Yanmar 6BY2-260 operating temperature

[HamsterMike]

I am a new owner of a 2010 Ranger 29 with the Yanmar 6BY2-260 engine. 630 hours. At 1500-2000 RPM the temperature gauge reads 190 - 200 degrees F. If I increase engine speed to 3000 RPM it will read 210 or higher, at which point I slow down and let the temperature go back down. My mechanic says Yanmar BY series engines run between 210-215. Does this sound right? My gut tells me that anything over 212 is not good.

 

[Diatom]

My 4BY2-180 runs at 3600RPM: 194-195°F, even WOT won't push it over 197°F.
/tmm

 

[kelpline]

One mistake I made the first season with our Yanmar 6BY2-260 was not filling the engine coolant right to the bottom of the cap. I thought the plastic expansion tank filled to the middle line showed the coolant as full, not so. Once we filled to the bottom of the cap, the temperature moderated to 195. Also we added side fins to the Bennett trim tabs, and larger fins, a suggestion received from Brian of BB Marine. This brought the bow down, lifting the stern.

 

[aroett]

Hello,
Congrats on the new boat!

Seems like I have the same boat (2010 R29 with 6BY2-260, in Vancouver BC). I purchased last year so still in the learning phase. I too have had this question so search this forum for some responses I got.

My engine also seems to run warm and follows a similar trend as you described: 200-207deg to 2500rpm, then goes up to 208-212 at 3000-3500rpm. Various mechanics have suggested many things - not large enough water intake, thermostat problem, temp sensor problem, and prop over-pitched. Thermostat changed before I bought boat. Temp double checked with heat gun and seems real. Another issue I have is that I can only get to 3800rpm and engine gauge reads 100% load. My mechanic thinks this points to engine being over-propped and would change that 1st before any other troubleshooting. I did take 1" off prop pitch when purchased - didn't make a difference. Will probably reduce a further 1" pitch next year.

Have used the boat 100-hours so far and no issue - love it! I usually run around 2000-2800 rpm and temp sits around 203-208. If I do speed up, temp increases to 210-212, but comes right back down when I slow down. I too would like to get to the bottom of this and be interested in any findings or input from others.

Are you able to get full power - 4000rpm?
Does anyone know what is the stock prop size/pitch for this boat?

Cheers,
Adey

 

[knotflying]

The BY's do tend to run hot. My 180 at WOT ran at 206. I suspect your engine would run hotter. Was your heat exchanger ever serviced? Short of removing it, you could run a continuous circuit and flush using Ridlyme. You would have to remove the impeller and then reassemble the pump. Then create a a closed loop. I used my raw water pump to pick up the Ridlyme from a bucket to the strainer (valve closed from pickup) then disconnected the large hose to the elbow and a fitting with a smaller hose back to the bucket. Circulate the Ridlyme and then let it sit and then circulating again and doing this several times over a couple of hours, This should remove any scale buildup. In the interim, remove the exhaust elbow, inspect it and place it in the bucket so any scale gets removed. The small water hose on the side of the exhaust elbow needs to be removed and plugged with a dowel to prevent water from coming into the bilge. After you are done wire brush and rinse the elbow and reconnect everything. PS. You will most likely have to get some hoses and fittings to make all the appropriate connections and switch the intake and outlet on the raw water pump. This is not a difficult project. just a bit time consuming. Quite frankly one of the easier jobs to do. Also, make sure your pickup is unobstructed by barnacles or growth.

 

[fishheadbarandgrill]

I cruise at 2000 rpms at a temp of 192F. I read on a marine diesel forum that the BY260 thermostat opens at 190 and is fully open at 206F.

 

[BB marine]

As Bob has stated the thermostat specs are 190F open and full open is 205F. If the strainer is not fouled, exchangers clean and not fouled, The raw water pump and impeller are in good operating condition. The engine should be able to operate @ WOT and the thermostat should be maintaining the engine temperature within its specifications. The engine should not operate above the thermostat range. Yanmar designed this engine to have an operating temperature of 190F to 205F and should stabilize in the middle of this range. The unfortunate problem with most Ranger Tugs and engine cooling is the engine through hull intake is too small. This does not allow adequate raw water flow to cool the exchanger and the thermostat must operate at full open position with the coolant temperature continuing to climb. The engine is designed to operate within the thermostats range maintaining a temperature and not allow it to run away. If an engine does not operate within its design there is an issue. Most Ranger Tug owners through out the years have accepted, in a Ranger Tug, it is normal for theses engines to run hot when at high load. It is not! You should be able to cruise at any RPM and see little fluctuation in operating temperature. Seeing 10 to 15 degrees fluctuation in a modern day engine is not normal operating procedure. Most Tug owners operate at lower loads and don't worry about the high operating temps of higher loads. I will say that the D4 and D6 Volvo installations are better they have larger through hull intakes. The engines run closer to 185F at high loads.

 

[knotflying]

I also found that there have been instances that the raw water for the toilet is off the strainer. This has caused diminished water flow to the engine. A check valve on the water line to the toilet has reduced this problem.