Yanmar YSM12 Governor Question

[Bud22569]

I have an old YSM12 in my boat that has been rebuilt (about 150 hrs since rebuild) and has new fuel pumps. I have a Tiny Tach on it for a tachometer. I set the no-load max speed at 3150 according to the manual. I set the governor according to the manual. With this setup the engine will do about 2650 RPM when cruising under full power. Does this seem about right to you guys with experience in setting up these old engines?

I make the assumption that the Tiny Tach is accurate. It works by counting the fuel injection pulses (I think).

 

[Hermit Scott]

How much does your boat weigh and what size prop and pitch are you using?
I never hooked a tach up to mine. I changed props a few times to see what it would do to the speed. I ran the engine as hard as it could be with out it starting to spew oil, which mine would do if ran too hard too long.
I tried a 12LH10 12LH11 and 12LH12. The 12LH11 would get me over 6 knots but if any wind or waves, I'd be doing 3 or 4 knots. The 12LH10 would handle some wind and wave and still go 5 knots and 5.6 or so in calm water.
I love that little engine. It is so reliable. Just underpowered for my boat.

 

[Jalepeno]

I also installed a Tiny Tack D on my YSM12. The YSM 8/12 series is a great motor. Assuming that your propeller and hull are clean and you don’t have any fuel or exhaust elbow issues, I would suggest that you are over propped. The full load speed should be about 3,000RPM on the Tiny Tack (don’t use a hand held tack on the PTO shafts as they are slower). Your propeller is either too large in diameter or your pitch is too large. Some say that one inch of pitch reduction will increase your full load RPM by about 100 RPM and one inch of diameter reduction will increase the speed by 200 RPM.

When I bought my boat four years ago she would attain the proper 3,150 RPM in neutral and would not over heat. In gear she could not get over about 2,600 RPM (tied to the dock or running) and the high temperature alarm would come on after about 5 minutes. Boat speed was up to hull speed (6.5 kts) and the stern wave was climbing up the transom. The previous owner had the mistaken belief that he could push the boat faster in wind, current and waves with a bigger propeller but the only thing he accomplished was to burn more fuel that could only be converted to excess heat. The installed propeller was a 3 blade Campbell Sailor 13 inch diameter x 9 inch pitch. I contacted Campbell Sailor and on their recommendation had it modified to 12 inch diameter and 7 inch pitch. She can now run at the full load 3,000 RPM and a bit over 6 kts all day without overheating. I normally motor sail at 2,700 RPM and about 5 to 6 knots and consume fuel oil at about the rated 2 litres per hour.

When trouble shooting, ask yourself:
What has changed?
What was worked on last?
Has it always been like this?

 

[Bud22569]

Thanks guys for the information in your responses. The YSM12 is a small engine for a boat the size of mine. But it is adequate on an inland lake. The old engine runs fine (other than the YSM oil pump priming issue). After the engine rebuild I am overly sensitive to the old engines performance. I had been assuming that the RPM's may be based on a fuel or adjustment problem. In the last few months I removed the fuel tank and cleaned it and installed a clean-out door (the tank was not very dirty), installed a new Racor filter element and Yanmar engine filter element, and checked the adjustment for no-load max rpm and governor. The engine does not smoke or overheat.

Here is some more of my information:

The prop is a two blade 14LH10.
The boat is a 30' Seafarer, 10' beam, 8600# displacement
I sail on an inland lake. The last bottom job was almost two years ago (I have not cleaned the bottom this year).
Max motoring speed on a calm day is 5.7 knots.

The performance maybe what should be expected for the boat and prop size with a YSM12.

I appreciate the discussion with you other YSM owners.

 

[Don12364]

Using boat info from:-
http://cruisingresources.com/Seafarer_30
And engine data from:-
http://nf.broach.se/motorer/yanmar/yanmar-ysm8-ysm12-manual-eng.pdf
And free download of 'Propcalc' from Castle Marine
http://www.castlemarine.co.uk/pitch.htm

Then:-
Seafarer 30' LWL 25.6' Displ 8,600 lb YSM 12 10/12 Bhp @ 3000 rpm Gearbox ratio 1.98:1
Recommended 2 blade prop is 13" x 10" Engine rpm 2,850 boat speed 5.67kts.
Recommended 3 blade is 12" x 10".
This calculation assumes only 90% of available HP and RPM are used when 'cruising'. For full 12 Bhp and 3,150 rpm increase boat speed to 6.2 kts

BTW Campbell Sailing Props have smaller blade areas but tend to have rather thicker blades and so require more horsepower to turn. They often recommend lower pitch for the same engine speed and power.

 

[Hermit Scott]

Using boat info from:-
http://cruisingresources.com/Seafarer_30
And engine data from:-
http://nf.broach.se/motorer/yanmar/yanmar-ysm8-ysm12-manual-eng.pdf
And free download of 'Propcalc' from Castle Marine
http://www.castlemarine.co.uk/pitch.htm

Then:-
Seafarer 30' LWL 25.6' Displ 8,600 lb YSM 12 10/12 Bhp @ 3000 rpm Gearbox ratio 1.98:1
Recommended 2 blade prop is 13" x 10" Engine rpm 2,850 boat speed 5.67kts.
Recommended 3 blade is 12" x 10".
This calculation assumes only 90% of available HP and RPM are used when 'cruising'. For full 12 Bhp and 3,150 rpm increase boat speed to 6.2 kts

BTW Campbell Sailing Props have smaller blade areas but tend to have rather thicker blades and so require more horsepower to turn. They often recommend lower pitch for the same engine speed and power.

That's some advice worth paying for! Bud, why are you using the prop you have on your boat? Did it come with the boat, or did you buy that after?
Thanks for the link to the prop calculator. I am installing a 20hp in my boat to replace the ysm12. I have a few props, I was hoping one of them would work but I would just be wild a** guessing without a program like that.
Bud, Now that you are talking about the governor, I think the link to the throttle is external on the YSM isn't it? If it is I don't even have my governor hooked up!
BUT I can't get the program to run for some reason.

 

[Bud22569]

Scott, the prop is what came on the boat. It appears that it is too much prop for the boat/engine. It looks like I need to be thinking about a different prop.

The no-load max rpm and idle speed is set with the pivoting arm on the top front of the engine. The governor setting is done with the cap screw & bolt combo on the front of the engine below and to the left of the oil fill cap. See pages 4-5 & 4-6 in the YSM engine manual. The setting of the governor is based on lining up a mark on the governor rack of the high pressure fuel pump with a reference mark on the high pressure fuel pump. It's all magic to me. I just made sure I had it all setup the way the manual describes.

Donalex, thanks for the good information.

Jalepeno, I going to contact Campbell Sailor to see if they recommend a prop similar to yours. It looks like your prop works very well for you.

Thanks for all the information.

 

[Hermit Scott]

OK I remember now. The governor is internal. I have the manual on the boat right now, not with me. There is an extra pivoting arm on top so the actual throttle arm can be pulled with a spring so the governor can do it's magic and not fight against the throttle actuator cable.
You definitely want to contact Campbell for their recommended prop size. There is a post by MaineSail on the Campbell Sailor prop. That is the prop he uses. He prefers a 3 blade.
I think it is the same post that has his, prop drag testing invention video. Anyway I think he switched from a michigan wheel type prop, same diameter and blade number but the pitch was
different.