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jimmy
08-09-2009, 04:51 PM
I've just replaced the volvo MD2/2B in my 32' wooden sailboat with another one. Although the engines are almost exactly the same, one difference is that the new one (new to my boat anyway, it might actually be older) has a very strong spring in the throttle control that pushes it back toward idle. I was concerned about this when I was considering doing the swap and asked for information in an engine forum and was assured that the friction in contol levers would be enough to keep the throttle in the same place or that I could use something like a friction throttle cable or hand throttle.

I now have the engine in and even after tightening up the screw in the controls that adjusts the friction as much as I can, it still won't stay at anything much above idle, the lever just springs back. So now if I want to go anywhere with the engine, I have to hold the throttle lever the whole time. I doubt that is what people did with these engines so I'm hoping somebody has a solution or somebody who has one can tell me how theirs is set up. I've asked a few places about a friction throttle cable and they didn't know what I was talking about.

If anyone has any ideas I would love to hear them

Canoeyawl
08-10-2009, 10:08 AM
Interesting...
The governor has to work against that spring, are you certain it is original?
If not, it may cause undo internal wear on those delicate little governor parts.

willmarsh3
08-10-2009, 10:14 AM
Having to hold the throttle at all times is definitely not normal.

I used to have an MD2B. It had a spring on the throttle cable much as you described. On mine it was a spring on a tube assembly that was screwed into a standard teleflex threaded cable end. In my case there was sufficient friction in the throttle lever. You could unscrew the assembly and find another way to attach the cable to the engine or remove the spring from the assembly. It is held on by a sort of flexible washer that is pressed on. I don't know the correct technical term for that washer. Or in the worst case change out the throttle control mechanism.

Andrew Craig-Bennett
08-10-2009, 10:37 AM
Interesting; I have an MD2 and the spring is really quite light - I have quite a lot of friction on the throttle lever. I'd suggest adding a fibre washer to the throttle lever assembly to add friction.

Timex
08-10-2009, 11:15 AM
Could you post a photo of the engine side?
And what model of throttle, do you have?

Tim

http://i149.photobucket.com/albums/s80/timex_timex/image-2-1.jpg

Gezzunder
08-10-2009, 11:41 AM
I'm just about to rebuild one of these (finding parts and info is murder!) so I'm wondering if I'm missing something here..

Can't you just replace the spring with a lighter version? On mine it is around the spindle for the throttle butterfly and is very light, maybe two or three pounds - certainly not enough to work against the cable.

There used to be a nifty users forum for these here (the forum portal has been hijacked by some rabid anti-american it seems)http://www.mb2a50s.co.uk/forum/showthread.php?tid=43
this post has a decent pic... 16.jpg which you need to register to view unfortuantely. Or you can see it on page five of the manual
you can download here http://www.mb2a50s.co.uk/asset/download/mb2a50s-manual.pdf

hope it works and helps

lol, wrong donk... disregard all the mb2a50 stuff, question about replacing spring remains however :o:o:o:o:o:o

willmarsh3
08-10-2009, 11:49 AM
After thinking about it some more it seems the most sensible solution would be to get a throttle intended for this engine e.g. one with more built in friction. Or get a lighter spring as Gezzunder suggests.

Apparently the spring is needed to help control the throttle. My new Westerbeke has a spring built into the engine throttle lever so it doesn't need one on the cable.

jimmy
08-10-2009, 01:48 PM
I was kind of hoping somebody could tell me what kind of controls were meant to be used with this engine. I assumed it was the controls in my boat since I had pretty much the same engine before. The spring is in the engine itself, not the throttle cable. I was told by somebody on a diesel engine forum that I couldn't remove the spring, but that is also one of the people who told me that the friction in the throttle control would be enough. My old engine and a newer MD11C don't have a spring at all and the control arm will just stay wherever you put it. Now that the engine is in the boat it would be a huge pain to try to take that part of the engine apart to change the spring if it is possible.

John B
08-10-2009, 02:42 PM
Oppose it with another ( lighter) spring or springs to get some balance.
Morse also have a nasty little fix which involves a small bracket which essentialy crushes the cable to induce more friction.Its a standard part specifically for this issue but to my mind it must induce premature wear in the cable .

jimmy
08-10-2009, 04:17 PM
I went down to the boat hoping there would be a sping under the control arm on the engine that I could take out, but there isn't. There is a photo of where the cable attaches to the engine here:
http://cid-d5341d4cceb5e207.skydrive.live.com/self.aspx/engine/P8101949sm.jpg

And the controls look a lot like this.
http://www.jamestowndistributors.com/userportal/woeimages/Engine/9533.jpg

The opposing spring idea is interesting, but doesn't that just mean it would be difficult to move in either direction or that it would snap back to half throttle or something?

Chris Coose
08-10-2009, 04:51 PM
If I think of it I shall take a picture of my original for my MD1.
It has large composite washers that have been changing in their composure over the years. The rain will swell them and then they dry and the large spring has it's way with the throttle.
I need to keep a spanner nearby to make an adjustment on the friction nut about each time I set out.

Timex
08-10-2009, 05:40 PM
From the image, you have a MJB STYLE CONTROL.

MECHANICAL SINGLE ACTION MJB THROTTLE (http://www.downloadingfiles.co.uk/teleflexfiles/library/instructionmanuals/055000-609%20MJB%20Update.pdf)
The link above is for the Manual.

Teleflex has their whole library on-line, just scroll down to Single Mechanical Action, 2nd to the last choice.

Teleflex Library on-line (http://www.teleflexmarine.com/cgi-bin/library.cgi?site=enginecontrols&type=us&library=1017)

Or...........as John B, wrote about.

A Cable Brake.
You can get them from Jamestown Distributors, for $20.

Click below for their web page, on the item.
http://www.jamestowndistributors.com/userportal/show_product.do?pid=9534


http://www.jamestowndistributors.com/userportal/woeimages/Engine/9534.jpg

Tim

Dale Genther
08-10-2009, 07:37 PM
Better than the cable brake shown above is two or three bulldog clamps. Put more than one of the proper size on the cable so the pressure exerted is spread out over a greater area, helping to prevent premature cable wear.

John B
08-10-2009, 08:35 PM
Thanks Tim , thats the unit. As I said , I don't particularly like it but thats the commercial fix for the issue.


I went down to the boat hoping there would be a sping under the control arm on the engine that I could take out, but there isn't. There is a photo of where the cable attaches to the engine here:
http://cid-d5341d4cceb5e207.skydrive.live.com/self.aspx/engine/P8101949sm.jpg

And the controls look a lot like this.
http://www.jamestowndistributors.com/userportal/woeimages/Engine/9533.jpg

The opposing spring idea is interesting, but doesn't that just mean it would be difficult to move in either direction or that it would snap back to half throttle or something?

Jimmy, disconnect the cable from the throttle body and add another suitable spring so that it assists the throttle opening but does not overcome the stock spring. what you're doing is adding a counterweight , a bit like a sash weight on a sash window. Make it too strong and the throttle could go WOT and you can't have that ( even though its unlikely with the cable connected), So just add tension till the throttle looks like its about to open and then back off the tension.

jimmy
08-12-2009, 11:23 AM
Thanks for the ideas. I will try a combination of things including the spring and cable clamps as well as trying to improve the geometry of the cable a bit. What I can't figure out is why the spring is so strong. Even the spring loaded throttle in cars isn't that strong and you push against those with your foot. This one is so strong that I worry about breaking something when I try to push it to full throttle. Thanks for the ideas.
James

seo
08-12-2009, 03:55 PM
This isn't a throttle like you might think of it in a gasoline engine with a carburetor with a butterfly throttle.
On this diesel the speed control lever works against a spring inside the governor. The governor is an old-fashioned flyball mechanical and it's what actually moves the injector rack.
There may be quite a bit of difference between how the speed control feels when the engine is running vs. stopped. But it sounds as if you have had the engine running, and found the return spring tension was too high.
As I remember that injection pump, the speed control lever had a return spring that was wound around the shaft of the lever. It's possible that the person who installed the spring put too many turns on it, therefore too much tension.
It would be good to see a picture of what you've got, and also of the same parts on the old engine.

jimmy
08-14-2009, 12:44 PM
There is a link to a picture above, but you can't really see anything since the spring is internal. I understand throttle isn't the right term, but assumed everyone would know what I was talking about. I understand the governor is not something that should be messed with if it can be avoided, and now that the engine is in the boat, it is a very difficult area to work on so I think I will try the control modifications before I resort to thinking about openning it up.

Canoeyawl
08-14-2009, 03:56 PM
Be advised that if you use the cable clamps - not only will these ruin a good cable assy (not cheap) but the added friction will increase the tension on all the parts, including the controls.

seo
08-16-2009, 01:07 PM
I think this type of engine, the Volvo, Saab, etc vertical single and twin diesels were originally intended for open launches, and there was no particular effort made to make them easy to service when crammed in under a bridge deck and cockpit. Oh well.
I have had to take apart Bosch injection pumps in situ, and it's not so bad IF YOU'VE DONE IT BEFORE ON A BENCH. So from that point of view, I'd suggest that you open up your old engine, and see what's in there. There are two big nuts on the back that as far as I remember gave access to running adjustments. This was all almost 30 years ago...
As I remember, you can remove the back cover of the injection pump, and get at the speed controller (aka "speeder") linkage to the governor. The speeder shaft has got an o-ring or lip seal to keep water from running down the shaft into the engine, and the return spring is down below. The governor is right there, and you can manually lift the flyballs, watch the rack slide, like that. Don't get junk inside, DO NOT FOOL WITH THE RACK AND PUMP ELEMENTS.
Unless it's from your junked engine, in which case you can take one apart and marvel at the manufacturing involved.

jimmy
08-22-2009, 01:12 AM
Be advised that if you use the cable clamps - not only will these ruin a good cable assy (not cheap) but the added friction will increase the tension on all the parts, including the controls.

Yes, that is exactly what I was worried about since you have to use a lot of force, and it seems like this would only increase with the cable clamps, however, nobody has come up with a better idea.

Seo, taking the old one apart is a great idea, except the old one doesn't have a spring, so it wouldn't help much other than for practice. I actually took the back cover off while the engine was out of the boat, but it wasn't obvious to me where the spring was and I was assured by a mechanic that it wouldn't be a problem, so I put it back together rather than messing with it. That same mechanic advised me to try cable clamps.