new 1GM10 queries.

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surekandoo

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Well at long last a working Yanmar 1GM10 has been installed in Mistral.

It's very noisy, both exhaust & mechanical - various sympathetic vibrations etc. I think I'll have to get a silencer fitted in addition to the water trap plus more sound insulation.

The performance is disappointing. I retained the original Gori 13 x 9 folding prop and when I used the propcalc programme prior to the installation a gear ratio of 2.61:1 was suggested.

Both the installers and the engine suppliers did their calculations and reckoned that the std 2.36:1 ratio would be OK.

The result is that the engine will not exceed 2700rpm in gear whatever the state of wind and tide. It will reach 3600rpm flat out under no load however.

What's the problem?

Am I overpropped, overgeared or what?

Am I expecting too much - the original engine was a 12hp Vire 2T. Boat is a Feeling 720.
 
Hmm, are you sure that the original direction of rotation is correct?
My 1GM10 fitted in my Pageant is fitted with a 3 blade 14 x 10 prop and will reach 3400rpm (max revs) giving a hull speed appx 5.5 Kts (when clean bottomed and no wind/tide)
Could it be that yours is a left hand rotation prop and you are using reverse instead of forward with the gears? Sounds stupid I know, but it has been done before!!
Yanmar engines require a right hand rotation prop.
Have a search through threads I've posted when I had problems with my 1GM10 and couldn't reach max revs.
 
I'm in a similar situation. I replaced a YSM12 with a 1GM10. Yes, it's noisy but it's an old reconditioned engine. It's a massive improvement on the YSM12 but it's never going to be silky smooth. I actually don't mind the noise - it's a "proper" diesel sound that I can get used to. I do have to tweak the revs, though, to avoid sympathetic vibrations. From the dock it sounds like every other boat.

My boat is significantly overpropped and behaves as you describe. However, I can reach hull speed without reaching max revs. The big problem I fiind is close quarters maneuvering. Even at idle we will exceed 2 knots in still water. It would be nice to have more low speed control
 
mickywillis said:
Hmm, are you sure that the original direction of rotation is correct?
My 1GM10 fitted in my Pageant is fitted with a 3 blade 14 x 10 prop and will reach 3400rpm (max revs) giving a hull speed appx 5.5 Kts (when clean bottomed and no wind/tide)
Could it be that yours is a left hand rotation prop and you are using reverse instead of forward with the gears? Sounds stupid I know, but it has been done before!!
Yanmar engines require a right hand rotation prop.
Have a search through threads I've posted when I had problems with my 1GM10 and couldn't reach max revs.
Click to expand...

I didn't do the installation, it was done professionally. All the information about the prop, size & weight of the boat etc. were provided to the installers. There was no suggestion that the prop should be changed.

The engine isn't even reaching peak torque which is surprising. Will search your threads.
 
Sounds like you're over-propped, although it's possible something else is amiss; is it a new, reconditioned or used engine?
 
Last edited:
mickywillis said:
Could it be that yours is a left hand rotation prop and you are using reverse instead of forward with the gears? Sounds stupid I know, but it has been done before!!
Click to expand...

I had a Yanmar 1 GM 10 fitted in my boat by a 'Professional', and ended up motoring from Salcombe to Plymouth in reverse gear to go forward! He hadn't noticed that the old prop was left-handed! I guess he never actually gave it any 'sea trial' and going forwards with a 3:1 reduction instead of a 2:1 makes a great difference!
 
Almost certainly over propped. Taking an inch off the pitch should increase revs by around 300, but it should be propped to get around 3400 which would suggest a 13*7.
 
Tranona said:
Almost certainly over propped. Taking an inch off the pitch should increase revs by around 300, but it should be propped to get around 3400 which would suggest a 13*7.
Click to expand...

That's the conclusion I've come to, but I did ask for the engine to be geared to the prop, knowing that an alternative lower ratio was available - see original post. Would a lower gearing allowed the engine to increase revs & given better performance.

For other posters asking the engine is brand new, airfreighted from Japan. This is the second engine fitted, the first one was supplied in July with a 55a alternator as part of an OEM batch. It was discovered that the engine (not my installation) would not "get off it's knees" if the battery was flat due to alternator demand. Correct alternator is 35a. Various remedies were tried oil temp switches in the sump & relays in the alternator none of which worked on my . I mentioned "not fit for purpose" once to E P Barrus, the importers and hey presto correct engine arrives by air.

The engine does not produce black smoke even when banging into a 17knot headwind.
 
This may be useful:

http://www.yanmarmarine.eu/theme/ya...easure - datasheet/Yanmar-1GM10-datasheet.pdf

as you can see, the power at the prop is severely reduced at the revs you are reaching, by gearbox and alternator drag.

The boat is probably too massive for the engine which (in agreement with Tranona) is already overpropped.

Doubt you'd see an adequate return on any money you spent, in enhanced performance, as the Vire was considerably more powerful and had twice as many power-strokes as the 1GM10 for the same rpm.
 
charles_reed said:
The boat is probably too massive for the engine which (in agreement with Tranona) is already overpropped.
Click to expand...
Disagree. Your boat has a similar LWL and displacement to the one I had with a 1GM10 for a number of years. The engine is adequately powerful if you can get it to deliver its potential but as others have said the correct match of gear ratio and prop is vital.
 
KenMcCulloch;4345821Your boat has a similar LWL and displacement to the one I had with a 1GM10 for a number of years[/QUOTE said:
I agree. a 1GM10 drives my three tons of long keeled boat along just fine: 5.5kt flat out, comfortable cruising at 4.5kt, will keep up 4kt into a 20kt headwind. The Feeling 720 is (quick google) a wee bit shorter, a wee bit shallower and more than a ton lighter, so a suitably geared and propped 1GM10 should be fine.
Click to expand...
 
Well most posters agree that a 1GM10 should be OK for my Feeling 720.

But so that I am on sound ground with the installers, can anyone tell me whether the alternative 2.62:1 ratio would have given better performance i. e. higher engine revs under load.

The reason I ask is because when I was originally getting quotes for the supply of the engine, one Yanmar agent (in London) did actually specify this ratio after asking about the boat, prop etc. This was also borne out by my efforts with prop calc.

I went through this with the installers, they checked with their Yanmar dealer, who said that the standard ratio would be OK.

I therefore left it to the experts. A new Gori folding prop is around £6-700. This is an expense I'm trying to avoid if I can obviously.

If someone has done the calculations incorrectly, I believe I'm entitled to ask for the correct gear ratios to be supplied to replace the existing set up.

However, it may be that even with the bigger ratio, the engine will still not reach peak revs., in which case it will have to be a new prop.

Any thoughts?
 
Is a Gori folding prop more powerful than a fixed prop? Is this a 2 bladed prop? Can you alter the pitch on them? Have you tried giving the installation numbers to Gori and ask them what they recommend as a prop? If it is a 2 bladed I am surprised if you can load it up to the point that the 1GM10 struggles, but maybe the different shape of the blades does funny things.
 
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