Blown impeller hoses

Last weekend, I blew the output hose from the impeller. I replaced it, then the next day, the next hose downline blew!! Didn't just pop off - it ripped lengthwise.

There's the 1.25" hose that is on the output of the impeller, then the "T" for the shower, then another 1.25" hose that goes up to toward the thermostat and on into the water pump. I find it extremely unusual that both of the output hoses downline from the impeller would blow in 2 days. They split laterally (lengthways).

I have an '03 B52 with the PCM (Chev) Excalibur 330. It runs about 175 degrees normally cruising or pulling a tube. I noticed it was running about 180 at the time of failure(s). But that's not very hot. I have seen a lot hotter temps surfing/boarding. I was thinking there may be a blockage causing too much pressure. Perhaps the thermostat?

I've replaced both hoses and ran it about an hour - with no further blowouts. However, both blowouts happened after running about an hour the first time. Could it be just a coincidence? I had two friends with 02 B52's with me that day and an 06 B52 - and none of them have ever had this happen. It's got 330 hours on it. Seems to me that an impeller shouldn't be capable of blowing out a hose - unless the hose was just old and weak.

Anyone seen this happen before?

I thought most boats had a 140 or 160 degree thermostats? Maybe yours has a 180 but really if everything is clear and the tstat is working it shouldn't really go above that temp at all. In general though I don't think 180 degrees is that hot for an engine. I believe cars run at least that high of a temp.

I hadn't heard about the problem on PCM's but Indmar in 07 used some bad "J" hoses that would blow lengthwise like you are talking about.

I had the same problem with my 02 Super Air one time. Started blowing out the J-hose and my temps were doing the same thing as yours. Finally figured out a piece of a shredded impellor got sucked up into the engine making its way to the thermostat and got lodged in there. This caused the back pressure which was blowing out the hose and since not as much water was flowing through the engine the temps rose. I took mine to the dealer.. they popped off the thermostat.. pulled the piece of impellor and viola, problem solved.

John

How many hours on the old hoses? I lost hoses at the impeller at about 325 hours and within 10 hours of each other. There is a lot more vibration on these hoses than the others because the pump housing mount causes more flex than other hose locations.

I put on a couple hundred more hours and purchased spares for the preformed hoses and I have a couple lengths of the non-preformed. I also carry a couple different sized repair kits.

Over 28 years of ski boats, I cannot count the number of hoses blown. Typically they break at the fitting and you can cut the bad end and reattach the hose....then replace the hose back at the dock.

Another point, I also found it you are running hard, a small hole at the fitting will start to split lengthwise on the pressure side only. I learned this after using tape as a repair and limping home when my nervous of sinking amongst the alligators wife kept pushing the throttle thinking she would get us back quicker and safer. Every time too much throttle was applied the hole would open more. I stopped the boat, cut the hose and ran for two more days before replacing on the "fresh end".

If you catch the problem before loading it up with pressure from the pump you can stop the tear by cutting the bad end and reattaching.

Turned out that a broken impeller piece was plugging the thermostat bypass hole. I removed the thermostat and cleaned the area and replaced hoses. Ran cool and perfect after that!

Glad you found it. Makes sense.

180 is HOT, 175 is HOT, something else is wrong besides bad hoses. Should never be running much over 160.

I'll bet your trans cooler is full of more burned impeller blades.

175-180 is not too hot for a modern efi motor.....carb motors typically run 160-165, efi motors quite often run thermostats closer to 180.

glad you figured it out.

To further Meathead's post - 180 is not HOT. I have 496 8.1, 180 is normal operating temp on mine and other small block EFI engines.

I run a 2011 383 Mercruiser stroker EFI and it does not run that hot. And mine is usually WFO.

Since it was fixed (impeller pieces pulled out/new thermostat) - it stayed about 160*