Yanmar WOT

[Mark Nooney]

I interested in knowing if any of your engines throttle up to the "published" WOT. My yanmar 2gmf is rated at 3400 rpm. The most I can get out of
the engine is 3281 WOT with no load. When you do the math is 96.5% of 3400 rpm.

So should I be worried that I am not hitting the "published" WOT??

Thanks in advance
Mark

 

[Bill1565]

I interested in knowing if any of your engines throttle up to the "published" WOT. My yanmar 2gmf is rated at 3400 rpm. The most I can get out of the engine is 3281 WOT with no load. When you do the math is 96.5% of 3400 rpm. So should I be worried that I am not hitting the "published" WOT?? Thanks in advance Mark

3281 sounds suspicious. How
can you measure that precisely?

 

[HernandoBeacher]

Re: Yanmar WOP

Prop size and pitch will determine the actual rpm obtainable. Looks like your prop is sized correctly assuming the tach is correct

 

[kloudie1]

Re: Yanmar WOP

From the RPM number, I am assuming that you are using a hand held accurate tacho and not the Yanmar one. The No Load max speed for that engine should be set at :
3750 +50, -0 RPM This is set by the governor no-load speed stop. The maximum "1 hour" speed for the engine is 3600 RPM. The maximum continuous rating is for 3400 RPM. The propeller pitch and bottom cleanliness determines whether you can get to 3400 or 3600 under load. If the governor max speed stop has sagged to 3281 then you probably will not get to anything higher.. If your boat speed under power is bothering you, get a good Yanmar guy to set up the governor correctly.. If you are a competent gear head and have a good tacho.. the procedure is not too tough but you can really do some damage if ya don't follow Yanmar's set-up precisely..

 

[Steve Dion]

Re: Yanmar WOP

Mark: You can purchase a strobe like this to check your built in tach.

http://www.amazon.com/dp/B00EDSPIES...e=asn&creative=395105&creativeASIN=B00EDSPIES

The Yanmar tachs have been reported to not being correct. Our H'31 could NOT reach max RPM's. I when from a 15 x 12 to a 15 x 10 (both 2 bladed) and was able to get about another 400 rpm's but we never were able to get to 3600.

Assuming that everything else is correct it could also be the governor.

 

[Benny17441]

Re: Yanmar WOP

No, not a source of worry. It is just an auxiliary engine and if you attain 96.5% of maximum rated RPM that is pretty good.

 

[Ken13559]

No, not a source of worry. It is just an auxiliary engine and if you attain 96.5% of maximum rated RPM that is pretty good.

But the OP said its no load max rpm. I think no load should reach >3600rpm.

 

[jmce1587]

Re: Yanmar WOP

Mark, I too have a similar problem with my 2GMF on my H31. Under hand held tach I am seeing 3200 no load. I figure for a 30 year old engine that's not bad. Unfortunately my yanmar tach is reading 2600. Investigating sending cable or possibly replacing tach itself.

 

[Mark Nooney]

Re: Yanmar WOP

Thanks Steve for the link - already have one.
Jerry -
My tack reads low also - I am using a laser tach to get the rpms.
My mechanic said I should check out the sender. If it has never been cleaned there may be "stuff" that is affecting the reading properties. The tach and the cable are the last things he suggested to change out do to the cost of the control panel. I think it's around $600.00. Not sure about the wiring harness.
.

 

[heritage]

Re: Yanmar WOP

Just to let other readers know that not all Yanmar tachs read low, mine was spot on when checked with a hand held laser tach measured at the crankcase pulley. The engine is a 3gm30 with VDO gauges.

 

[jmce1587]

Re: Yanmar WOP

Mark

Last week received the following prices from local Houston yanmar rep.
Tach-$153 and the sensor - $135

Good luck. Will let you know what I find out on my fix. I will try cleaning the sensor and then replacing before changing out tach.

 

[Mark Nooney]

Re: Yanmar WOP

Good to hear - let me know what you find.

 

[Benny17441]

Re: Yanmar WOP

Ken, "no load" figures do not move a boat. Mark does not tell us what his WOT RPM figure is when underway. Between prop size, condition of bottom and sailing conditions engine RPM may be limited. Add 30 years of use for an 84 h31 and if you get 90% of rated RPM you may be doing good. Rebuilds are expensive. The acid test would be how is the engine propelling the boat under normal circumstances. If it is doing a good job I would not worry about a small loss of RPM.

 

[Ken13559]

Re: Yanmar WOP

When I WOT my 2gm20f under no load, i could reach 3800rpm on a handheld tachometer. Yanmar tachometer is only +50rpm off from handheld one for across thee scale. Under load of 16"Dx18deg Kiwiprop, I get up to 3350rpm(Yanmar tachometer) so its about 3300rpm on handheld tachometer.
So if your Yanmar cannot achieve >3600rpm under no load, something is not right or your engine is tire and in need of "refreshing" ...overhaul.

 

[Mark Nooney]

Re: Yanmar WOP

To update all
Prop = 14X11 2 blade
WOT under load = 3059 rpm.
WOT NO load = 3281 rpm.
Measured with laser tachometer.

 

[Ken13559]

Re: Yanmar WOP

mark, when i swing the stock prop 2RH 15"Dx10"P, i could reach 3400+rpm on WOT.

 

[jmce1587]

Mark, replaced sensor and still have the same problem. Will tackle the tach itself in the next few weeks and let you know the results.

 

[Warren Milberg]

Can your engine propel your boat at 6.5 - 7 kts in relatively flat water and without significant headwind? If so, you have little to worry about. If it is significantly below that, continue looking at the tach, sender, and finally, run a compression test.