The engine on my H44 runs hotter than I would expect. At 2500 rpm it reaches about 88 C after running for extended periods; at 2600 rpm it approaches 90C; at 2200 rpm the temp drops to about 80C. The max rpm for this engine is about 3000 rpm. I have a feathering Maxprop. My hull and prop are clean. Right now the water in Raritan Bay where we sail is about 21C. I have had the engine checked by two different Yanmar certified mechanics who could find nothing wrong. The raw water system checks out fine - the intake strainer is clean and the raw water pump is in good shape - plenty of water flushes through the system. With a mechanic, I opened up the raw water side of the heat exchanger, and it was free of obstructions. The engine has only 350 hours, and both mechanics were sure that the fresh water side was ok. I replaced the temperature sender thermistor and still got high temp readings. I have also replaced the thermostat. One of the mechanics checked the fresh water pump temperature using a pyrometer, and it seemed to register slightly lower temperatures, but I am suspicious of these measurements since they depend on the infrared emissivity of the painted pump surface. What engine temperatures do other owners read when running at 2500 rmp for extended periods - long enough to heat up the 11 gallon house water tank? Thanks, Larry
- Status
When was the last time you chaged your antifreeze
And what color is it? Red or yellow. Apparently the red goes bad after one year. I had a similar problem and was told to flush the old a/f and refill fresh antifreeze. The manual recommends that this be done yearly. Problem solved after flushing the engine w/cleaner and refilling. Make sure that force the antifreeze from the hot water heater before you add the cleaner. 46
And what color is it? Red or yellow. Apparently the red goes bad after one year. I had a similar problem and was told to flush the old a/f and refill fresh antifreeze. The manual recommends that this be done yearly. Problem solved after flushing the engine w/cleaner and refilling. Make sure that force the antifreeze from the hot water heater before you add the cleaner. 46
Over Propped?
That maximum RPM does not sound right. Shouldn't that engine reach 3600 RPM at WOT? My 40.5 with an earlier Yanmar is supposed to. If yours does not reach the max one-hour rating RPM, and in fact will only reach 3000, then that is likely the problem and you need to lessen the prop pitch. I changed props also and only get 3200 RPM and it runs hotter beginning at 2900. The prop representative advised me the prop was overpitched and to have it adjusted next haul. Rick D.
That maximum RPM does not sound right. Shouldn't that engine reach 3600 RPM at WOT? My 40.5 with an earlier Yanmar is supposed to. If yours does not reach the max one-hour rating RPM, and in fact will only reach 3000, then that is likely the problem and you need to lessen the prop pitch. I changed props also and only get 3200 RPM and it runs hotter beginning at 2900. The prop representative advised me the prop was overpitched and to have it adjusted next haul. Rick D.
Yanmar 4JH4E temp
Larry, The max rated rpm for the 4JH4E is 3,000. Max continuous is 2,907. My temp guage stabalizes at approximately 78* C. I have a Max prop as well and the pitch is set to 22*. At 22* of pitch the boat performs as follows: 2800 rpm = 8.2 kts 2600 rpm = 7.8 kts 2400 rpm = 7.5 kts 2200 rpm = 7.0 kts all readings SOG in flat water. e-mail direct at twolanzyk@comcast.net if you have further questions.
Larry, The max rated rpm for the 4JH4E is 3,000. Max continuous is 2,907. My temp guage stabalizes at approximately 78* C. I have a Max prop as well and the pitch is set to 22*. At 22* of pitch the boat performs as follows: 2800 rpm = 8.2 kts 2600 rpm = 7.8 kts 2400 rpm = 7.5 kts 2200 rpm = 7.0 kts all readings SOG in flat water. e-mail direct at twolanzyk@comcast.net if you have further questions.
Sounds like a busted thermostat
I've seen thermostats get lazy over the years. Instead of being open or closed over a 5-7 degree range they just open and close as they feel the need. Saw one that had a 25 degree delta. You can check by putting it in a pot and boiling it. Use a meat thermometer to measure the water temp. It should open quite quickly as the water temp goes through the rated temp. the rated temp is usually stamped on the thermostat. Could also be plugged/restricted anty passages in the engine. You have to drain most of the anty to check the thermostat anyway so.......
I've seen thermostats get lazy over the years. Instead of being open or closed over a 5-7 degree range they just open and close as they feel the need. Saw one that had a 25 degree delta. You can check by putting it in a pot and boiling it. Use a meat thermometer to measure the water temp. It should open quite quickly as the water temp goes through the rated temp. the rated temp is usually stamped on the thermostat. Could also be plugged/restricted anty passages in the engine. You have to drain most of the anty to check the thermostat anyway so.......
Guage Calibration
Larry, Those gauges are about $15.00 gauges. I wouldn't expect it to be extremely accurate. Bill
Larry, Those gauges are about $15.00 gauges. I wouldn't expect it to be extremely accurate. Bill
Problem solved
The high temp problem appears to be resolved; thanks to all for your input. The key clue was the posting from Tom Wolanzyk who has the same engine and prop as I do. He explained that that gauge reading on his boat is independent of RPM . I called Mastry Engine who supplies Yanmars to Hunter. Given this information, and all the things I already tried, Mastry suggested using a engine coolant flush on the fresh water system. I did this today using Prestone Super Flush. This is a tedious task, since it requires waiting for the engine to cool down twice. The flushed liquid came out rust colored. Amazingly, the treatment has seemed to work! Now with premixed Yanmar 50-50 antifreeze back in the engine, the temp stabilizes at about 80C even at 2600 RPM. It's possible that the antifreeze was bad, but my guess is that there was scaling on the fresh water side of the heat exchanger. Costs to get to get to this point: $450 for mechanics that didn't solve the problem but at least eliminated possible causes + about $200 in parts (gaskets, thermostats, sender, etc). The good news is that I learned a lot about my engine's cooling system and can now probably tackle repairs on my own. There is still the open question of why the scale built up in the first place.
The high temp problem appears to be resolved; thanks to all for your input. The key clue was the posting from Tom Wolanzyk who has the same engine and prop as I do. He explained that that gauge reading on his boat is independent of RPM . I called Mastry Engine who supplies Yanmars to Hunter. Given this information, and all the things I already tried, Mastry suggested using a engine coolant flush on the fresh water system. I did this today using Prestone Super Flush. This is a tedious task, since it requires waiting for the engine to cool down twice. The flushed liquid came out rust colored. Amazingly, the treatment has seemed to work! Now with premixed Yanmar 50-50 antifreeze back in the engine, the temp stabilizes at about 80C even at 2600 RPM. It's possible that the antifreeze was bad, but my guess is that there was scaling on the fresh water side of the heat exchanger. Costs to get to get to this point: $450 for mechanics that didn't solve the problem but at least eliminated possible causes + about $200 in parts (gaskets, thermostats, sender, etc). The good news is that I learned a lot about my engine's cooling system and can now probably tackle repairs on my own. There is still the open question of why the scale built up in the first place.
- Status