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Old 28-06-2010, 21:05   #1
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I Thought I Fixed the Problem

For some time I have had small problems with the single lever controls (throttle and gears) on my boat. I was annoyed that while the engine was governed to 3000rpm I could only get it to about 2200. This is not a real problem because at that speed the boat is above hull speed anyway because the engine is larger than normal (35ft Martzcraft ketch with a new 35hp motor). The weird thing is that it would rev to 3000 in neutral and reverse but not in forward. So I thought... I can work this out and fix it.

I pulled the bits and pieces apart and checked them and made some adjustments by applying what I thought was logic. I carefully reassembled all the bits. There were none missing and none leftover which is a pretty good indication of approaching success for me.

Because I needed to test the revs while underway (I was not going to wack it into gear and throttle up to 3000rpm on the mooring; that would be stupid) I started the engine and checked the throttle... all worked well. I let go the mooring and returned to the cockpit to put the boat in reverse and clear the mooring. I generally just idle backwards a little and put into forward and accelerate away. I carefully made sure that I was well away from the mooring and shifted the lever into the forward gear position and accelerated.... the engine revved really well and then, in a moment of blinding and horrifying insight, became aware that I was not able to get either forward or reverse gears. The wind had blown me away from the mooring and I was now drifting slowly towards other peoples well loved and expensive bits of floating fibreglass and wood and even further away from the mooring. While I was actually speechless at this point in time a large and obscene vocabulary ran through my mind while I ran for the anchor locker and threw out the pick. I waited anxiously for it to get some purchase as I drifted ever closer to two other boats. It took what seemed like an age to dig in but dig in it did. I was too close to two other boats for comfort so I rapidly deployed a number of fenders on each side.

By now I was about 100 metres from my mooring. The one sensible thing I did was that I had kept the dinghy attached to the boat and not to the mooring. I rummaged around in the aft locker and found two lines I joined together. I attached one to my boat and then rowed back to the mooring allowing the lines to feed out on the way. When I got to the mooring I was about a metre short of rope. I grabbed hold of the mooring buoy with one hand and the line in the other and then pulled as hard as I could to try and lift the mooring chain and make fast the line. I am not as young or as strong as my imagination would like to think so it was with considerable effort I managed to join the two together.

I rowed back to the boat and used the electric anchor windlass (something I had previously fixed successfully) to lift the anchor and haul the boat back to the mooring and safety. I never anchor in the bay so as the chain was retrieved it deposited masses of black foul mud over the foredeck as additional punishment for my stupidity. Once back on the mooring I removed the entire lever assembly along with the cables to the engine and took them home to work on them on my large and well lit bench. It was only then that I could get the whole thing reassembled and realigned. I returned the following day and reinstalled installed the unit and all worked well; except that I still cannot get the engine to rev above 2400rpm (I managed to get an extra 200rpm).

So if anyone has any ideas how to fix this problem I would be pleased to hear any suggestions. The control unit is Teleflex Side Mount Sailboat Control (CH2100P) and as I said it accelerates to 3000rpm in neutral and in reverse but only gets to 2400 in forward. This I find strange because the throttle cable runs off a cam/lever mechanism that appears to deliver the same amount of movement in either forwards or reverse.

Another day on the water....

colin
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Old 28-06-2010, 21:17   #2
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The fact that you got another 200 RPM out of it says you made a difference. But largely it sounds to me that you started the whole thing to chase down a non-problem. Boats are not like cars. They are always climbing a hill. Cars get to go on the flat or even downhill sometimes. Somebody may clobber me for this, but I'd say you did good and don't know it.

The learning curve. Ya gotta hate it.
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Old 28-06-2010, 21:35   #3
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G'Day Colin,

Good story, reasonable escape from an awkward situation, but I think that you were likely chasing the wrong problem. Your symptoms sound suspiciously like either a too-big prop, a proper prop with serious fouling on it, or a foul hull. Any or all of the above can overload the engine enough that it will not reach the red line under load. The ability to get more RPMs in reverse could be due to the prop not working as well in reverse or your gearbox having a different reduction ratio in reverse (many do).

One thing to add to your knowledge: in marine diesel engines the "throttle" lever is attached to a governor, not to a thing like the throttle valve in a carburator. Thus, for any given "throttle" setting, the injector pump increases the fuel injected into the cylinders until the RPM reaches the appropriate speed and then backs off enough to just maintain the speed. So, if your throttle linkage allows your engine to reach 3000 RPM under no load then it is adjusted correctly to allow it to reach the same RPM under load -- if there is enough power available. Too great a load and it can't make it.

You might have a look at your bottom and your prop and check for barnies and such. Yeah, I just heard that it was the coldest day in Sydney for many years, so I hope that you have a good wet suit! Good luck with it!

Cheers,

Jim and Ann s/v Insatiable II lying Manly, Qld, Oz where it is slightly warmer...
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Old 28-06-2010, 22:42   #4
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Jim
This has been a problem for some time. The prop is clean and so is the hul... apart from a little slime. The crazy thing is that it will rev to 3000 in neutral... so it is not the governor, and to make things less comprehensible it will rev to 3000 in reverse! The motor is almost new and 35hp for a 35ft boat seems reasonably above the odds for power.
Its a mystery to me...
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Old 28-06-2010, 22:46   #5
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I forgot to mention that the RPM is taken off the alternator so the gearbox has little effect. I might also say that when the motor was installed it really did rev out to 3K in both directions...
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Old 29-06-2010, 00:17   #6
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Quote:
Originally Posted by Masquerade View Post
I forgot to mention that the RPM is taken off the alternator so the gearbox has little effect. I might also say that when the motor was installed it really did rev out to 3K in both directions...
Colin,

OK, clean hull, clean prop and a history of being able to reach the red line under load in the past. Hmmmm....

First, the gearbox ratios do make a difference: In reverse, some trannies have a greater reduction ratio. This means that the engine is less heavily loaded in reverse. Further, due to prop position, it could possibly not get as good water flow to it as in forward and thus not be loaded as heavily. Either of these could explain the difference you see between FWD and REV, but neither is a sure thing!

In general, your symptoms mean that either the engine is no longer producing enough power to get up to full revs or that the power is normal but the load has increased Have you by any chance loaded the boat up with more gear, water, fuel or anything to increase the weight?. If the boat is still the same, perhaps something has changed with the engine... carbon buildup in the exhaust elbow is a common means of degrading a diesel's performance.

I still don't think that there is a problem with the linkage, but if you want to eliminate it as a player, simply disconnect the morse cable from the lever arm on the engine. Should be simple to do under way... (usually just a clevis pin to pull) then rotate it by hand to the full on position and see what happens.

Anyway, hope taht you can find the culprit soon... good luck.

Jim
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