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Old 27-05-2008, 14:02   #1
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RPMS do not rise When Trans engaged

I have a Westerbeke diesel-- Starts and RPMS will climb to 3,000 under no load. When I lower the RPMS and engage the transmission, the increase the throttle the RPMS will not climb above 2,000. The force from the prop is not as strong as it was a year ago. I could run at 3,000 RPMS even though the manual says to run at only 80% throttle. I thought the trasmission was not engaging but that does not seem to be the situation. I thought the prop or shaft was entangled in line. When I moved the prop by foot, there was not resistance like being fouled by line. I checked the transmission fluid, and it seemed to be at the mark when checked cold. I just read the fluid should be hot when checked. My next thought was to change the oil. Any other suggestions on what I should check? For the past year I have taken the suggestion to engage the transmission and put a load on the engine every chance I get. So this is a relatively new problem that surfaced three months go. It was too cold to hop in the water to check out the prop until this past weekend. Yes, I realize I live in Florida and it never gets cold here. Well any water under 85% is cold to a Floridian.

John
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Old 27-05-2008, 14:09   #2
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Check your compression. As am engine wears, it loses power. Under no load it might rev up just fine, but not under load.

Are you using oil, getting gray or bluish smoke? That would reinforce the compression issue.

Injectors could also be a problem. How long has it been since you had them serviced? Again, incomplete ignition under no load my still show good revs but not with a load.

It seems unlikely to me that it is transmission related, but you could check that by pulling the prop and seeing if it will rev with trany in gear but no load produced by the prop trying to move the boat. My guess is that it will rev up much better without prop.

George
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Old 27-05-2008, 14:22   #3
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George,
I did not have any smoke last Sunday when I started it up. As I let the engine run, the RPMs increased slightly. I have not had the injectors rebuilt. The prop is a large prop. You could not do a Captain Ron move with this boat, by going full speed ahead and then putting it in reverse, because it would stall out the engine. This just seemed to happen over night. Thanks for your thoughts.

John
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Old 27-05-2008, 14:56   #4
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This can be symptoms of a clogged exhaust manifold loaded with lots of carbon. It will reduce RPMS a great deal and prevent top end RPMS all together. This is not a problem caused by the transmission as noted above. The transmission it more of a it won't work or it will. It sounds more like an inability to burn fuel properly. Someone that knows engines would give you a better clue and be able to not waste your time and money chasing things not wrong.

The last engine I saw with this problem used to be mine. To check the manifold you need to invest in the cost of a new gasket to replace it if it is not the problem. You could expect to pay a few hundred to open and replace the manifold if nothing is wrong and rack up machine charges to mill out the carbon if it was. It isn't cheap.

In any case there should be more evidence available for someone that knows what to look for. Troubleshooting an engine over the Internet isn't easy for the best experts.

My own guess is not a compression problem. If it were that bad by now there would have been a lot of problems before you got this far. A clogged manifold does creep down from your top end RPMS and sail boats get the problem easily since many owners don't want to run the engine much (I sure don't and still don't).
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Old 27-05-2008, 15:24   #5
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Paul,
Thanks for the thoughts. I just started the diesel and there was smoke. There was less smoke than two years ago. Due to the fact I am color blind, I could not tell you the color. Last Friday the RPMs max in gear were 1,800. Sunday the max RPMs were 2,200. Tonight I just ran it, and the RPMs were 2,400. I read on the forum to place the engine in gear as soon as possible to keep the cylinder walss from glazing up. So whenever I run the diesel, I place it in gear and let it warm up. Due to the age of the engine, I will be replacing the engine before I take off.

Thanks for the perspective,
John
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Old 27-05-2008, 17:02   #6
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Quote:
I read on the forum to place the engine in gear as soon as possible to keep the cylinder walss from glazing up.
Westerbekes don't exhibit that problem. It would be hard to say what to do or avoid given there is not clear problem identified as yet. You should be able to get top RPMs in gear. having too large a prop will limit that and not be sign of an engine problem but could cause you trouble down the road. The iradic nature of the problem makes it unclear what if any problem you have. A little smoke at start is not uncommon if it goes away in less than a minute or two.
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Old 27-05-2008, 17:16   #7
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Paul,
I was able to get 3,000 RPMs in gear just last year with the same prop. I had the prop reconditioned and then had the boat pulled out of the water to replace the seacocks and thru hulls. Brought it home, solved a problem with a molten ammeter, and have been rebuilding the companionway. Engine worked fine up until about three months ago when it would not reach 3,000 RPMs in gear. I am going to change the oil this weekend and see if that improves the performance.
Thank you for your comments. I really appreciate a different perspective. I want to try all the possibilities before I call the mechanic.
John
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Old 27-05-2008, 21:44   #8
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An oil change isn't going to do much if anything.

Look for the simple things first.

Fuel Filters
Collapsed/Deteriorated exhaust line (internal hose failure/backpressure)
Injectors-----carboned up
Air Cleaner (if there is one)

Remember the Triangle of Fire Fuel-Air-Heat
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Old 28-05-2008, 00:08   #9
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As chief says, oil will not cause the problem. By all means change the oil if it is due though.
I assume the prop is clean?? you didn't actually say. Paul has offered advice on a good place to check. I fixed an exhaust mixer two weeks ago. I was amazed that the engine could have ever run. 60mm exhaust size, and the blockage must have filled a good 90% of the pipe. The water exit was 50% blocked. I think the owner is going to feel like he has a whole new boat when he gets to take it out.
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Old 28-05-2008, 00:43   #10
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As the Chief said check the fuel filter as they can quickly become unwanted governors. I also think it is a fuel related problem.
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Old 28-05-2008, 02:25   #11
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Dumb question mode. Was it a year ago you had the haulout done?

What is the current condition of the bottom of the boat.

Is it heavily fouled?

Our boat exhibits the same symptoms when fouled. RPM starts to drop off along with boat speed.
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Old 28-05-2008, 14:41   #12
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Cheif Engineer, Alan Wheeler, Lancerbye, Ex-Calif--
Thanks for the places to look. The bottom and the prop are clean. Scallywag is due for a new fuel filter, oil filter, and a change of oil. There was not an air filter the last I looked but one could have been put on by the yard when I had the hoses and new circulation pump installed. If those items do not correct the problem, I will have a mechanic look at the exhaust and injectors. Thanks for the things to look for before I call an expert.
John
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Old 28-05-2008, 17:43   #13
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Unless you are getting starved for fuel - i.e. filter I think you might have to start looking deeper into the engine.

One of the most basic checks is a compression check. This will tell you the condition of the combustion chambers and a good tech will be able to determine which cylinder(s) are bad and whether it is compression rings or valves.

Good luck and keep us posted.
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Old 28-05-2008, 18:38   #14
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Ex-Calif,
Thank you for the information. I plan to change the fuel and oil filters and oil this weekend. If the situation does not improve I will call in an engine professional. From what I understand Westerbeke have cylinder sleeves. So I would have the engine rebuilt. Thakns for you input,
John
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