R31 Overheating - what should I look at next?

C

calcman05

Active member
Joined
Feb 3, 2024
Messages
44
Fluid Motion Model
R-31 CB
Vessel Name
DINGLEHOPPER
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?
 
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?
 
Last edited:
venajeff said:
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?
Click to expand...
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.
 
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.
 
venajeff said:
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.
Click to expand...
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!
 
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).
 
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.
 
jacrider said:
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.
Click to expand...
Thanks for the info, good to know maybe everything is fine, and I should just stop trying to go above 3000!

I am very interested in the Veem partnership with Sharrow prop for their inboard motor props. I talked to sharrow last month and they said they are actively testing the new props with in oard setups and will have some more real world performance info in the next 6 months, as well as more pricing insight. I'm secretly hoping they get some good real world efficiency gains, and I could cough up the money for a new prop that might put less strain on the engine or simply gives us a few kts more at the same RPM. Time will tell!


sharrowbyveem.com

Sharrow by VEEM

A new standard for innovation & excellence in marine propulsion
sharrowbyveem.com sharrowbyveem.com
 
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?
 
AGLyme said:
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?
Click to expand...
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.
 
Last year we had a terrible barnacle year here in Connecticut. EVERYTHING was covered with barnacles. Pulled the boat mid-season to clean and re-launch - my top end speed was down by 4 mph.
This year I had the yard paint the prop, stabilizers and rudder with a very expensive coating (Propspeed - $1,500) and it really works... However, after the Propspeed was applied and the bottom was painted - I noted that the intake screens/covers (one for the Volvo and the other for the Genny) had barnacles inside the covers - so I took an ice pick tool and cleaned them out. The screens/covers are small, less than the size of a lemon. Mine were covered with good old bottom paint - but it didn't do the trick on the metal surface which is why I want to swim this weekend and clean if necessary.
The location of the Volvo screen/cover is where the raw water intake is. Ditto the Generator intake.
 
When I bought my 2013 R-29 Classic last year, we had a very similar experience to yours. Our marine surveyor noted it was overheating at high RPMs, which we priced into the purchase. We took it to our Volvo/Penta repair shop and had them service the heat exchanger, which is recommended every 7 years. Given ownership turnover of our vessel, I reasoned it may have never been serviced. Our shop did a very thorough job and the overheating problem was solved. Runs like a top now--no overheating.
 
venajeff said:
The WOT of 3200 tells a lot about the amount of load the engine is under
Click to expand...

I think this is hitting the issue on the head. An R31 (or rather a D4-300) should have an WOT of 3500-3600, if it's getting stuck at 3200 then it's being severely loaded and not running right, likely leading to your issues.

On my R31 I can run at 3500rpm for more than 30 minutes and my temps stay locked at 185. And at 2900-3000rpm I'm burning at most 10 gallons an hour. Normally my cruise is 3100-3200 at 11-12 gallons. WOT is 15 gallons. The only time my temps have gone higher is when I sucked in kelp and clogged my strainer.

Look at fuel filters, bottom cleaning, unnecessary weight on the stern (these boats squat, do you have drop fins installed?), prop adjustments, fouled heat exchanger, etc.
 
Last edited:
Don’t overlook clearing the seawater trap.
 
calcman05 said:
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? The engine should maintain a consistent temp based on the temp. of your thermostat. I see no mention of your fuel flow at your mentioned 3200rpm. Consult the Volvo fuel curves for your specific engine. If it is passing more fuel than the fuel curves indicate it should for that specific rpm you are trying to work the engine too hard.
Click to expand...
 
I've done a lot of investigation into this over the past couple of years. Our 2019 R-29 CB would stay at 185 after it warmed up and would only go over 185 at or close to WOT if the bottom was fouled. As soon as I got our 2021 R-31 CB, I noticed that I would go up into the 190s fairly quickly when over 85% of engine load. At first I thought there was a problem, but the bottom was clean and everything else checked out. Over time, I've noticed that it will sit generally at 187 degrees at approximately 3250 RPM and seems to be happy there. If I bring the revs higher the temp goes up into the 190s, but doesn't overheat.

Looking around the web, I've found that this is normal. I also read some posts stating that for a while, Volvo had programmed the electronics to display 185, as long as the temp was within a certain range. I don't know it that is true or not, but I have a replacement ECU and I seem to get the full range of temperatures.
 
I successfully flushed my VP D4 300 engine with West Marine concentrated descaling fluid. I disconnected the raw water hoses at the water pump and at the mixing elbow. I also removed the small hose at the cutlass bearing and plugged that hose so the descaling fluid would not leak from there. I bought two plastic PVC fittings from Home Depot and found two garden hose fittings at Ace Hardware to screw into the PVC fittings that allowed me to clamp everything to two small garden hoses which l led outside to a five-gallon bucket where I used a pond pump to circulate the descaling fluid through the raw water engine components. I pushed the water backwards, i.e. in at the mixing elbow, out at the water pump so any sea grasses or other "stuff" would hopefully be pushed out of the system more easily. The pond pump I bought off Amazon a while back - it is the same pump I use to push canal water up to the boat to run the air conditioners when I have the boat on my boat lift. The descaling concentrate is a 5 to 1 mix ratio which means I used one gallon of descaling fluid and about 4 gallons of fresh water to fully prime the pump and fill the five-gallon bucket. I ran the descaling fluid through the engine for about 8 hours, and my overheating issues went away.
Flush Discharge at Water Pump.jpeg

Flush Input at Mixing Elbow.jpeg
 
I could not upload a small video of the pond pump in action - here is a screen shot of the flush setup in the five-gallon bucket...
1787864081713.png
 
You must log in or register to reply here.

  • Tugnuts.com is the community hub for Ranger Tug, Cutwater, and Solara owners. Since its inception in 2008, the Tugnuts forum has grown into an active and thriving community of more than 9,000 members. It serves as both a meeting place for the best boating community online, and an invaluable archive of information.

  • User menu
Back
Top