Hi, I have a westerbeke 2 cyl 10hp in my 1984 Hunter 27. In neutral it will rev to 3000 rpms full throttle, under load going fwd it will only do 2400rpms. This doesn't seem right. any suggestions? thx!
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Off the top of my head
Off the top of my head I can think of a couple of easy things. Dirty bottom, dirty prop for starters. You didn't say how long you have had the boat, so we don't know if you have some history. Such as did it rev to full RPM before, did it start doing this suddenly, or come on gradually. If you will post up some more info. you would more than likely get a bunch of answers, and at least one of them would be on the money. Lots of other things to look for, from a clogged exhause elbow, to injector timing off, to fuel filters getting dirty, to bad fuel, and the list goes on. Give us some more info. and probably get the proper answer for someone with that same engine, who has had the same problem.
Off the top of my head I can think of a couple of easy things. Dirty bottom, dirty prop for starters. You didn't say how long you have had the boat, so we don't know if you have some history. Such as did it rev to full RPM before, did it start doing this suddenly, or come on gradually. If you will post up some more info. you would more than likely get a bunch of answers, and at least one of them would be on the money. Lots of other things to look for, from a clogged exhause elbow, to injector timing off, to fuel filters getting dirty, to bad fuel, and the list goes on. Give us some more info. and probably get the proper answer for someone with that same engine, who has had the same problem.
You may be a little over-propped, but 2400 RPM on a two-banger under load, with 3k WOT, seems about right to me. What is your speed over the ground? Your expectations may be a little out.
Engine RPM
I have a 1985 Volvo penta 18hp. After checking/adjusting the valve clearance and shaft alignment last year, it can go to 4000 rpm in neutral. I didn't want to run it for long fearing something may break.
In gear I can do 6.3kt at 2800 rpm with 80% throttle. About right for a 10400 lb load with a fixed two blade prop. Still got 20% in reserve just in case I need to run against the elements.
INMO I think you can do better than 3000 WOT and 2800 in gear. Depends on how much effort you maintain the iron genny, you should be able to achieve; clean fuel, clean oil, perfect valve gap and shaft alignment. Just imagine you are at 2800 WOT and heavy weather or current hit you. You need something in reserve.
The bottom condition doesn't affect your WOT rpm, only boat speed.
I have a 1985 Volvo penta 18hp. After checking/adjusting the valve clearance and shaft alignment last year, it can go to 4000 rpm in neutral. I didn't want to run it for long fearing something may break.
In gear I can do 6.3kt at 2800 rpm with 80% throttle. About right for a 10400 lb load with a fixed two blade prop. Still got 20% in reserve just in case I need to run against the elements.
INMO I think you can do better than 3000 WOT and 2800 in gear. Depends on how much effort you maintain the iron genny, you should be able to achieve; clean fuel, clean oil, perfect valve gap and shaft alignment. Just imagine you are at 2800 WOT and heavy weather or current hit you. You need something in reserve.
The bottom condition doesn't affect your WOT rpm, only boat speed.
H27 Engine
When I returned - same symptoms as you describe.
By that time it was near end of season so I waited till the boat was hauled - turned out that the marine growth on the prop had really flourished. It was cleaned and each year now Petit spray is applied and problem has never returned.
I have the same boat (1984) and had the same problem a couple of years back. It was unseasonably warm and the boat sat unused for a few weeks because I was away.
When I returned - same symptoms as you describe.
By that time it was near end of season so I waited till the boat was hauled - turned out that the marine growth on the prop had really flourished. It was cleaned and each year now Petit spray is applied and problem has never returned.
Based on what I've seen, about 90% of sailboats are overpropped to some extent. Theory Says you should reach WOT RPM in gear (most Westerbeke's this is 3000 RPM) So, 2400 is a bit low, implying you're probably overpropped (although if it DID reach higher, dirty bottom is probably the culprit). Take an inch of pitch out, should be fine. (again, Theory Says you should take out 2", but I like being a BIT overpropped - it means you cruise at lower RPM, as long as you're not overly lugging the engine, which would be indicated by overheating and black smoke)
But unless you're getting the symptoms above, you should be fine.
Hope this helps.
druid
www.druiddiesels.ca
But unless you're getting the symptoms above, you should be fine.
Hope this helps.
druid
www.druiddiesels.ca
I will try that, it had sat in Puget Sound since the end of last summer and this is the 3rd season after 2 coats of bottom paint.
This is the 3rd season with the boat. I remember the RPMs going higher than they do now but I've had some problems with the engine since I bought it. I've had to swap out the injectors, clean the fuel tank, new alterator, new modern racor primary fuel fliter, install sea strainer, had a valve job done, among the other standard stuff (oil changes, fuel filters). I am a novice at this stuff but hoping to become fairly competent. It now cruises at 4.5 SOG when it used to go 5.25-5.5 SOG.
Have to disagree
I must respectfully disagree with those who said this sounds about right. While the engine may very well turn a few more RPM in neutral than in gear, a 600 RPM spread is far more than would be acceptable. Those who say that it should turn up it max rated RPM, in gear, are correct. Other wise there is something not right. I think most sailboats are not propped correctly. And they should be. Not sure what max RPM is on your engine, but should be somewhere around 3000. I can turn 3500, with a max rating of 3400, boat empty of water, little fuel, and no provisions on board. Loaded up ready for a trip, max is about 3250 to 3300, with clean prop and bottom. Doesn't take much bottom growth to knock a hundred RPM, or two hundred off that number.
I must respectfully disagree with those who said this sounds about right. While the engine may very well turn a few more RPM in neutral than in gear, a 600 RPM spread is far more than would be acceptable. Those who say that it should turn up it max rated RPM, in gear, are correct. Other wise there is something not right. I think most sailboats are not propped correctly. And they should be. Not sure what max RPM is on your engine, but should be somewhere around 3000. I can turn 3500, with a max rating of 3400, boat empty of water, little fuel, and no provisions on board. Loaded up ready for a trip, max is about 3250 to 3300, with clean prop and bottom. Doesn't take much bottom growth to knock a hundred RPM, or two hundred off that number.
OK, at http://www.westerbeke.com/productBrochures/w10_two.pdf
it states that the engine should turn 3600 RPM, am i reading this right? I have also read that one should run at 80% of WOT rpms. right now at WOT in neutral it'll go 3000rpms and in gear 2400rpms. So, in theory, my engine should be turning 3600 rpms in neutral right? thanks again.
When we bought it in the spring of 2006 we had it hauled and painted with 2 coats of bottom paint. Since we have had divers change zincs and inspect the bottom but have not had a diver down in a year. I called one today to set up a time to scrub the bottom and change zincs.
3000 in neutral
If your engine is rated for 3600 in neutral, and only turns 3000, then I would look at something other than the bottom. Although a bottom inspection is probably in order if it has been a year. Lots of things to check, but I highly recommend the easiest ones first. Fuel, fuel filter, and on down the line. Might be to your advantage to get a hand held tach, hopefully you can borrow one, but they are not overly expensive, and make sure your tach isn't lying to you fairly early on. Check for an exhaust elbow that is partially clogged, make sure that your throttle cable is free, and is not binding, and it opens all the way to the stops.
Many, many simple things to check. Worst case scenario is injectors or injector pump, or possibly poor compression, but don't go there, till you have made certain all the little and simple things are correct.
If your engine is rated for 3600 in neutral, and only turns 3000, then I would look at something other than the bottom. Although a bottom inspection is probably in order if it has been a year. Lots of things to check, but I highly recommend the easiest ones first. Fuel, fuel filter, and on down the line. Might be to your advantage to get a hand held tach, hopefully you can borrow one, but they are not overly expensive, and make sure your tach isn't lying to you fairly early on. Check for an exhaust elbow that is partially clogged, make sure that your throttle cable is free, and is not binding, and it opens all the way to the stops.
Many, many simple things to check. Worst case scenario is injectors or injector pump, or possibly poor compression, but don't go there, till you have made certain all the little and simple things are correct.
I hate to go here because this was just beat to death in another thread... You said you changed the fuel filter? What size is the filter.: 2? 10? 30? 2 might starve your engine unless you have an electric fuel pump- which does not seem likely, though possible.
Is ..84Hunter.. and Pat B. the same person?
Since you've been through a lot of the more complex (and expensive) engine maintenance items once already, focus on the easiest (least expensive) possible causes first... Bottom condition, throttle function, etc.. When you check throttle function, make sure you're using the cockpit throttle lever to move through the full range of travel, and not just measuring at the engine end when the problem could be at the throttle lever. Ten HP isn't a lot, check bottom and prop condition first.
I'm new to this as well, but you mention SOG as your basis for comparison. IF you are in the Puget Sound, are currents a factor in your SOG performance? RPM not withstanding... Puget Sound tides and currents can be significant, I would not rely on a GPS and SOG to evaluate my speed through the water.
Dave
Since you've been through a lot of the more complex (and expensive) engine maintenance items once already, focus on the easiest (least expensive) possible causes first... Bottom condition, throttle function, etc.. When you check throttle function, make sure you're using the cockpit throttle lever to move through the full range of travel, and not just measuring at the engine end when the problem could be at the throttle lever. Ten HP isn't a lot, check bottom and prop condition first.
I'm new to this as well, but you mention SOG as your basis for comparison. IF you are in the Puget Sound, are currents a factor in your SOG performance? RPM not withstanding... Puget Sound tides and currents can be significant, I would not rely on a GPS and SOG to evaluate my speed through the water.
Dave
I will check the micron size, it's an electric fuel pump. thanks so much guys for your help, this really makes everything easier.
Hi Dave, yes, same person. It's definitly slower, i have a diver coming next week to scrub the bottom and change the zincs. again, thanks so much fellow sailors for your help.
One other thing to consider: is your Tach accurate? Might be an idea to get/borrow/rent a "hand tach" and confirm the tach is accurate. Things have to be REALLY wrong for an engine to not make max RPM in neutral. One other thing might be HP pump and/or governor...
druid
I had a 2GM20 yanmar in my last boat and on the front of it was a rating plate which noted the following: Maximum rating: 18hp@3600 rpm, Continuous rating: 16 hp @ 3400 rpm. Continuous means you can run it all day at that load. The point here is that in order to get your 18 hp maximum, the engine must be able to develop 3600 rpm. This is because power is the product of torque and speed. When I got this boat she was so overpropped that the maximum achievable rpm was 2800 which meant my 18 hp engine could only develop about 10 hp. The lack of power was not apparent when cruising in light airs but in 25 knot headwind boat speed dropped to about 2 knots, black smoke indicated the engine was overloaded and fuel consumption went through the roof. Taking 2 inches off the pitch had the effect of increasing speed in the same conditions to 5 knots indicating much increased power, no black smoke and fuel consumption reduced considerably. Interestingly the light air crusing at 2200rpm still maintained a similar speed to before. When I worked in the engine business we always checked that the engine could reach its full rpm before signing off on the warranty. This is because the modern lightweight marine diesels don't have the tolerence for overloading that the old heavy engines had. Chronic overloading will cause a failure of some sort. One common problem is the over fuelling that causes black smoke can also wash the lubricant off the cylinder bore causing serious wear.
With regard to the difference between load and no load rpm this is called "droop". Most marine diesels use industrial governors which have minimal droop. Gensets have even less droop because they need constant rpm to maintain the cycles (hz). Some marine diesels have a greater droop more like an automotive governor. I recently travelled on a Mercedes powered yacht 72hp @ 4000 rpm - we were in heavy weather with a following sea and this engine surged a great deal as the boat surfed on the waves indicating an automotive governor. An industrial governor would have controlled the engine speed much more closely. So unless you have an automotivr governor your maximum no load rpm should only be perhaps 5% more than full load with clean hull and propeller, and your full load rpm ought to be the maximum rating for the engine under the same conditions. Only by getting this right can you get the best out of your engine in every respect - power, economy, and durability.
With regard to the difference between load and no load rpm this is called "droop". Most marine diesels use industrial governors which have minimal droop. Gensets have even less droop because they need constant rpm to maintain the cycles (hz). Some marine diesels have a greater droop more like an automotive governor. I recently travelled on a Mercedes powered yacht 72hp @ 4000 rpm - we were in heavy weather with a following sea and this engine surged a great deal as the boat surfed on the waves indicating an automotive governor. An industrial governor would have controlled the engine speed much more closely. So unless you have an automotivr governor your maximum no load rpm should only be perhaps 5% more than full load with clean hull and propeller, and your full load rpm ought to be the maximum rating for the engine under the same conditions. Only by getting this right can you get the best out of your engine in every respect - power, economy, and durability.
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