Typical RPM

[onlinelee]

Hi all,

would members please let me know what their engines typical RPM is when at rest? I have a Volvo Penta MD2030 in my 2003 B361 and its running at 1100rpm, this seems pretty high to me? Thank you all in advance for your comments, Lee

 

[Gunni]

Hey Lee;
Here in the US, boats of that age were fitted with with Westerbeke and Yanmar engines, suggest you pose your question in the Engines forum under All Owners. The Volvo was a common engine on a lot of other boats and I am sure you can find a knowledgable owner. Had one on a J boat but that was a long time ago.

 

[JRacer]

Found a manual here: http://www.bluemoment.com/manuals/Volvo_Penta_MD2010-20-30-40.pdf

Says 850 +-25 is idle.

 

[Benny17441]

Yes, 1100RPM is a little high for an idling engine. An idling speed of around 800 RPM is more common. The thing is the tachometer or measuring device has to accurate. It looks like the manual indicates 825 to 875 and that sounds good. Diesel engines do not like to idle for long periods of time (carbon buildup) so whenever you may contemplate extended idling you may use 1100RPM as a fast idling speed. A worn engine with uneven cylinders compression may not want to idle smoothly at lower RPM so you may find some fast idlers aout there.

 

[JamesG161]

Says 850 +-25 is idle.

Boat designers typically size engines to run with a direct drive propeller to cruise at < 70% of the RPM range.
If your 29 Hp engine has a max rpm of 3000, then roughly ≈2000 rpm cruising and you should be maximum boat speed about there also.
RPM is directly related to Horse Power. Max RPM = 29 Hp delivered.
Jim...

 

[onlinelee]

Hi all,

thanks for your comments. I have the Volvo manual and should have checked it before posting. I guess its possible my tacho could be giving a false reading, maybe I should get that checked. Lee

 

[Gunni]

The sound rhythm difference between a reciprocating engine running at 850 RPM and one at 1100 RPM is easily distinguished, so once you confirm you have it right your ear will tell you everything is good.

 

[Don S/V ILLusion]

A better method would be to back off the idle adjustment until it runs 'rough' and then back up a bit. At least that's how diesel mechanics prefer it over a questionable tach.

 

[dziedzicmj]

if it is really 1100 rpm, you may risk your transmission. They don't like gear changes at higher revs.

 

[onlinelee]

When I checked it again it was in fact idling at 1300rpm!! - Well according to the tacho. I did try and adjust the idle and managed to back it off to 1200rpm, anything less than that the engine got very lumpy as Don mentioned. As I bought the boat like this and the surveyor did not flag it as a problem maybe the tacho is wrong. Next time I have an engineer aboard I will have it checked. Thanks again for your input.

 

[suttonski]

Hi, I have a Beneteau 361 year 2000 with a Westerbeke 30B3 and the idle RPM is 1150. That is exactly the idle RPM documented by Westerbeke in the verification check document that came with the engine. Max RPM is 3650.

If you lower the idle Rpm the engine will start to knock. Hope this help.

 

[SFS]

When I checked it again it was in fact idling at 1300rpm!! - Well according to the tacho. I did try and adjust the idle and managed to back it off to 1200rpm, anything less than that the engine got very lumpy as Don mentioned. As I bought the boat like this and the surveyor did not flag it as a problem maybe the tacho is wrong. Next time I have an engineer aboard I will have it checked. Thanks again for your input.

You can buy a non-contact tachometer for very little money, and check it yourself. I plan to make a correction card, like you would for a compass, if one is needed. Seems to move lower on my list every day. Soles, man, back to the soles!

 

[suttonski]

Hi I forgot to mention that I adusted my tacho with a laser tachometer so I know it is accurate.

 

[Benny17441]

The engine in question is a Volvo Penta and the manual estates around 850 RPM. What may be the possible causes of a lumpy idle bellow 1200 RPM? 1) valve lash needs adjustment, 2) uneven compression between cylinders due to wear, 3) obstructed exhaust mixing elbow 4) dirty injectors. It is best for the engine and transmission to establish the root of the problem.

 

[Jalepeno]

You can buy a non-contact tachometer for very little money, and check it yourself. I plan to make a correction card, like you would for a compass, if one is needed. Seems to move lower on my list every day. Soles, man, back to the soles!

You can also download a free app for you smartphone.

 

[SFS]

Wow, cool. Wait, how would that possibly work? The camera would be involved I guess, but what else would be going on?

 

[JamesG161]

what else would be going on?

Think Radar, but use a reflective strobe.
Jim...

 

[onlinelee]

The engine in question is a Volvo Penta and the manual estates around 850 RPM. What may be the possible causes of a lumpy idle bellow 1200 RPM? 1) valve lash needs adjustment, 2) uneven compression between cylinders due to wear, 3) obstructed exhaust mixing elbow 4) dirty injectors. It is best for the engine and transmission to establish the root of the problem.

Thanks Benny, will talk to an engineer about this. Will also find and download the App, Lee

 

[onlinelee]

Update... I spoke to the previous owner of my boat, he informed me that 6 months before I bought the boat the engine was totally rebuilt and that the hour gauge did not work and the tacho showed about 500rpm more than actual. He said the whole instrument panel was rather expensive so decided not to replace it.

 

[Guan]

My 2001 B361 Westerbeke 30B3 idles smooth at 900-1000. Was told that's too high so reset to 600 by a mechanic from a well known company.
That resulted in a long series of great advice from members..see '..engine doing the Elvis..' Finally reset idling to 1000 n it's heavenly peace again!
Although its a Westerbeke guess same goes for Volvo if it's smooth then it's ok!
Guan