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what kind of headwind should a sailboat be able to motor through?

6K views 37 replies 21 participants last post by  CanadianNorth 
#1 ·
Thats a broad question,

I have a 1979 Spirit, 28 foot boat with a 15 hp yanmar.

My motor idles and runs fine, up to 5 knots, with minimum headwind (2300 rpm)

However, with strong headwind 30+ knots, the boat simply cannot make headway, the engine struggles, rpms drop and smokes black smoke at times. (drops to 1200-1500) rpm at wide open throttle.

Any thoughts? it is normal for a boat of this size with this engine to be unable to tackle a headwind?

thanks
 
#3 ·
So that would be normal ? This is my first sailboat, and I only question because I have had idle/black smoke with the engine when I first bought it.
 
#4 ·
If your engine won't turn more than 2300 rpm at full throttle you may be over propped, or at least have a dirty bottom. You should be able to get at least 2600 out of that engine.
My Yanmar two cylinder will rev about 2700 when conditions are right, i.e. clean bottom, smooth water, etc. That being said I don't think she would push me anywhere into 30 knot winds without falling off and getting some sail assistance, especially with a fierce chop.
The only time I've seen smoke out of my engine was when trying to get some more speed out of the boat when she had a fouled bottom (and propellor). Just had to throttle back and live with it until I cleaned her.
 
#10 ·
That sounds right, about 500 rpm low and therefore not able to get up to the top of the torque curve/ burning fuel inefficiently.

Lots of things determine a boat's ability to head into the wind under power, including windage of stuff on deck, canvas, hull shape, etc. If you're heading into a 30 knot wind, the waves are usually holding you back more than the wind and that is a hull shape issue.
 
#5 ·
Thanks. The boat was clean when she went in the water 7 weeks ago, but it could be fouling. What length is your boat ?
 
#6 ·
Some of that black smoke may be the built up carbon getting burned up and blown out at higher rpms and hotter running temperature as well as unused fuel. Not sure about the drop in RPM after.

You don't mention the sea state or if your running against the tide, all will impede your progress.

Hows the service history for your engine? Fresh fuel filters, oil filter, oil change, valves adjusted, Exhaust hose checked for blockage? Diesel fuel clean? Tank condition? All stuff that may affect your engine running condition, especially under load. How about your hull bottom and prop condition?
 
#7 ·
The sea state was choppy, but only a mile from land with offshore winds, so not bad. No tide to speak of.
Hull and prop were clean when she went in the water 7 weeks ago.
Service history is unknown. Last two previous owners cared for the boat well - for what that's worth.
I have owned the boat two months. Previous she was on the hard 2-3 years. Its a 1979 15 HP yanmar. I changed oil, oil filter, fuel filters, new exhaust elbow (long story). Some fuel was in The tank. I had thought I drained it all, but have since run 10 gallons through.
Tank is old, no doubt. And may be an issue.
 
#14 ·
It sounds to me like the prop is too aggressive. Determine the max rpms the engine will do, whether that is a real-life test in neutral or referencing the manual. Next get it out in calm seas and get her in gear. If you have the right prop it will progress towards redline, more slowly as it gets close, finally holding steady around 200 rpm below redline. If it never comes close to redline the prop is too aggressive. If it shoots up to redline, it's not aggressive enough.
Good luck! ~LL
 
#8 ·
Maybe FSmike's suggestion about the prop is the final answer? I'd enjoy your boat as is and maybe next winter work on the prop sizing issue...You might want to find out what size props others have on their boats.
 
#11 ·
Hey,

30 kts of headwind is a lot of wind (and wind driven waves). And every kt you go forward increases the apparent wind. While the smoke is not normal, I think your performance isn't that far off. If you need to move ahead in 30 kts of wind you are going to have a hard time of it. IMHO you would be better off putting a LITTLE sail (double reefed main and small jib), bear off 40-50 degrees and motorsail your way tacking upwind.

Good luck,
Barry
 
#12 ·
I'm with Barry on this. I can't see that it's necessary to head straight into oncoming wind. even without sails just a slight tack to starbd or port will cause the boats hull windage to help it move forward.
 
#15 ·
How does she start? Ease of starting tells you a lot about the condition of the engine- hard starting with lots of smoke? Stem seals, coked up valves, head gasket, or piston rings.

you should be able to get higher revs than you are getting. as noted earlier, you are at least 500 rpm's low. Start with the cheap, easy stuff- you might want to give the lines a good bleed, and change the filter. Adjust the valves. clean the injectors. retorque the head. Get the basics out of the way before looking to the prop, etc.
 
#20 ·
Thanks for the replies.

I'm making my way along the coast of newfoundland to a cabin only 40 knots away. There are several long fjords(5 miles long , less than a mile across) with wind directly down them.

From cold, the engine smokes black when starting and takes 20-30 seconds to start. Once warm she starts no problem .
 
#29 ·
From cold, the engine smokes black when starting and takes 20-30 seconds to start. Once warm she starts no problem .
She's tired. You have a compression issue. Hopefully it's valves, not rings, and if the elbow was that badly coked up, crusty valve seats would be expected.
Start there, once you have fully bled the system with new fuel and clean filters, including the filter on the engine.
 
#21 ·
Make sure you are not stressing the engine too much. Black smoke is never a good sign. I would look at the prop issue mentioned in earlier posts. There may be a more efficient setup. Try to reduce wind resistance of your boat (dinghy, gear on deck). Try to use both motor and sail where tacking is possible.
 
#24 ·
So true.

Within a week of buying the boat the mixing elbow clogged up. It had a split in it from freezing (perhaps years ago). I hadn't seen it when inspecting the motor because of the location. Long story short, the thing leaked like a sieve and I had a local machine shop build one up. I will eventually replace it with a original part.

That said, the motor issued existed prior to he mixig elbow trouble.
 
#25 · (Edited)
I would say somthing is not quite right with your engine, as others have mentioned. Maybe valves need adjustment, maybe a fuel filter issue (also look at the screen covering the tank pick-up drop tube- could be clogged). Or could be a prop pitch problem.

In neutral, what rpm does your engine make?

I have a 34 footer with a yanmar 3GMD (20 hp) and can make 5 knots into a 30 knot head wind (with 6 foot wind swell) running only at about 2200 rpm (about 1/2 throttle). So with your slightly smaller boat and smaller engine I would think you could make say 3-4 knots under similar conditions if engine and prop were operating optimum.

One thing for sure, do not depend on your engine to get you where you want to go, because she will let you down when you need her most. Have sails and or anchor ready on stand by to get you to a safe location.

As others have said, I am thinking you are over propped. The reason is you say engine rpm drops off as head wind increases. My engine rpm stay the same no matter what the head wind speed is, the boat may slow down but the engine rpm's stay the same. I think you need a smaller pitch prop.
 
#27 · (Edited)
I have a 34 footer with a yanmar 3GMD (20 hp) and can make 5 knots into a 30 knot head wind (with 6 foot wind swell) running only at about 2200 rpm (about 1/2 throttle). So with your slightly smaller boat and smaller engine I would think you could make say 3-4 knots under similar conditions if engine and prop were operating optimum.
I find this hard to beleive. You're running 10-12 ish HP and able to push a 34 ft boat in 30 kt winds and swells at 5+ knots? Unless your in a planning hull (or other non-displacing hull), I don't see how one could do this.

I have 33 ft boat (11 ft beam) 13,000lb displ, two blade prop, and Yanmar 27 HP 3GM30F motor. I need at least 2800 RPM (85%) to make 5+ kts in 30 kt winds and 6 ft seas. Flat water, clean prop, no wind, I'm approaching 7kts at. Full throttle, I'm at 7.2 knots.

To the OP - If it takes you 20-30 seconds to get the motor fired in normal (50+ deg F) temps, and when it does, a lot of black smoke comes out, something is very amiss. Starting should take no more than 5 seconds. Mine is within 2 sec.
 
#30 ·
I get knocked down to around 4.5 knots with a 25 mph headwind in my 35 footer. In between big wave sets, she will do 5.5, almost hull speed but will average only about 4.5 once a large wave set hits. I try to keep the main up and quarter the waves. Keeping some sail up tends to stabilize the boat even if it produces next to no thrust.

I recently crossed Abelmarle Sound in a honkin headwind like this, decks awash on that ugly, shallow little body of water. It was a looooooooooooooooong, tedious f#%^ing trip!
 
#32 · (Edited)
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
 
#33 ·
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...
 
#34 ·
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.
 
#35 ·
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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