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  #31  
Old 08-23-2013
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Re: what kind of headwind should a sailboat be able to motor through?

The wind velocity is less important than the fact that this engine won't turn anywhere near the expected rpm's. Running at spec, that is a decent engine for that boat, but right now she is running nowhere near spec.
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  #32  
Old 08-24-2013
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Re: what kind of headwind should a sailboat be able to motor through?

Is that 2300 RPM with the throttle right up against the stops? Check the linkage to be sure the lever in the cockpit is moving the lever on the engine the full distance.

If so, that is your problem but other things could compound it.

With the boat clean and light, as your was, the RPM should come right up to maximum continuous in smooth water and calm winds. You should check with a manual or Yanmar for that RPM but, if it is an older Yanmar, 2600 sounds right. More than 50 RPM less than this, and you are hurting the engine and it will falter under heavy load as you are experiencing.

That is a an important limit on proper pitch. You can also have the prop WOT match at the higher rating most yacht engines list as being for "one hour of operation only". This will let you move slower through crowded mooring areas, maneuver a bit better, and have slightly more ability to punch into head seas and wind. It's like being in a lower gear in your car and most people prefer it. The drawback is higher fuel consumption while cruising. Since I cruise full time, much of it under power, I prefer the higher pitch. The engine run quieter at lower RPM and the fuel savings add up.

If you are over propped, send the prop out to a shop, tell them the WOT RPM you are getting and what you would like to get. They can bend the blades while re-balancing and reconditioning and get very close to what you want. It costs less than $200 here in Maine for a prop of that size.

For the severity of what you are experiencing though, you must also check for fuel and air restriction. If it is that heavy black smoke you see trucks make pulling away from a stop, it probably isn't fuel restriction. Just be sure you aren't seeing smoke only because you look anxiously over the stern when the engine falters. All diesels smoke some and it looks heavier as you slow down because the boat isn't moving away from it as fast.

If the engine is simply faltering and slowing, it could well be fuel. The silly little tank vents they put on yachts plug with corrosion or wasp nests. Enough air can get in to run at low cruise RPM and wind load but the fuel pump can't pull against the vacuum enough to get more fuel. Old fuel lines can also have separation of inner layers and other blockages. Make sure your tank doesn't have a screen over the suction inside the tank that is getting blocked with scum. This is the time to get that tank well cleaned out. If that tank has sludge on the bottom and biofilm on the sides, that new filter you put in could have been partially plugged up again within the first hour you ran the boat. You can't just dump something from a bottle in the tank. That will just make it worse. You need to talk to a boatyard or do some research. It's a whole subject of its own. If you have inspection ports, there is nothing like rags and elbow grease.

Do you have an electric fuel pump? My tank gravity feeds and runs fine at cruise RPM but the engine begins to falter exactly as you describe (except for the smoke) if I go to full power. I've given up trying to remember to go down and turn on the electric pump and, since full power is usually something you need when a lot is going on, I just leave the pump on all the time.

Air restriction is often overlooked if your engine is in a tight space. Diesel's need lots of air. Too tight an engine box or an oil soaked foam filter element (which I think your engine has) can cause the symptoms you describe. Remove the air cleaner and leave a hatch open and run hard. If it runs properly, that's your problem

Last edited by Roger Long; 08-24-2013 at 07:05 AM.
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Old 08-24-2013
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Re: what kind of headwind should a sailboat be able to motor through?

Black smoke is the most common smoke emitted from diesel engines. It indicates poor and incomplete combustion of the diesel fuel. There are many causes, including

Incorrect timing
Dirty or worn injectors
Over-fuelling
Faulty turbocharger (ie not enough air to match the fuel)
Incorrect valve clearance Incorrect air/fuel ratio
Low cylinder compression (eg sticking piston rings or worn components)
Dirty air cleaner
Restricted induction system (eg system too small or kinked inlet piping)
Other engine tune factors
Poor quality fuel
Excessive carbon build up in combustion and exhaust spaces
Cool operating temperatures

more info;Cost Effective Maintenance - Diesel Smoke tells YOU a Story...
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Old 08-26-2013
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Re: what kind of headwind should a sailboat be able to motor through?

spent the last two days sailing in light winds.

Here are my findings: the engine will rev in neutral, and without black smoke. It will rev up to 3200 rpms in WOT.
However, in gear, its a whole other story. she will make 4.5 knots in flat calm @ 1800 rpms. that is about 3/4 throttle. BUT - any more throttle than that and she will start to smoke (black) badly, and no more speed. WOT will produce 4.5 knots, upwards of 2000-2100 rpms, and tons of black smoke.
any head wind/waves, and the boat will slow, rpms will drop, and smoke begins.

Starting time is definitely 10-20 seconds with some black smoke.
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Old 08-26-2013
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Re: what kind of headwind should a sailboat be able to motor through?

Quote:
Originally Posted by CanadianNorth View Post
Here are my findings: ...
That sounds like classic over propping but is would be very hard to get a sailboat that over propped since the propeller diameter is usually limited. Your prop would look pretty unusual, 4 blades, lots of pitch.

I think you probably are over propped but there is also some other stuff going on, possibly as a result of damage caused by the strain the engine has been under since the prop was installed.

This is beyond something you are going to get resolved in a forum, even one with a retired naval architect and designer of many marine drive trains on it. You need to have everything checked from forward flywheel nut to propeller nut.

Get a manual for the engine so you have power curves. Send the prop in for reconditioning. The company should have software to tell you the proper pitch if you can tell them boat waterline length and weight.

It's going to cost some bucks but there are no quick shortcuts here.
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Old 08-29-2013
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Re: what kind of headwind should a sailboat be able to motor through?

I have a 28 ft boat with a 13 HP yanmar 2GM - total wieght about 6,500 lbs. I usually run at 2700 RPM and get around 6 knots. We were in a narrow channel with a 30 kt headwind and 5 ft waves and our speed got knocked down to just less that 5 kts.

We did run into problems this summer when RPMs would suddenly drop to about 2000 (and speed with it) and it would start spewing white smoke. Problem was fuel related...grunge had accumulated in the bowl of the water seperator and, in the waves, it got all mixed up with the fuel and plugged the (new) filter.

Lesson's learned!
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Old 08-29-2013
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Re: what kind of headwind should a sailboat be able to motor through?

with the long(ish) starting interval, lack of power and smoke, i think you may have a compression issue. it might be a good time to have a compression test done.
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Old 09-23-2013
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Re: what kind of headwind should a sailboat be able to motor through?

this is posted on another thread, but for those following this one:

A little update for those following.

I pulled the injectors with the intention of testing the spray pattern. Long story short, I was unable to test them, but I did clean them up. There was a significant coating of carbon on them. I actually scraped it off the injectors.

To my surprise, the engine is running much better.
Now, I get no black smoke (previously I would always get some black smoke, and when I would go past about 1/2 throttle, or 1700ish rpms, I would get billows of black smoke and no power).
There was no smoke at all, and the engine started easily. The engine rpms did not drop when she went in gear, and she was able to rev up to 2500 rpms and give 6 knots.
Very surprising.

While not cured (past 2500rpms I get white smoke), there is definitely a significant improvement from before. Reflecting back, the carbon built up quickly over the 20-30 hours the engine was run this summer.... so I know there is still a problem somewhere in the system..

Thanks to all those who gave me advice.... and I think I'll keep some of that injector cleaner in my tank from now on.
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