I have twin yamahas 300 on my 306 canyon. I normally run between 3500 and 4500 rpm. Question should I be running faster like over 5000 for engine heath?
Engine speed Question
- Thread starter Karen Ann IV
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I find this question to be interesting because I've heard the same thing about ideal rpm range for engine efficiency. It seems to me that if you make the same comparison to a car engine - the car engine runs on the freeway at about 2500 rpm. But on acceleration or downshifting going up a hill, the engine will occasionally go up to 4,000 to 5,000 rpm. Or put another way, the engine will experience varying rpm's under different conditions.
On a boat, you also have varying rpms when getting on plane, occasional high-speed runs or cruising. At cruise the 3,500 to 4,500 rpm range seems right to me, especially to get reasonable fuel economy. Of course, you don't want to be over propped to allow the engine to exceed the red-line. It seems to me, that like a car engine, exercising a boat through various rev ranges will be best for the engine. And avoiding consistently low or high rpms for long periods should also be best for the engine.
I'm no expert, so I'll be interested in other member's comments.
On a boat, you also have varying rpms when getting on plane, occasional high-speed runs or cruising. At cruise the 3,500 to 4,500 rpm range seems right to me, especially to get reasonable fuel economy. Of course, you don't want to be over propped to allow the engine to exceed the red-line. It seems to me, that like a car engine, exercising a boat through various rev ranges will be best for the engine. And avoiding consistently low or high rpms for long periods should also be best for the engine.
I'm no expert, so I'll be interested in other member's comments.
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Sardinia306Canyon
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Same i do all my boating life and never had a issue. This argument may be a bit different with two strokes but i see no need at all running 4 strokes at sustained 4500+.
However, there is one big difference to car engines, car engines run much more hotter than outboards but honestly i don't think that this makes a big difference.
Well some times with glassy sea i do a few miles at WOT just before the Marina to have turn them well and enjoy the breeze.
Chris
However, there is one big difference to car engines, car engines run much more hotter than outboards but honestly i don't think that this makes a big difference.
Well some times with glassy sea i do a few miles at WOT just before the Marina to have turn them well and enjoy the breeze.
Chris
Don't confuse RPM at WOT (Wide Open Throttle) with normal cruising speed.
You are fine cruising at 3500 to 4500.
If seas allow and you don't mind burning more fuel, go faster if you'd like.
For best long term engine health your props and engine height mounting should allow your motors to reach 5000+ RPM at WOT when trimmed out to their maximum angle before "blowing-out" on flat open water.
SkunkBoat
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When you are breaking in new motors( first 20 hrs) , time at various rpm matters. After that, just use the motors as conditions warrant and where you feel comfortable.
You probably red line at 6000. The motors are made to run at 5000 for hours.
You probably have a gauge or Multifunction screen that tells you instantaneous MPG (total of both engines). Look at that. You will find that number will flatten out as you get to the 3500 to 5000 range.
Your speed will be faster at higher RPM. If you get the same MPG at 5000 as 4000 but you are going faster...do that.
This particularily matters if you are running 90 miles...
It has been my experience that I get the same MPG at 33 mph as at 27 mph. That saves a lot of time over 90 miles without burning more fuel.
Sea conditions willing, go faster until it starts hurting MPG.
Yes, once in awhile "blow the dust off", go WOT in a wide open flat calm river or bay. Remind yourself why you don't like going that fast.
You probably red line at 6000. The motors are made to run at 5000 for hours.
You probably have a gauge or Multifunction screen that tells you instantaneous MPG (total of both engines). Look at that. You will find that number will flatten out as you get to the 3500 to 5000 range.
Your speed will be faster at higher RPM. If you get the same MPG at 5000 as 4000 but you are going faster...do that.
This particularily matters if you are running 90 miles...
It has been my experience that I get the same MPG at 33 mph as at 27 mph. That saves a lot of time over 90 miles without burning more fuel.
Sea conditions willing, go faster until it starts hurting MPG.
Yes, once in awhile "blow the dust off", go WOT in a wide open flat calm river or bay. Remind yourself why you don't like going that fast.
Don Davis
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I have a very good friend that was a car/truck mechanic for almost 40 years, I asked him why boats need much more RPM to reach far less speed than a vehicle. He explained that a boat is under constant load due to the resistance of water on the hull. So technically an outboard is always working harder and needs to run at higher RPM even to hold 30 MPH, I do like to run at WOT every so often just to “burn the carbon out” but I have have wondered if it’s really necessary with today’s modern EFI technology. Don’t get me wrong as it’s fun in the sun when the water is like glass but I’m soon reminded that it burns a ton of fuel as well.
I occasionally will run wide open for a few minutes, not to clear carbon, I use additives for that in my 2 strokes, but rather to scrub the hull of soft growth.
I agree that modern engines manage combustion much better than older motors.
Now if you run at low speeds like trolling for long periods, it makes sense to me to run ay speed once in a while. There is nothing magical about the WOT revs. In general by design todays engines are happiest running at 80 to 90% of the WOT figure. That of course also depends on the hull design and the propping.
I agree that modern engines manage combustion much better than older motors.
Now if you run at low speeds like trolling for long periods, it makes sense to me to run ay speed once in a while. There is nothing magical about the WOT revs. In general by design todays engines are happiest running at 80 to 90% of the WOT figure. That of course also depends on the hull design and the propping.