Perkins Transmission -- weak reverse
Date: September 1, 1999
From: John Bartoszek jbartosz@symbol.com
Looking for other Perkins owners experiences with engine/transmission performance in reverse. I recently had problems with my fuel system after a yard doing some repairs put about 15 gals of water in my fuel tank. Have just replaced the water seperator and low pressure fuel pump but still seem to get poor preformance in reverse. In neutral, the engine seems to accelerate fine, achieving rpms in excess of 3000 (hard to gauge because I think my tachometer is not working right). When I put the transmission in forward (while tied to the dock), the engine seems to accelerate well, reaching about 2800-3000 rpms on my suspect tachometer and provides a lot of thrust from the propeller (as evidenced by the churning of water and the strain on the dock lines). However, when I shift to reverse and give the engine full throttle, I don't get the same response The tachometer does get to about 2500-2600 rpms (but remember, I am not sure it is very accurate) but I don't "feel" the same power as when in forward. And I do recollect that, before this "water in the fuel" incident, I seemed to get a lot more feeling of thrust and engine speed when at full throttle in reverse.
I did have some trouble with the fuel shutoff after the "water" incident where it did not return to the operating position easily. I sprayed some WD40 on the lever and was able to get it to move freely again.
I did consult the yard that made the mistake (the engine mechanic does seem fairly knowledgable of Perkins engines and has been very helpful) and he indicated that the poorer performance in reverse is due to the fact that the fixed propeller is not nearly as efficient in reverse, especially if the boat is not allowed to move.
I have not looked into the transmission yet but that is going to be my next focus.
Any advice would be greatly appreciated.
Date: September 2, 1999
From: Mike Miller capnmike_s@yahoo.com
John...There's nothing wrong with your transmission...props, especially fixed ones, only perform to a fraction of their efficiency in reverse. Instead of the "bite" being on the leading edge and thrusting off the "cup", it's backwards .... One of the reasons why boats don't back up well, especially from a full stop. The engine mechanic is correct in this. Make a sketch of the hydro-dynamic of the water flow around a prop in both directions, and you will immediately see why this is so.
Date: September 2, 1999
From: Frederick VerPlank fastfredv@earthlink.net
I think the mechanic hit the nail on the head....his explanation is the most likely. If the engine gives full revs and the transmission (uh, you 'do' have a Hurth don't you?) is fully engaged... better check the linkage just to be certain.... anything other than a variable pitch, reversing Martec (or equivalent) propellor is going to be considerably less efficient in reverse. My opinion anyway... YMMV, etc.
Date: September 2, 1999
From: Robert T. McWhorter RTMLAW@aol.com
While I'm not the last word on Diesel engines, it would seem to me that the engine, being reciprocating and running, would have no ability to sense whether the transmission was in forward or reverse. It would only know whether a load was present.
As the engine runs well in forward when under a load, I thus doubt the water problem is the culprit for poor performance in reverse. I would first check the transmission, fouling on the prop and the propeller's rated performance in reverse. My conclusion would be that the problem, if any, lies aft of the engine itself.
Date: September 3, 1999
From: Phil Johnson Flipper1@erols.com
Your discussion does not mention which engine or boat you have. My experience as a marine engineer and 9 year owner of an E-40 with a 1980 Perkins 4-108 with over 5000 operating hours using a Hurt transmission is as follows: First, depending on which hand your propeller is pitched (ie. right or left handed) and which Hurt transmission you have 2, 2.5 etc., the ratios for ahead and astern operation are usualy not the same. In fact in most applications of the transmission, the ahead direction has a higher reduction than astern. The difference in ratios as mentioned above (ie higher reduction in ahead) usualy results in better stopping and astern thrust. This is because when backing, the propeller is actualy turning faster for the same engine tach reading. I have heard of E-40's who have inverted the pitch hand and the lever attachment to provide higher prop rpm in the ahead direction, but I can tell you that the manufactures application and intallations manuals show specific performance curves and that in the specifics of touque and Hp. for the 4-108 they recomend the use of their cooler.
The propeller pitch has a lot to do with the engine performance as well. An over- pitched prop, may limit the engine from achieving full RPM, particularly with reduced transmission ratios. You did not indicate if the exhaust had black smoke, lower RPM's and smoke are sure signs of engine oveloading. Now engine overloading can be due to the above mentioned reasons, or it could be as a result of reduced engine performance. A bad injector, a stop lever not fully returned to the run position, poor compression, blocked intake and many other things perminate or temporary could result in a weak engine.
If you have any specific questions, my e-mail is Flipper1@erols.com
Date: September 3, 1999
From: Sam Woolsey SamWoolsey@aol.com
John,
I have a 1983 E-40 with a 4.108M Perkins, 50 Horse engine.
1) Tachometer - My tachometer runs off of the alternator current. If your batteries are fully charged and no electricity is being produced, the squirrellyinstrument has nothing to measure therefore the Tach is . The suggested solution is to turn on a couple of lights on down below to give reason for the alternator to produce electricity and the Tach will indicate properly.
2.) Why do you need to run 3000 RPM in reverse? A sailboat is not designed to go backwards. I still have the original manuals from when this boat was new and in indentured service with Tortola Yacht Charters in Tortola, BVI. The operations manual says this about the E-40, " One thing charterers often have a lot of trouble with is handling the boat in reverse. The boat backs quite strongly to port, overriding the rudder. Even if you have the rudder turned to starboard."
3) I wouldn't come down too hard on a boat yard for any water that appears in your fuel and tank. Read all of the stuff on the Endeavour board about fuel/water tanks built into the keel. Remember the apparent bilge on your boat may actually be the top of your fuel tank. Your boat is getting on up there in years and you probably have aluminum tanks. The leaks in my tanks causing the trouble were in the top. I didn't have a bit of water in my tanks in port. When I went out for an hour or two, I would end up with water in the fuel. The source was the rudder stuffing box. When I was moving, water was forced up along the shaft into the boat and the bottom of the bilge (top of my tanks). No problem in port as the stuffing box was out of the water.
Date: September 7, 1999
From: John Bartoszek jbartosz@symbol.com
Thanks for all the responses!
For clarification, the boat is an E-40 and the fuel tank is a replacement that actually occupies the space where the 2nd water tank used to be. Also, recalling the engine performance prior to my "water" incident, the thrust in reverse was definitely better than I am currently experiencing. It now acts similar to when my propeller gets loaded with barnacles (like at the end of the season) and I know that is not the case because I cleaned and recoated the propeller when the boat was out of the water for the keel repairs.
Phil's input raised some good points. I did notice black smoke coming out of the exhaust at full throttle. His input supports my belief that there is a problem with getting adequate fuel to the engine under load and the cause is, most likely, in my injector pump or fuel shutoff. Regarding the fuel shutoff, the lever is up against the stop on the injector pump so it appears to be fully opened, unless there is a problem internally which I cannot see with the pump installed. I am having another diesel mechanic look at it this week.
Date: September 7, 1999
From: Carl Hibbard Chgypsy@aol.com
Hello John,
To alleviate one thing. The water in the fuel that you mention would not have anything to do with your feeling of poor reverse performance. If someone had crushed one of the transmission cooler lines while working on your engine you would also have problems in forward. Oh yes! I am presuming that you have not overfilled the transmission.
Due to the angle of the driveline and the proximity width/position of the keel you would not get as much water boil in reverse. This is the same reason that our boats with a full keel are such a bear to steer in reverse, as it takes to long for the water to flow along the keel. The yards statement that the fixed blade is not as efficient in reverse is correct.
Tach readings...(BTW those that you gave are quite normal). Your tachometer is a generator (alternator) driven unit. If you have wierd readings the most common problem is a loose belt. This is assuming that you have not converted to some type of "fast charge, heavy charge" arrangement, or changed the instrumentation. If you are worried that your tach doesn't read on first start until you "goose" the engine up a tad--this is normal for an alternator. Depending on the unit it won't turn on until you reach say 500 +/- rpm, which is where the voltage regulator turned it on.
John I hope that at least some of your worries have been alleviated.
Date: September 27, 1999
From: John Bartoszek jbartosz@symbol.com
Well, I found the source of my problems. Apparently one of the fuel lines to an injector was not tightened down after the bleeding process. Engine runs much better when firing on all 4 cylinders. Reverse is much better, at least as good as it has ever been. Thanks for all the input.
