PCM/crusader 409 overheat raw water cooled
 

Welp, broke something. Axis t22

Boats overheating, cleaned strainers in oil coolers and sea strainer, replaced impeller which was beat but not shredded, pulled and tested thermostat in boiling water which opened (that thermostat housing design SUCKS by the way).

Boat climbs to 210 and holds when idling. As soon as you give it throttle it will climb and alarm. Happened suddenly when wake boarding the other night, no warning, just 20 minutes of riding and bam.


I’m thinking either something is up with thermostats, but it opened in boiling water.
Next step is to check circulator pump and to verify it is not air locked and fill the system with freshwater from there. If that doesn’t work we will replace thermostat, anything beyond and we are back to the dealer for warranty repair...


Any other tests I can do at the dock? I really don’t want to lose weeks of summer at the dealer if it’s something I can fix myself.

Anyone have these problems before?

Did you lose any fins from the impeller? If so they might be lodged up stream somewhere. Are you sure the intake from the scupper is not clogged?

Nope no clogs, Fins would be caught in the oil coolers. I did pull some pine needles out of one but the problem persists.

Boat sits on a lift and I checked the scupper is clean. Blew it out from the sea strainer as well.

I’ve been going down the line from raw water intake up, we have water up to the thermostat yesterday but that’s as far as I got because the thermostat took 2.5 hours yesterday. That is such a bone headed design for a maintenance item, I swear if I could punch some pcm or gm engineer in the face for that.... icing on the cake is that it is zip tied to the block

I have the same ZR409 engine in my boat. Have you double checked the impeller? Some of them will spin the hub....so the impeller will spin some (probably just enough at idle), but if you put power to it then the hub would spin but impeller will not. That engine has a 160 thermostat and should run between 163-170....if it goes over 180 there is an issue. I agree, I don't like the thermostat setup either and you gotta make sure that casing is installed the correct direction when you put it back.

There is a screen in the trans cooler, sounds like you checked that....have you also checked under the boat where water comes in to be sure nothing is clogging things down there? There could be debris caught on the scupper or maybe even the intake valve. I would back-flush everything (especially cooler) just to be sure there is no debris or clogging going on (Here is how: when back flushing a cooler unhook the leading Hose To The Cooler and undo the back Hose of the cooler and hook up a garden hose . Then Flush It out) but i highly suspect the impeller, its rare to have thermostat issue tho of course that is possible.

When you pull impeller housing apart to double check it, be sure there are no grooves on the cover since that can break the seal (if grooves are really deep it can cause your exact issue), grease the o-ring as if it is sucking any air and not getting a tight seal that can also cause issues. I use dawn dish soap on impeller, makes it easy to get in/out.

Minor update- 2 different thermostats: overheats with both.

Pull thermostat: runs cool.

Both thermostats open in boiling water....

Does the circulation pump sound normal? Just wondering if the impeller for that has slipped its hub. Sometimes those metal impellers will crack and then not actually spin and the water cannot circulate the engine. With the thermostat out, the raw water pump may be doing it’s job for it......

Pull the belt of the circulation pump and spin it by hand and see if it feels like you’re actually pumping/moving water.

This is EXACTLY what I was thinking. No back pressure from the reduced aperature of the thermostat so it is able to cool the motor just off the raw water pump. That and the way it failed...

I didn’t hear anything alarming but there was a new sound coming from the belt area today when I had it all apart. Intermittent whirring sound. I pulled the hose clamp off to look in but didn’t see or feel the fins.

How big of a job is that pump?

I’ve been through the whole system now. Pointing towards clog, circulator, or thermostat. Most likely the circulator


Ps got the thermostat housing down to a science, can change that thermostat in 15 min if you don’t drop the nuts.

Circulation pumps is not that big of a job. I would pull it and check

Did you check the screen in your exhaust thermostat housing? PCM lead us to that and sure enough it was clogged.

Forgot to mention this is a 13 centurion Enzo with PCM 409 closed cooling system and engine temp was fine I had a exhaust temp overheat last weekend.

Naw I don't think we have that because we are raw cooled...I'll updated when we find out the issue.

It is my understanding that all of these 409's are dual systems. Yes, they are raw water cooled but also have Dexcool coolant running through parts of it as well. Only time I've ever had an alarm on mine it was the thermostat but clearly you've already replaced that

Simplej, what year is your boat?
If it’s a 2013-14 im willing to bet you have the same issue I did and if it is PCM told my service shop to eliminate the screen that the exhaust thermostat sits in.

Its actually technically the crusader- there is no coolant in the system. I looked for that thermostat. Where is it located? Its a 16

Ahh well I’m no help to you then sorry if I sent you on a goose chase.