Impeller issues
 

Hello all. Yesterday I took my boat (2012 MB Sports B-52 23V) out of storage, installed the batteries and returned to service. I replaced the impeller with a new kit and then brought to the lake. I started it up at the launch and all seemed fine, so after about 5 minutes we left the launch. About 5 minutes later then alarm sounded and the motor went into limp mode. The temp was approaching 200 and I figured the impeller must not be drawing water. I let it rest a while and then idled to the marina. I removed the impeller and it was dry, but couldn't find any reasons why it was dry. I inspected everything, reinstalled, and then ran again but still no water going through impeller. I have a PCM EX 343, and the raw water inlet runs through the transmission, then to the motor. Is it possible that it is cavitated since the block was empty from winterization? I know it is usually empty after winterization so I can't imagine that is the issue. Any thoughts are appreciated.

Check to see if the ball valve at your thru hull that is closed. Otherwise check the hose to make sure it's all clear from any obstructions. Otherwise it could possibly be the raw water pump is gone. It's a process of elimination. http://www.pcmengines.com/assets/Upl...wners-2011.pdf

Do you have a faucet that located direct behind the inlet on the boat bottom?

I do not have a shutoff on the raw water inlet. I know all new boats are supposed to have one but mine does not. Thanks. J

And one more - some mechanics doing winterizing with install the tape on the water inlet to outside to prevent insects into during storage. I saw this. And check water strainer, if you have the one.

Assuming there are no obstructions, it could be that since the pump/impeller is dry it will not pull water without first being primed. I've had this issue on my boat a few times. The raw water hose routing on mine is such that I can remove the inlet hose from the transmission heat ex-changer and pour water down it. The hose leaving the heat ex-changer goes directly to the raw water pump so I'm filling that hose and the pump with water so it can prime and pull water. That has worked every time.

If you ran that long with the raw water pump dry you will need to replace the impeller as I'm sure it is toast now and will never mover water like needed. Also check your raw water strainer for cracks or if the o-ring is missing/cracked/seated incorrectly. It only takes a small air leak upstream from the raw water pump for it to not move water well.

Check to be sure you don't have the hoses reversed

To eliminate bad pump, take the water pump housing cover off and bump the starter without turning on the engine to verify the impeller is still rotating. Best to have an observer but if you're a one man crew usually when you turn the motor over the impeller works itself out a little as evidence of rotation.

sometimes you have to prime the impeller. counter-intuitive but I've seen the same situation with a new impeller and you actually gun it and the water rushes in to prime and then you're good.

The same thing just happened to me... Changed the impeller and then no cooling. My problem was that I oriented the pump on the bracket 180 degrees off so the inlet hose was hooked up to the outlet end of the pump and the outlet to the inlet. Simple fix if you call having no access simple.

It is a really good idea to take a picture of your pump inlet orientation and the impeller orientation inside the housing before removal. Saves a ton of worrying and second guessing.

If it was blowing bubbles, you have the lines reversed. I've done that before. Otherwise, I bet it needs priming.

^^what Brent44 said^^

I've seen it several times and did it my self once.. I always mark the housing and one bolt hole when I remove the pump....

Do you have a heater? I never had a problem and then put in a heater last year and this year took me a while and ruining a impeller to figure out that you have to close off heater hoses (just by pinching) first time running the boat. Anything change since last year?

Probably not the case since it's a new impeller but I've seen where the rubber veins will detach from the spline hub on the impeller and the brass hub spins but veins do not! Just something else to check if you've ruled everything else out.