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#1 2022-06-06 16:26:46

Pedro_Neira
Resigned
Registered: 2021-10-27
Posts: 14

Engine / Propeller problem

Hello to all of you,

I hope you are well.

This past week I have been sailing my Frances 26 quite a bit and have been frustrated at many points with the engine development. The boat was unable to get above 2.5 knots. I don't know if it is a problem with the engine or the propeller. The engine is a yanmar 1gm10 and the propeller is a twin blade. The rpm was 2000.

I don't know if anyone has had a similar problem or if this is normal.

Thanks

Pedro

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#2 2022-06-06 17:38:25

Charles_Grossie
Committee Member
Registered: 2017-08-10
Posts: 162

Re: Engine / Propeller problem

Hi Pedro,
The first obvious question is the state of your propeller. I presume that you have checked that it is free from weed/barnacles and of course any rope or line that may have been caught up on the shaft?
Next steps would be fuel starvation or your throttle cable being partially seized or not moving as far as it should to increase the amount of diesel.

I hope that you get it resolved.

Thanks.
Charlie.


Victoria 34 Cutter - 'Anitra'

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#3 2022-06-06 20:14:43

Jonathan_Hopper
Member
Registered: 2004-03-23
Posts: 161

Re: Engine / Propeller problem

What is the maximum rpm you can get?   If it approaches 3600 under load then there is unlikely to be anything wrong with the engine.   If it revs happily to 3600 you could be under propped.

Do you have the numbers of the prop - pitch and diameter?   Can you confirm what gearbox reduction ratios you have?

A 3 bladed prop will outperform a 2 bladed under power, but I would expect better from a 2 blade.   Clean prop as Charles says can make a huge difference.   Also could be slippage of the shaft where it is gripped at the gearbox.    Need more information for an informed answer!

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#4 2022-06-07 09:48:25

Pedro_Neira
Resigned
Registered: 2021-10-27
Posts: 14

Re: Engine / Propeller problem

Thank you for your replies Charles & Jonathan,

The propeller is an original twin-bladed propeller, I can't tell you the exact dimensions but it is the original propeller that the boat has always had. The Gear Reduction Ratio is 2.62:1. The propeller is completely clean, I cleaned it myself these days although it was not even necessary.

With the engine I can reach 3500 rpm. The problem is that from 2500 rpm onwards a very thick black smoke starts coming out of the exhaust. At 3500 rpm the boat with calm sea reaches 3.5 knots very hard.

Thanks for all the help you can give me.

Pedro

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#5 2022-06-08 21:36:39

Jonathan_Hopper
Member
Registered: 2004-03-23
Posts: 161

Re: Engine / Propeller problem

Pedro -

Apologies for more questions!

Is the hull clean?

Is this a new problem - ie. has this prop/gearbox/1GM10 combination been fine before, or has something changed recently?

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#6 2022-06-10 13:47:53

Pedro_Neira
Resigned
Registered: 2021-10-27
Posts: 14

Re: Engine / Propeller problem

Hello Jonathan,

thank you for your reply.

About your questions; Yes, the hull is completely clean as well as the propeller. About the engine it is something new since a few months ago, I had been able to set the autopilot in January at 4 knots without any problem and now it is practically impossible to get that speed with the engine.

Regards,

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#7 2022-06-10 16:45:45

Hugo_Motamelo
Member
Registered: 2016-12-24
Posts: 14

Re: Engine / Propeller problem

Ola Pedro,

I wonder if your air filter is clean! Diesel engines need a lot of air.

Regards

Hugo
Frances 26 Boreas K

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#8 2022-06-11 00:41:45

Bill_Robinson
Member
From: Langkawi, Malaysia
Registered: 2021-06-14
Posts: 110

Re: Engine / Propeller problem

Hi Pedro,
As well as checking the air filter, you should also check the exhaust injection bend for carbon build up and partial blockage. I had the same Yanmar engine, but with a fixed 3 blade prop. My Frances 26 easily reached 5 knots, in flat calm conditions. I had no rev counter, so not sure of the rpm, but there was no smoke.
Regards,
Bill Robinson.

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#9 2022-06-11 16:53:23

Jonathan_Hopper
Member
Registered: 2004-03-23
Posts: 161

Re: Engine / Propeller problem

If you can get max revs you should get the max boat performance as you have done before, if nothing else has changed.

However, is the black smoke an indication of a problem, if it is related?   The only way I can see a clean prop and hull can not be as quick is if the prop is not spinning as fast as it was, surely?   Black smoke is an indication of unburned fuel - ie the engine is struggling to produce the revs and so is over fuelled - often a feature of over propping.   But it is difficult to see your set-up can be over propped - a 2 blade and a slow gearbox speed is unlikely.    Can you check to see how free the shaft is rotating.   Perhaps there is resistance there, perhaps slippage where it is attached to the gearbox, or maybe the gearbox is not fully engaging - check the travel on the levers when you put the engine into gear.  Does the shaft have an in tact key or is it purely compression - if so is it torqued correctly - both ends (ie include the prop)? Check gearbox oil.   Failing that, perhaps you can use a strobe light to check the rotational speed of the shaft and work out if it is in the correct reduction for the gearbox.    What sort of stern gland do you have?   If an old 'packing style' is it over tightened?

It would also be well worth checking that this is the best prop for your set-up, but this doesn't sound as a likely cause of your present woes.

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#10 2022-06-14 11:24:04

Pedro_Neira
Resigned
Registered: 2021-10-27
Posts: 14

Re: Engine / Propeller problem

Hello to all,

Sorry for the delay and thank you for your kind comments.

I will check together with a mechanic all the aspects you comment. I hope it is nothing serious.

I will keep you informed.

Thanks again.

Pedro

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