ZR450 Engine Temp

[titus_4]

Quick back story. Bought the boat (‘11 RZ4 w/ ZR450 motor) fall of ‘19. Ran it with dealer and all worked well. Brought home and put it into storage.

Fast forward to a couple days ago, I pull the boat out and run it on the fake a lake to make sure all is well.

Engine temp climbed quickly to the 170-180 range. I put it in gear and gave a little throttle and it went up over 200. I shut it down thinking maybe I didn’t have a good enough seal on the fake a lake and that they would be lower when I was actually in the water.

Called the Nautique dealer (as they are the PCM dealer near me), and spoke with them. He said I probably smoked by impeller with not enough water flow. I picked up a new one last night and plan on installing it tonight. After leaving the dealership, I started to wonder if this is actually the problem. My 450 is liquid cooled so I questioned how the impeller would affect the engine temperature. I was under the impression that the raw/lake water was only cooling the exhaust.

So my questions are: Would the worn impeller be causing my issue? What is cooling the engine coolant on a closed loop motor? I don’t recall seeing a radiator. Maybe I just haven’t looked around back there enough. I will check my coolant level to make sure it is good but haven’t noticed any leaks and as mentioned, ran fine last fall at dealership and hasn’t been ran since. Boat was stored in heated shop through winter so nothing would’ve froze.

Any help would be great!

[boatwakes]

Hello Titus and welcome to the site. First, I will be gentle but don't ever put your boat in gear out of the water without supplying another water stream to the strut bearing, it'll tear the interior of the strut bearing rubber up faster than you'd think possible and costs about $1200 to replace. Second, if you have freshwater cooling, there will be a heat exchanger at the back of the engine. The heat exchanger is the marine radiator and uses lake water (commonly referred to as raw water) to cool the internal bundles filled with coolant. If you smoked the impeller, it would be immediately obvious because no water would be coming out the exhaust. Is this the case with your engine when it's running? If so, backflush the raw water cooling system and replace the impeller.

The sudden jump in temp could be a number of things including a misreading gauge. The temp alarm is set to go off at 208 so if there is an actual temp problem, the alarm will tell you. I would suggest the following:

- Start the motor with the fake a lake running and check for water coming from the exhaust, you do not need to rev it up
- If there's water, just watch the temp and if it climbs and set off the alarm, you have a definite problem.

Those 6.0 had a notorious overheat issue that an old post addressed from a contributor named Dom W. Forte, something to do with incorrect thermostat spacing from the block. I can't remember what the fix was but I'll see if I can dig up the fix and post it here.

[titus_4]

[QUOTE=boatwakes;n1245901]Hello Titus and welcome to the site. First, I will be gentle but don't ever put your boat in gear out of the water without supplying another water stream to the strut bearing, it'll tear the interior of the strut bearing rubber up faster than you'd think possible and costs about $1200 to replace. Second, if you have freshwater cooling, there will be a heat exchanger at the back of the engine. The heat exchanger is the marine radiator and uses lake water (commonly referred to as raw water) to cool the internal bundles filled with coolant. If you smoked the impeller, it would be immediately obvious because no water would be coming out the exhaust. Is this the case with your engine when it's running? If so, backflush the raw water cooling system and replace the impeller.

The sudden jump in temp could be a number of things including a misreading gauge. The temp alarm is set to go off at 208 so if there is an actual temp problem, the alarm will tell you. I would suggest the following:

- Start the motor with the fake a lake running and check for water coming from the exhaust, you do not need to rev it up
- If there's water, just watch the temp and if it climbs and set off the alarm, you have a definite problem.

Those 6.0 had a notorious overheat issue that an old post addressed from a contributor named Dom W. Forte, something to do with incorrect thermostat spacing from the block. I can't remember what the fix was but I'll see if I can dig up the fix and post it here.

Thank you for the tip about the prop. Never have seen anything about that before.

After I posted this, I spoke with the dealership about the motor and he mentioned the heat exchanger. I completely forgot that it was there.

I replaced the impeller and it looked fine. Went ahead and put a new one in, and I have a spare plus a spare serpentine belt that I will keep on the boat as well.

I did discover that I am low on coolant. I believe that is what my problem is. I didn't think to look at it the other day, because I spaced that it was liquid cooled. It's been way too long since I went over all of this with the dealer where I bought it.

I will add some coolant and monitor the situation from there. Thanks again for the reply!

[titus_4]

Added coolant and went out on the lake. Stayed consistently around 160ish all day. Feel like an idiot for not thinking about that sooner.

[boatwakes]

Dude, only the idiot wouldn't have asked. Questions are encouraged and you learned something about your boat!