RPMs below 1,000

paulj · Jul 31, 2013

When I need to maneuver, I idle at 1,000 rpms and shift in and out of gear...........

paulj :troll:

pk104 · Jul 31, 2013

My transmission doesn't like to shift at 1000 or higher so I do idle about 800 but my tach could be reading low because top RPM is only about 2500. Gary

mfarinas · Jul 31, 2013

JK_Boston_Catalina310 said:
Just curious how many reduce their RPMs below 1,000.

I never do because of the high vibration at even 900. I usually start at around 900-1,200 and then move it to right at 1,000. I will idle at that and switch in and out of gear at that RPM.

Looking for a little feed back from other 310 owners.

JK. The idle speed on my 310 (hull 173) is set at around 910 to 950. When I purchased IEMAYA, 3 years ago, I had the same problem of very high vibrations at idle speed. I have been adding about 10% of bio-diesel whenever I add fuel to the tank, and I have found that this has eliminated the nasty vibrations.

I only use the bio-diesel as an additive, not a replacement for petro diesel. My normal procedure is to add about half a gallon of bio-diesel to every 4.5 gallon jug. I have added as much as 15 5 bio-diesel, but I like to keep it around 10 to 12 percent. Supposed to keep the injectors and valves clean.

Tom J · Jul 31, 2013

I set my idle at 1250 rpm. The surveyor we had when we bought the boat said 1250 was too high, idle should be around 900. I adjusted the idle to 900 rpm, but she vibrated so much the straps for the heat exchanger broke. She shifts fine at 1250. Over 1400 hours on the engine, and the tranny is in good shape. I believe the engine manual calls for 1250 rpm.

iSailor · Jul 31, 2013

paulj said:
When I need to maneuver, I idle at 1,000 rpms and shift in and out of gear...........

paulj :troll:

Ditto on my 310.

rpwillia · Jul 31, 2013

900 rpm

I used to run it at 1100 to keep the vibrations down, but after I replaced the motor mounts last fall it is a lot quieter at idle at 900. It is an RCH more noisy at 1000 and then it goes down again until it get commensurately louder due to engine rpm.

I used the Sachs 1866-061-001 to replace the original R&D one. This was recommended by Jim the owner of Federal Marine Transmission http://federalmarinetransmissions.com/
and he indicated that even though it was a form fit, the 1866-061-001 was a bit stiff for our motor. Whether or not it really makes a difference, only time will tell. These motors are known to idle rough. With the new motor mounts the engine is a whole lot quieter.

Long Story · Jul 31, 2013

JK_Boston_Catalina310 said:
Just curious how many reduce their RPMs below 1,000.

I never do because of the high vibration at even 900. I usually start at around 900-1,200 and then move it to right at 1,000. I will idle at that and switch in and out of gear at that RPM.

Looking for a little feed back from other 310 owners.

Sounds about right. I start her up and then bring the idle up till the vibration settled down. 900 -1000. That is the speed I use to get on / out of the slip. Nice thing is the boat will move 5-6 slips out of gear once I turn down the fairway

oldguy · Jul 31, 2013

I'm in the midst of transmission and damper replacement at 550 hrs on the engine. The spline socket on the damper was almost completely destroyed, most likely due to idling in neutral at 800-900 rpm. I think there is a destructive torsional resonance there that is evidenced by excessive vibration. My advice: avoid long idles at low rpm. If you must idle do it at 1000 rpm and above to avoid the resonance. This repair is very difficult and expensive.

c130king · Aug 1, 2013

I also just recently replaced transmission and damper plate due to excessive wear...to the point the transmission failed while out sailing. Fortunately the winds were favorable for sailing into the harbor and into my slip.

Motor idles at 800-900 when I first start it up...throttle pulled all the way back to the stop. But as soon as the motor starts I throttle up to 1200. I detect no issues shifting in/out of gear (forward or reverse) at 1200.

I can tell a big difference in engine vibration between 800-900 and 1200...especially when standing on the top step of the stairs.

Thanks again to all who are helping us...shall we say "not so mechanically inclined" sailors...on this issue.

Cheers,
Jim

Maine Sail · Aug 1, 2013

After our engine was broken in one of the first things I did was to bump the idle RPM. I simply adjusted until it was smooth. Universal allows for up to 1200 RPM idle on these engines without harm to the gear..

Beta uses the same Kubota engine blocks but they add a "high inertia flywheel" to minimize vibration in these blocks. The Beta's are definitely smoother in my experience...

Witzend · Aug 1, 2013

yea, those low cylinder count light flywheel designs don't behave well at low RPM. This is one of the reason why we are seeing so many damper plate issues.

Concerto · Aug 1, 2013

JK, Thanks for the chart in your last post. My idle was set at 750-800 and the vibrations were very strong. After I started the engine I raised the rpm to 1200 and it would smooth out. Bumping the idle up to 1K is a lot better and if other crew members start it, they don't have to remember to raise the rpms.
Just as an aside, your chart shows max rpm as 2900-3000. I can make that engine speed but my "redline" on the tach starts at at 2500. I can hit 3000 in neutral, but when motoring out of the harbor I max it out and it runs at 2500. Then the rpms gradually slide back to 2200 where it will run all day. Very smooth and the engine seems to like this amount of effort.
Your tips and insights are always welcome and you and other association members have helped me get "Concerto In Sea" in top notch shape. Right now I think she is almost finished, and if I can keep her "almost finished" for the next ten years or so I will be a very happy sailor.
Alan Schaub
s/v Concerto In Sea #189

Long Story · Aug 1, 2013

Question to help you figure out RPM Max. Prop is it fixed or folding? If fixed 2 or 3 blade.

Concerto · Aug 1, 2013

Concerto has a three blade fixed prop.

Long Story · Aug 2, 2013

Your moving more mass through the water when you swing that prop, and also "Digging" into the water with more bite - hence, you will not run the RPM's up as high with a three blade prop, but you get more torque and power so it is a reasonable trade off

Maine Sail · Aug 2, 2013

Long Story said:
Your moving more mass through the water when you swing that prop, and also "Digging" into the water with more bite - hence, you will not run the RPM's up as high with a three blade prop, but you get more torque and power so it is a reasonable trade off

Properly sized a two blade prop and a three blade prop should reach the identical max RPM.... If you can not attain max rated RPM in calm, current free water then the prop is simply not sized correctly. This means you can't replace a two blade 15X10 prop with a 15X10 three blade. The three blade will likely need to be a 15X9 or 15X8 in order to attain the same RPM at max throttle.

Often times these alternator driven tachs are not correctly calibrated so check that first with a digital photo tach..

Concerto · Aug 2, 2013

Long Story said:
Your moving more mass through the water when you swing that prop, and also "Digging" into the water with more bite - hence, you will not run the RPM's up as high with a three blade prop, but you get more torque and power so it is a reasonable trade off

Thanks again. That makes perfect sense to me. Happy to have you people around for ideas, help and inspiration.
One thing I do notice is the world of difference between this engine and the M-15 I had in my last boat, a 1983 C-30. One of the main reasons I traded up to the '02 C-310. That and the v-berth mattress. LOL

Long Story · Aug 2, 2013

My three blade is a 15 x 8, and Maine Sail is correct as always, you need to change pitch to keep the RPM's up. I know I am still comfortable at 2600-2800, and only issue I have at max RPM, (so close to 3k you can't read the difference) is that I bury the swim platform in the water behind me...

RPMs below 1,000

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