Looking for advice on Velvet Drive

[heeler]

First let me say that this is my first post, although I have enjoyed this site for a long time... I learned alot here.

I am having problems with my propulsion system on my sailboat.

When I put it in gear, I am not getting the RPM at the prop like I used to.

I have a Perkins 4-154 diesel with a Borg Warner Velvet Drive transmission.
I am not sure of the model since the tag is not on the tranny, but I am almost certain that it is a 10-17 or 10-18. According to the manuals I have looked at, the gear ratio is not 2.1:1, because of the location of the oil cooling lines. I suspect it is a 1.52:1 or 1.91:1

It is not a V-drive, it is an in-line tranny

A bit of history: The boat is a 1980, but I know the motor was rebuilt about 13 years ago, according to the former owner. I don't know if they changed or worked on the tranny, and neither does he.( he just paid the bill, which he lost )

I bought the boat 7 years ago, and have had no problems at all until this year. I went to take the boat out with some friends, of course we were all looking forward to the trip, when the problem started.

We threw off the lines, and started off slow. ( I usually will test a bit to make sure the tranny will engage before casting off, both in forward and reverse )
All was well, until I went to boost the RPM as we cleared the mooring field.
The motor would not spin faster than about 1200 RPM or so. Normally I can get 2500 RPM and more. In a word, the boat was sluggish.

We went for a mile or so, and I thought it might be the shift cable. I went below, disconnected it, and manually shifted it. No change. When it was in neutral, the engine would rev perfectly, as it has always done, but once it was in gear, forward or reverse, it would only reach about 1200 RPM, no matter if I put the throttle all the way up.

I thought it might be something wrapped around the prop. I dove under and there was nothing except a few barnacles, which I scraped off anyway. (When in neutral, I could easily turn the prop shaft by hand from inside the boat. ) I tried again, no change.

Someone suggested that it might be a fuel problem...clogged filters. I replaced all the filters, and there is fine flow coming to the high pressure pump. Still no change.

The boat goes in forward and reverse, there are no clunking or grinding sounds of any kind, I have the correct fluid in the tranny in the correct amount. ( I also tried changing the fluid, which was basically clear and red )

My latest hypothesis is that something ( a valve, perhaps ) is "stuck" inside the tranny.( I have manuals and diagrams, but I don't have a complete understanding about how these things work.) Some facts that support this theory: There was a couple of drops of that milky emulsified fluid on the dipstick plug. The fluid itself had no sign of any water intrusion, but those couple of drops might indicate condensation, which might be enough moisture to cause something to "stick" open or shut. Another possible contributing factor would be how much I have used the boat: It has been out of the water for the last two seasons, on the hard. I finally put it in this year, in July, and I took it from the yard to her mooring, a trip of about 10 miles. There was no problem during this trip. I have not taken any trips since then however, so the tranny has been idle for 6 weeks or so.

If anybody has any advice of any kind, it would be much appreciated, especially if it can save me from having to remove the transmission.

If I can think of anything else that I did, or if I try anything else, I will update my post.

Thank you for reading

[PAR]

This does not sound like a transmission issue, though it could be one of several engine issues. Run through the "usual suspects" as you would during an evaluation or comprehensive tune up. The first few things I would check would be the secondaries linkage to make sure they're opening and if the distributor is advancing timing when called for. Could as simple as a frozen advance weight or secondary linkage rod.

[anthony goodson]

On a Perkins 4-154 ? does sound more like an engine issue though.

[gonzo]

Does the engine blow black smoke? If it does then something may be causing extra friction, like a rope around the shaft. Otherwise, seems like an engine problem. Did you try to push the throttle manually to full speed? It may be out of adjustment.

[PAR]

Oops, I did a quick read and missed the diesel part. Still sounds like an engine issue though. Check fuel pump pressure with a gauge. How old is the fuel?

[heeler]

Originally Posted by PAR

This does not sound like a transmission issue, though it could be one of several engine issues. Run through the "usual suspects" as you would during an evaluation or comprehensive tune up. The first few things I would check would be the secondaries linkage to make sure they're opening and if the distributor is advancing timing when called for. Could as simple as a frozen advance weight or secondary linkage rod.

Secondaries...as in secondary fuel filter? Or is that only in a gasoline engine?

Thanks for responding.

[heeler]

Originally Posted by gonzo

Does the engine blow black smoke? If it does then something may be causing extra friction, like a rope around the shaft. Otherwise, seems like an engine problem. Did you try to push the throttle manually to full speed? It may be out of adjustment.

There is basically no smoke of any kind, maybe a puff of white on startup...but then clear. I have seen smoking diesel engines before, I doubt that is the problem. There is nothing on the shaft, I even scraped off the few barnacles when I dove on it. The shaft turns freely with one hand as it always did. The stuffing box is not binding on the shaft at all.

I did try pushing the throttle lever on the high pressure fuel pump manually, having disconnected the cable.The lever will move all the way over, but the RPM will not go up beyond about 1200 if the transmission is in gear.

Thanks for the response.

[anthony goodson]

In view of your response ,it may be a good idea to get a diesel mechanic to have a quick look at your engine ,just to check the pump linkage adjustment ,the fuel ,and whether or not it is firing on all four cylinders. Just out of interest what is the name on the high pressure pump ?.

[heeler]

Originally Posted by PAR

Oops, I did a quick read and missed the diesel part. Still sounds like an engine issue though. Check fuel pump pressure with a gauge. How old is the fuel?

Are you talking about the high pressure fuel pump? Like put a guage where the line connects to the injector?

I was actually wondering about the fuel...I had about 30 gallons or so in the tank from prior years, you know...I just add fuel when I need it. I added another 30 gallons or so this year, clean fresh diesel from a truck stop.

I may try bringing a portable tank with fresh fuel and just swap the supply line... the return would just end up in the main tank. I will be going down to the boat in a few days and that would be a relatively easy thing to try.

[heeler]

Originally Posted by anthony goodson

In view of your response ,it may be a good idea to get a diesel mechanic to have a quick look at your engine ,just to check the pump linkage adjustment ,the fuel ,and whether or not it is firing on all four cylinders. Just out of interest what is the name on the high pressure pump ?.

Just a quick response, since I have my "Diesel Technology" textbook out and I am going to try to get some insight on the subject of the pump linkage adjustment.

It is definitely a good idea to get a diesel mechanic out there, but there is not really a big rush... I am not going south for the winter! (Plus, I really am a do-it-yourselfer and if possible I would like to understand the issue ) I am not too hard-headed, though, so if ( when ) I get the mechanic out there, I will certainly post the results of the consultation.

I know it is firing on all cylinders, because I removed the lines from the injectors one by one, noting the difference in the engine sound and vibration.

I will get the name off the pump when I go down there in a few days.

Thanks for responding.

[heeler]

I have not been to the boat yet, but this give and take has been helpful. I am wondering now if perhaps the high pressure pump is at fault. If there is not enough fuel getting into each cylinder, then there will not be enough power to rev the engine if there is a load ( in gear ), but there may be enough power to rev the engine up witout a load. I think putting a guage where possible will give me more data, and it is relatively easy. There is also a local injector/ pump mechanic who is very knowledgable. I will consult him.

See you in a few days!

[anthony goodson]

The name on the pump may be Diesel Kiki ,if it is then your engine was originally intended for a Mazda pick up truck ,you might like to bear this in mind when ordering spares. You can download a workshop manual and parts list from Endeavour Manuals it is listed there as a Perkins 4-154.