R31 Overheating - what should I look at next?

[calcman05]

For the last few years I've had issues with overheating on my D4-300 on my 2015 R31CB luxury edition. When I go above 3000 RPM, generally the temp jumps to 196 and then goes up from there ( I've seen it hit the 200s, but immediately throttle back so I drops back to 185). The temp spike happens on both the Garmin and Volvo monitors.

Not my main concern, but as awareness my WOT is usually 3200. It won't go above.

Video of this -

In the past few years I've had a new turbo put in, as well as had the entire cooling system gone through, including heat exchanger, oil cooler, fuel cooler, trans cooler, after cooler new thermostat, new coolant and impeller. The cooler cores were disassembled and bored as well. The shop also updated my engine with the latest Volvo software last fall. I have also blow air through the seawater intake in reverse to ensure there are no obstructions. All this work was done by a reputable shop.

The boat runs like a dream under 3,000 RPM....it could run all day and never go above 185...so I'm trying to figure out if there is anything to look at next, any thoughts?

- Larger seawater intake?

 

[venajeff]

I don't know the exact specs for your specific engine but in my experience with diesels those numbers sound about right. The WOT of 3200 tells a lot about the amount of load the engine is under, so I am not surprised the engine is heating up. I would be more concerned about putting the engine under that much load. Is the over temp alarm going off? If the WOT is 3200 then your continuous load rpm should be around 2600. The WOT on most marine diesels is only for intermittent use and short durations. Are you getting that much more speed between 2600 to 3000?

 

[calcman05]

I don't know the exact specs for your specific engine but in my experience with diesels those numbers sound about right. The WOT of 3200 tells a lot about the amount of load the engine is under, so I am not surprised the engine is heating up. I would be more concerned about putting the engine under that much load. Is the over temp alarm going off? If the WOT is 3200 then your continues load rpm should be around 2600. The WOT on most marine diesels is only for intermittent use and short durations. Are you getting that much more speed between 2600 to 3000?

This is helpful, thank you. I never get it high enough for a temp alarm to go off since I usually start to throttle back when I see it hit 196.

I typically cruise at 2800 (90% of the time)

There are a few kts gain between 2600 and 3000.

We are a heavily loaded boat between the 3 kids, built in generator, paddle boards, water, and aluminum bottom dinghy. So we are never lightly loaded.

 

[venajeff]

Again, I don't know all the numbers on your boat (I am sure someone on here will), but the only other thing that you might check is your propeller. Perhaps it has gotten damaged. But I suspect it is just the normal operating parameters of the boat. I would only be concerned if I was unable to run the boat at WOT for 10 minutes without the over temperature alarm going off, if you can do that then I wouldn't worry about it.

 

[calcman05]

Again, I don't know all the numbers on your boat (I am sure someone on here will), but the only other thing that you might check is your propeller. Perhaps it has gotten damaged. But I suspect it is just the normal operating parameters of the boat. I would only be concerned if I was unable to run the boat at WOT for 10 minutes without the over temperature alarm going off, if you can do that then I wouldn't worry about it.

I've never taken it to a level where the over temp alarm goes off, I always back down quickly. Right now it jumps to over 200 in under 30 second of WOT, and then I throttle down.

In general is it safe to take your engine to a point of your alarm going off? I've never had another diesel like this before.

Really appreciate your insight so far!

 

[venajeff]

I don't think the ~200 degrees is that crazy, I have had diesels run at around that at normal operating temperature before. But no, the over temp alarm should definitely not be going off at any point. You could probably research and find out at what temperature the alarm triggers. I bet it is closer to 210.
My gut feeling is everything is probably fine with your boat. When I first started reading your post I immediately thought is was probably a clogged heat exchanger or after cooler, or possibly an impeller, but you have addressed all those already (which are all things that need to be done anyways, so that's good).

 

[jacrider]

I have a similar vintage RT31. I also cleaned the coolers, replaced the impeller, etc. I get similar performance ... up to 3,000RPM I can run all day at 185 degrees. Go to 3200 and it will climb higher. I am happy to live with that. We also run a bit heavy ... generator, 2 adults, aluminum RIB, etc.

 

[calcman05]

I have a similar vintage RT31. I also cleaned the coolers, replaced the impeller, etc. I get similar performance ... up to 3,000RPM I can run all day at 185 degrees. Go to 3200 and it will climb higher. I am happy to live with that. We also run a bit heavy ... generator, 2 adults, aluminum RIB, etc.

Thanks for the info, good to know maybe everything is fine, and I should just stop trying to go above 3000!

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[AGLyme]

For reference - my 2013 D-4 climbs to and stays at 185 degs no matter what the RPM.
Haven't used the boat in about 3 weeks - I am concerned about barnacles on the intake screens so I am going to swim under the boat this weekend and clean as a precaution. Not certain if you are in the salt - but could that be a factor?

 

[calcman05]

For reference - my 2013 D-4 climbs to and stays at 185 degs no matter what the RPM.
Haven't used the boat in about 3 weeks - I am concerned about barnacles on the intake screens so I am going to swim under the boat this weekend and clean as a precaution. Not certain if you are in the salt - but could that be a factor?

I have not seen my boat out of the water in a few years, I was not aware of screens on the intake. I thought there was just a seawater strainer in the engine bay. Is there a legit screen? If so, I have never checked it.