Author Topic: The iron sail on a 303  (Read 378 times)

MangoCats

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The iron sail on a 303
« on: February 18, 2019, 09:21:24 AM »
I'm new to my 303, and up until yesterday had only motored around under 2100RPM (separate story, to confirm the accuracy of my console tach I used an optical tach on the flywheel, 2100RPM as read by a cheapo optical tach on the flywheel corresponds to 1900RPM on the console needle, I trust the new cheapo optical over the 35 year old console...)  The GPS will generally read around 5 knots at 2100RPM on a calm day - we motor in a river so that's usually 4.5 against the current, 5.5 with it.

Yesterday I finally throttled up to ~2600RPM and yes indeed it does move faster, but the motion of the hull is much less settled.  We were running downstream, 5.5 GPS knots at 2100, and by 2600 the GPS was reading ~6.7, which should be about hull speed for a 25' waterline, though maybe still 1/2 knot short accounting for the current.

The main "unsettling" behaviors were a tendency for the heading to wander, at 5 knots through the water it stays on course very solidly, at 6+ it required constant input at the wheel to hold a course - maybe my nice comfy 11' beam is coming into play here?  Also, the back of the boat squatted down about 4", where the exhaust is just above water at 5 knots, it's fully below at 6.  There was also a notable increase in exhaust odor, not foul, but notable.

I'm happy to cruise at 2100RPM / 5 knots, but have read here and there about Yanmar (and other diesels) "liking to run" at 75-80% of rated RPM (3400 for my 2GMF) to prevent carbon buildup.

Any thoughts / experience from other Pearsons?  Particularly wide-body models like the 303?

Valor

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Re: The iron sail on a 303
« Reply #1 on: February 18, 2019, 12:00:35 PM »
Carbon is a big deal in the Yanmar exhaust elbow/mixer. Do not be afraid to run the engine hard at some point of your trip.
My 3gm30F has a continuous of 3400rpm and a 3600rpm max.I almost always cruise at 3-3200k RPM all day and I will run full throttle for a few minutes just to blow everything out at the end of every trip. Fuel is cheap, carbon and a damaged engine isn't .

My boat squats under power, how much, I'm not to sure, but I think it's because the 323 is a fatso at 13000+lbs and the prop is digging in to get the boat to move. I need a drop of port rudder to keep it going straight at 7 knots under power as well. Other than that, I have no stability issues. When the boat was over propped, I had some diesel smell and a little smoke. Since I re propped the boat doesn't smell unless I'm DDW and even then it's very light.

Check your prop while you are doing all of this. If you can hit redline your good. if you can't you could be over pitched. Makes a huge difference in the happiness of the motor and speed.

 
Michael M

MangoCats

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Re: The iron sail on a 303
« Reply #2 on: February 18, 2019, 02:42:28 PM »
I think the 303 is just as much of a fatso: 10,000 lbs for 30'3" LOA, and nearly 11' of beam.

When I took possession of the 303 there was a small puddle of oil under the engine, enough to saturate a new oil absorbing pad and still need some wipedown/cleanout.  Since then, only a drop or two has showed up on the new pad, so I'm hopeful that the oil was more spilled during service than leaking underway.

Going back now to check on how things look after yesterday's 4 hour motor-cruise, when we get back to the dock with the kids it's more an exercise of batten the hatches and check the dock lines than a full-on engine and systems inspection every time.