R31 overheat

B

bill46

Well-known member
Joined
Jan 13, 2016
Messages
509
Fluid Motion Model
C-302 SC
Hull Identification Number
FMLT3107F314
Vessel Name
Radio Active
My R31CB with Volvo D4 overheats at higher RPM. Was fine a couple of years ago up to 3500 RPM WOT.
Now overheats at 2900 -3000.
We have cleaned hear exchanger, made sure oil and transmission coolers are clear, checked hoses and sea strainer and replaced coolant.
Any Ideas, boat cruises a lot more efficient at 3200 than at 2800.
Thanks Bill
 
Did you check the impeller ?
 
I'm interested in seeing replies to this post. I have a D4260 in my C28 that also overheats at 3000 RPM. I also took all the steps you mentioned and replaced the impeller. My mechanic thinks the through hull is too small. I wonder if replacing the thermostat might fix it?
 
bill46":2jwq75xr said:
My R31CB with Volvo D4 overheats at higher RPM. Was fine a couple of years ago up to 3500 RPM WOT.
Now overheats at 2900 -3000.
We have cleaned hear exchanger, made sure oil and transmission coolers are clear, checked hoses and sea strainer and replaced coolant.
Any Ideas, boat cruises a lot more efficient at 3200 than at 2800.
Thanks Bill
Click to expand...

Bill,

I would start by replacing the raw water impeller on your engine if you haven’t already. Typically that is the symptom of a old impeller, as the blades get old and weak they struggle with flowing enough water to keep the engine cool at higher RPM’s. Let me know if I can help in anyway.

Thank you,
Kevin Lamont
 
Go with the simple solution first. There have been many a vessel that has the raw water for the head coming off the sea strainer that also feeds the raw water pump. This has sucked air in, hence less water flow. Try plugging the hose and see what happens. If your intake was too small I would think the overheat would have been a problem from the get go. If the head disconnect does not work also plug your raw water wash down supply as well if that is also off the strainer. After that check your raw water pump belt and as suggested the impeller.
 
My R31cb has fresh water head, so that may not apply. I vote with the most simple, start with the impeller first.
 
Forgot to mention replaced impeller twice, each year, old looked fine.
Will plug wash down port and have diver scrape paint off intake strainer.
Thanks for ideas.
Has anyone had a bad thermostat?
Had many on GM engines, marine and cars.
 
Not sure where the T-stat is on the Volvo, but the Yanmar is not a fun experience. Historically, the T-stats are not usually the culprit. Capstu, who learned his engine intimately, had an issue with the Impeller shaft slipping at the higher RPM's so stranger things have happened. Check your intake and plug the raw water wash down and take it for a ride. If no joy check that the belt is not slipping and then check the Impeller. Remember check one thing at a time. If you do everything at once you may not be able to pinpoint the culprit.
 
My boat’s Yanmar 4BY2 overheated over a several month and $10,000 problem.

During the hunt I and a mechanic I hired for the stuff I could not reach at 73 years old:

1. Pull and replace the visually undamaged impeller.

2. Monitored heat exchanger with IR gun. Exchanger was not hot so we flushed it.

3. No improvement, mechanic removed and radiator shop flushed it. No improvement, but losing coolant.

4. Bridged out domestic hot water and cabin heater. Leak stopped, but heat exchanger still not reaching expected 160 degree temp for raw water.

5. Opened where print said the thermostat was located. Not there!

6. Mike Rizzo told us where thermostat was on his boat. Mechanic found and removed thermostat from exhaust manifold. Found it on print among exhaust print footnotes. Result, engine ran fine up to 2000 rpm or so. Thermostat not opening when boil tested.

7. The person who sold me the impellers suggested I examine the bottom paint! They had painted the foolish inlet screen partially closed, restricting coolant flow. Pried out screen.

8. Same guy also asked if I had a wash down pump tapped off the raw water pump. My boat did. - it was leaking air into the coolant line. I removed it and plugged line. Now the engine ran up ti about 2800 rpm before overheating. In the process I found 2 more broken hose clamps.

9. I mentioned the painted screed to the impeller sales person who suggested I remove the nearly new impeller and test for slippage. I did, it did slip, so I put in the third impeller. The engine now runs wot for hours without overheating.

Thanks to everyone who contributed ideas. While the mechanical work was very expensive, everything Eagle Marine did was discussed and approved in advance.

Lessons.

1. Some of the problems were Yanmar unique such as the thermostat location.

2 the defective hose clamps and poor decision to draw wash down water from the raw water inlet are probably problems on any Ranger or Cutwater and may be problem on your boat.

3. The Thur Hull screen just won’t work if painted and may be to small in any case if you run wot for long.

4. Impeller slipping is apparently more common than I knew and should be suspect if tour sea strainer or screen clogs.




Stuart Bell
Ranger 25: Shearwater
(561) 352-1796
 
Bill,

On our 2014 R31CB, the raw water wash down has its own strainer separate from the engine.

In the hottest summer days when operating the engine and generator, I've had to prop open the stern seat slightly to get more air flow into the engine compartment, as the generator would shut down from getting too hot. I'm not sure if this would have any effect on the Volvo in your case. Just thought I'd mention it.

Al Sr.
 
bill46":1anj6a6u said:
My R31CB with Volvo D4 overheats at higher RPM. Was fine a couple of years ago up to 3500 RPM WOT.
Now overheats at 2900 -3000.
We have cleaned hear exchanger, made sure oil and transmission coolers are clear, checked hoses and sea strainer and replaced coolant.
Any Ideas, boat cruises a lot more efficient at 3200 than at 2800.
Thanks Bill
Click to expand...

Bill, could you quantify the actual temperature range when you state, "...overheats at higher RPM."?

On my 2014 R31S, the Volvo temp gauge shows 185 for all RPMs, until I exceed about 3200 RPM, then the temp gauge jumps to 195-197 and stays there indefinitely. Does your overtemp condition greatly exceed 197? Does it fall back to 185 when you go below 2900-3000 RPM? This information might help to guess about what is happening.
 
Tested today with raw water wash plugged. Maybe 100 more rpm before heat. No air in strainer. Exhaust water injector and hose 100 degrees with 85 deg. water in. Next plan is thermostat, maybe not opening completely.
201 deg at 3100. 185 to 2900. Wot 3370. Hot in 2-3 min.
Entire raw water path has been cleaned inspected.
Believe exit water would be hotter if flow restricted.
Will keep posted.
Thanks for advice.
 
I had a similar temp reading when my engine’s thermostat was jammed shut. Take it out until temp tests low, then put in anew one.

No problem with no tstat for a test run.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796
 
thanks - will try no stat first
 
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