I read on this forum about the Yanmar, model 3gm30f 27 hp, having a sweet spot of 2800rpm's, also 3500rpm's and hitting 7 knots. Am I incorrect to think hull speed on the Hunter 356 is 5.5 Knots? I have been running at 2300 rpm's,as recommended by the dealer who sold me the boat. How fast is a Hunter 356 when sailing? when motoring? Thanks for helping a simple mind.
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Slightly low.
I think you may want to check out the Yanmar manual. They recommend that you run the engine at 70-80% of the max rated RPM. I believe that you engine is rated at 3600 rpms so that equates to 2500-2900 rpms. Remember that these tachs are not necessarily correct either. So you should run your engine in the mid range (2700)for safety. Check out Yanmarhelp.com for additional information. I think you hull speed is more like 7.5 +/- (check out this website for the specs on your boat. There has been a lot of talk about the 2 blade prop on these boats too.
I think you may want to check out the Yanmar manual. They recommend that you run the engine at 70-80% of the max rated RPM. I believe that you engine is rated at 3600 rpms so that equates to 2500-2900 rpms. Remember that these tachs are not necessarily correct either. So you should run your engine in the mid range (2700)for safety. Check out Yanmarhelp.com for additional information. I think you hull speed is more like 7.5 +/- (check out this website for the specs on your boat. There has been a lot of talk about the 2 blade prop on these boats too.
With 3 blade prop @2800
We get about 6.5 to 7 kts with NO wind pushing us around. Seems our motot purrs at 2800 rpm and I've been averaging about .6 gals/hr at that rpm. Jim S/V Java
We get about 6.5 to 7 kts with NO wind pushing us around. Seems our motot purrs at 2800 rpm and I've been averaging about .6 gals/hr at that rpm. Jim S/V Java
Recent Yanmar Class... some info
For what it is worth I'll give you the theoretical data that I received yesterday at a Yanmar class that our dealer put on for their customers. The 356 has a LWL of 30'7", so max hull speed would be just over 7.4 knots no matter what size engine you have (square root of water line x 1.34 = max hull speed). Based upon the Yanmar Fuel consumption chart for the 3GM30 engine, at 2800 rpm you should be burning around 0.79 gallons per hour. At your 2300 rpm you should be burning around .5 gallons an hour. Looks like that fits pretty well with the info that the other folks have provided. Regards, -Jim- s/v Forever
For what it is worth I'll give you the theoretical data that I received yesterday at a Yanmar class that our dealer put on for their customers. The 356 has a LWL of 30'7", so max hull speed would be just over 7.4 knots no matter what size engine you have (square root of water line x 1.34 = max hull speed). Based upon the Yanmar Fuel consumption chart for the 3GM30 engine, at 2800 rpm you should be burning around 0.79 gallons per hour. At your 2300 rpm you should be burning around .5 gallons an hour. Looks like that fits pretty well with the info that the other folks have provided. Regards, -Jim- s/v Forever
356 Speeds and fuel
I made a excel spreadsheet with speeds and fuel consumption for the 356 and the speeds are with a 3 bladed feathering prop. The other posts are generally in agreement with my numbers. Yanmar supplied me with the consumption data at various rpms. The speeds will vary motoring with waves and wind, but are good planning numbers. The hull speed is 7.4 +/- as per the previous post. If you would like a copy of the spreadsheet, e-mail me at jclark@caarchitects.com and I will give you a copy.
I made a excel spreadsheet with speeds and fuel consumption for the 356 and the speeds are with a 3 bladed feathering prop. The other posts are generally in agreement with my numbers. Yanmar supplied me with the consumption data at various rpms. The speeds will vary motoring with waves and wind, but are good planning numbers. The hull speed is 7.4 +/- as per the previous post. If you would like a copy of the spreadsheet, e-mail me at jclark@caarchitects.com and I will give you a copy.
Yanmar RPM's
I have a H356 with a Yanmar 3GM30(F). The boat is also equipped with a 2-blade folding prop. According to the Yanmar manual the RPM's could be 3400 on continous use and 3600 for short term use. At 3400 RPM's I reach the boat speed at appr. 7.4knot. At 3000 I don't. When running engine I want to get to the arrival in as short time as possible from obvious reasons. Does any one have thoughts running the engine to 3400 RPM's?
I have a H356 with a Yanmar 3GM30(F). The boat is also equipped with a 2-blade folding prop. According to the Yanmar manual the RPM's could be 3400 on continous use and 3600 for short term use. At 3400 RPM's I reach the boat speed at appr. 7.4knot. At 3000 I don't. When running engine I want to get to the arrival in as short time as possible from obvious reasons. Does any one have thoughts running the engine to 3400 RPM's?
Kjell, Don't do it.
It's hard on the boat and the engine. Belts and pumps aren't happy and engine life will shorten. (a lot) Some life expectancy numbers were posted HOW about a month ago. I don't remember the exact figures, but it was something like 'one third' of the life you would get just cruising at 80%. That continuous rating is the 'won't blow up' speed. Just use it for the tough times. Think of doing the same to your car. You wouldn't drive it at full throttle either. Your prop should be pitched to achieve max speed at max RPM at FULL throttle. Engines driven under such conditions (race cars) have to be rebuilt as often as every race. Race fans can fill in the examples. Those are my thoughts.
It's hard on the boat and the engine. Belts and pumps aren't happy and engine life will shorten. (a lot) Some life expectancy numbers were posted HOW about a month ago. I don't remember the exact figures, but it was something like 'one third' of the life you would get just cruising at 80%. That continuous rating is the 'won't blow up' speed. Just use it for the tough times. Think of doing the same to your car. You wouldn't drive it at full throttle either. Your prop should be pitched to achieve max speed at max RPM at FULL throttle. Engines driven under such conditions (race cars) have to be rebuilt as often as every race. Race fans can fill in the examples. Those are my thoughts.
do it
We've just passed the thousand-hour mark on our 4JH2E, and are absolutely convinced that 2800 RPMs is the sweet spot. With a three-blade prop at 2800 I burn .67 GPH and cruise 7.5 knots in flat calm water (with a clean bottom.) Any faster and my burn rate skyrockets. (I hit the 410's hull speed of 8.3 knots at 3400 RPMs, but use 1.5 GPH at that point. I open it up like this about once a month for five minutes just to burn the carbon out.) We NEVER cruise slower than 2500 RPMs, just to keep Mr.Yanmar happy.
We've just passed the thousand-hour mark on our 4JH2E, and are absolutely convinced that 2800 RPMs is the sweet spot. With a three-blade prop at 2800 I burn .67 GPH and cruise 7.5 knots in flat calm water (with a clean bottom.) Any faster and my burn rate skyrockets. (I hit the 410's hull speed of 8.3 knots at 3400 RPMs, but use 1.5 GPH at that point. I open it up like this about once a month for five minutes just to burn the carbon out.) We NEVER cruise slower than 2500 RPMs, just to keep Mr.Yanmar happy.
setup
I run a Michighan Dyna-Jet 18 x 14 3-blade. Engine is a 51-hp, naturally aspirated Yanmar 4JH2E.
I run a Michighan Dyna-Jet 18 x 14 3-blade. Engine is a 51-hp, naturally aspirated Yanmar 4JH2E.
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