Help: Engine stops advancing at 1800 rpm.... stumped

[lamadriver]

Hello all you engine gurus

I am stumped and frustrated. I could use some fresh opinions.

History:

My Dix 38 Pilot is powered by a young Vetus 4.17 (Mits s4l2). I left the boat in Madagascar and somewhere between there and the Seychelles the engine became hydro locked (knockdown) and bolts that go through flange tab that mounts to the engine and then to mounting stud sheared in the block.

They were able to get the motor running after about 48 hours.

They ran the engine even though being told not to to get to the seychelles.

When the boat got to the Seychelles I had a yard take a look at the motor. I was pretty adamant that I wanted it pulled and cracked open and inspected as our next passage was to SE Asia. The yard manager kept saying it wasn’t necessary and the engine ran fine. The easy-out’ed the bolts and tightened it back up.

When I got the Seychelles, all appeared good. I neutral it ran all the way up and sounded good. Once we departed I noticed that the revs just stopped at 1600 while in gear.. There was plenty of throw left on the lever.

First I though fuel restriction. I changed the fuel water separator filter, the paper filter in the lift pump and the secondary spin-on located on the engine. No joy.

I dove the prop (auto prop) Bit dirty but nothing crazy, nothing tied up. I also yarded on the p hanger and the shaft to check the cutlass. No movement – all looked good.

Now I was thinking gear box. When it went into gear it was limited at 1600 rpm or so. When throwing it into reverse it did 2000-2100. After running for a while in forward it would inch up towards 1800. The motor sounded fine, there was no black smoke, noises etc.

Normally the engine has no problem revving in the mid -2000' and was brought up to 2900 at sea trail.

When we arrive in the Maldives, I dove the prop again, still looked good. On the trip over I noticed two things: Fuel consumption was high, and there was a good deal of suit on side of the boat.

After talking with a few people, we decided to keep going as the motor was running well and just appeared to be rev limited.

As we made passage to Malaysia, I continued to notice abnormally high fuel consumption and at arrival a huge black suit spot on the side of the boat around the exhaust.

The Transmission got harder and harder to go into forward gear. Almost to the point where you had to leave it just forward of neutral and eventually it would catch. Never a problem going into reverse. If the shaft was freewheeling, with the motor off you could throw it into gear and it would catch no problem. It was if it was an issue under load.

So It had to be the box. (ZF10). When we got to Langkawi I couldn’t get it into gear. I found a new box for about the what it was going to cost to pull, send for repair, buy the rebuild kit etc.

After pulling the old box, it was obvious it was leaking internally and it looked to me like the wrong oil had been put in previously.

New box came: Slid right in, lined up etc.

1)In order to get it to go easily into gear we had to turn the rev's down from 750 – 600 at idle. It still doesn’t seem right to me. We really had to monkey at the morse cable as there wasnt much room at either end of the thread on the lever or at the linkage

2) Now the engine revs in gear at 800 right out of gate and can go althe way up to 3K= in neutral.I about cried. Engine still sounds fine, but its like it is governed. It goes up to 1800 and just doesn’t go any more. I watched on the throttle linage at the engine, it moves the linkage about another ¼ of the whole travel and just doesn’t do anything.

For kicks I was well tied up to the dock, and wanted to see what I got with resistance. I was able to achieve 2000+ rpm. 1800 in reverse.

3) the throttle lever seems stiff and the next step is to pull apart and inspect.

Now I am starting to think there were two problems the gear box and then engine rev limiting.

Im beside my self.
Anyone have any ideas?

Injector pump? Injectors over carbon-ed?

What would cause it to become rev – limited like that?

Any one seen having to really turn down idle revs to get the transmission to smoothly engage? what does that indicate?

All opinions welcomed at this stage.

Bottle of Jack Single Barrel select for anyone who can help me correctly diagnose the problem.....

LD

[Cruisingscotts]

If you have a single lever control, its possible for the throttle adjustment to get out of wack giving different throttle ranges in ahead vs. astern. If you are getting a 1/4" more travel sounds like it is the problem. Check the throttle cable at the control lever end watch the assembly when moving it to ahead and astern, may be loose worn out etc.

[lamadriver]

Hm . Thanks. Im at work and my friend is going to take apart the lever assembly this . Its a Vetus single lever.

Im not quite sure I understand what your getting at though. I can physically see the cable move the linkage, but the motor wont advance any more.

I have a spare cable, its long enough to run straight to the motor with out routing it , figured that would be a good step to eliminate the cable.

It wont let me edit my post? Moderator?

What i meant to say was it now goes right to 1800 rpm out the gate ( not 800). where before the box change it was 1500+-.

[Lepke]

If the engine hydro locked at high rpm you could have one or more bent rods. A slightly bent rod will cause lower compression in the cylinder, a loss in power and maybe some unburnt fuel. But if the engine came loose, your alignment could be bad. That could also be the soot problem. Besides wearing bearings, a bad alignment puts a bind on the shafting and the engine has to put out more power to overcome the bind. So that could also be the rpm problem.
You get soot with a too heavy load on the engine, also from restricting intake air to the engine. A partially blocked exhaust will also limit rpm.
I usually junk an engine that hydro locked while running.