows additional clamp in the middle. This was done for both risers, also while at it, they resealed the risers to the manifolds which were confirmed to be in good shape. They measured with an IR gun temperature at the crossover hose. Went from 110 degrees to less than 80 degrees after the updated riser hoses with additional clamps. The manager was confident this would take care of the problem. The impeller was checked and found to be ok. Exhaust path was checked to make sure there were no blockages.

Now, I'm just waiting for decent weather to take it out on the lake for some full throttle testing to make sure all is right and make sure the crossover hose does not blow again.
=). I'm hoping this took care of it!

Last year, I already upgraded that hose to a super duper expensive trident silicone hose ($$$) that was designed for super high temps, that still blew.
We shall see if the updates to the exhaust hoses I just had done took care of the problem.

Now that you reminded me of that bulletin I would be willing to bet it will fix it, I say that becouse I ran your story by another good boat teck guy I know and his guess was about the same as what you just had done, On Mercs 8.1 engines they only want you to run thru transom exhaust only do to back pressure problems they had in the begining and volvo still goes thru the Y pipe and out the prop, And volvo came up with that idea becouse they don't like open thru transom exhaust on boats, To easy to get water back in the engine for them.

I know this is a very old thread but I've just had the same issue on my VP 8.1 after service where exhaust Y Pipe, manifolds and Risers were all replaced. The exhaust crossover hose blew a hole in it on the port side (6mths old) probably during a 75% open throttle run. Anyone else experienced this?
What is the VP Tech Bulletin referred to above? I can't find one about the exhaust crossover hose.