Yanmar UTE question ...
Well, I could sure use some advise. My engine is a Yanmar 4JH2-UTE. I have a 2.63:1 gear reduction swinging a 4 blade 20x18 wheel( pretty sure on prop ). This is on a semi displacement New England style pick nick type boat, 25 feet long, dry weight 6400 pounds, loaded around 8000 with passengers, gear and fuel.
A month ago or so I had a survey and the tach reached 3600, and 12 knots at 2900 rpm. That is on spec, however, low fuel, no water, minimal gear and two adults.
When I picked it up, it over heated,Florid water and weather much warmer after survey. We flushed the raw water side and found the thermostat missing. We replaced with a 173 degree thermostat from Yanmar. Boating in the cooler Mississippi River, the motor sits at about 85 degree C all day.
However, it used to grey black smoke at about 2600 rpm or higher, the more RPM the more smoke. At the dock, after running the river, idling down, I would raise RPM a few times and soot would float out exhaust. Now after about 45 hours of running up and down River 2600 to 3000, and using diesel kleen there is almost no smoke, gotta really look hard to see it and only after 3100 PRMs.
However, My load is my wife and I plus two 60 pound plus dogs, 2 coolers, gear for 4 days trips plus 60 gallons of fuel and 10 to 20 gallons of water. When traveling up or down current, I can only manage 3450RPMS.
I Have wondered if may be I have a sticky injector, or may be over propped a bit ... or something else? Down river, with load above at 2900 RPM I do about 10.5 knots, up river it is like 7.5 knots ...not 12 like during the survey. Is this likely do to the load or maybe is something wrong from the overheating?
I look forward to any and all replies as I really love the boat and do not want to hurt the engine.