Wednesday, June 17, 2009

Engine saga continued...

Chris here... as we've mentioned before, we continue to be plagued by the engine start issue. We have replaced the starter, cleaned all of the connectors and voltage tested the battery at start. Everything seemed to point to the battery, except for the fact that our generator starts on the battery with no issue, and when we cross-connect to the house batteries the problem remains. In addition, we had an issue on the way into Florida where we increased the engine RPMs to coax some more speed out of Pelican to try to outrun the storm, but the engine temperature sky rocketed and our over temp alarm went off. When we backed down the RPMs the engine cooled down and we were good to go. Lastly, we've noticed a tiny amount of fuel and white smoke coming out of the water exhaust, and once the starter actually cranks you have to hold it for a few extra seconds to get the engine to turn over.

Today I called a mechanic in Charleston to come down and look at the engine. We're having too many issues and figured we should get them checked out. It turns out that there's a lot wrong.

First off - we seem to have found the starting issue. We put a load tester on the engine side and showed low amps to the engine. We put it on the battery side and found that the battery was fine. We put it on the positive side of the circuit and it showed good. We put it on the ground side and we found that we have a weak ground. The engine is currently grounded on one of its mounts and Yanmar recommends that it be grounded directly to the starter, so we ran a temporary cable to the starter from the current ground and she cranked correctly. So... tomorrow, we're going to run a new cable from the current ground spot to the starter (the existing cable is not long enough, so we'll jump off the engine mount) and hopefully that will solve the starting issue. The bad starter was just a side effect of overcranking, and what we thought was oil leaking out the side turns out to be varnish from the wrap on the coil (it melted it got so hot).

So now we get into the bigger issues - white smoke, fuel in the exhaust and the overheating. What I haven't said yet is that, in addition to these issues, we can't push the RPM's on the engine past 2,700 or so and the engine is rated at 3,700. Apparently, when Pelican was repowered the company didn't match the propeller pitch to the engine size to the boat requirements -or- there's something wrong with our propeller. The engine has to work too hard to push the prop to push the boat and can't actually turn the shaft fast enough to reach the appropriate RPMs. Think of it like trying to unstick a really stubborn nut. You can push with a ton of power, but the nut just doesn't turn. Our engine is pushing the prop with a ton of power, but the prop will only turn to a certain RPM.

The mechanic, Chuck, feels that we can get a new prop that will allow us to push the engine to the right point, but it will require us to run the engine at higher RPMs. Our engine is right in the middle of our living space and higher RPMs means significantly higher noise levels. He feels that the white smoke and fuel in the exhaust is due to this issue - the injectors push the right amount of fuel into the cylinders but the engine doesn't burn it because it's not turning fast enough. I might have that slightly wrong but I'm fairly certain it's close. The result is that we probably have, and will continue to have, fuel in our oil, soot buildup in our exhaust system, and ultimately soot in our injectors and our cylinder heads. From there, it will continue to build up in other parts of our system. This is what he thinks caused our overheating too - our exhaust mixing elbow is probably pretty built up with carbon and we can't run as much water through the system as we need to in order to keep the engine cool.

Soooo... we've ordered a new mixing elbow and Chuck will be back here tomorrow to replace the old one. Once we have the old one off we'll know if this is the actual problem. Regardless, it looks like we're going to have to get a new propeller and hire a soundproofing company to reduce the engine noise level. If we don't fix the root of the issue it's possible that we're aiming for a complete upper end (head) rebuild next year, and possibly a completely new engine or a complete rebuild within 3-5 years. This wasn't even on our "List" of repair items and new things we want to do, and will probably bump things like a watermaker and davits off of the list. We can only afford so much. A bit depressing, but it is what it is, and I'd rather know about it than continue to ignore the symptoms.

On another note, Aly Cat and Miakoda left the Abacos today for Carolina Beach, NC. If we can get these problems wrapped up, we're going to try to get out of here on Sunday so we can meet them there and then work our way up to Rock Hall for the end of June. I'm not overly confident that we'll be successful in this schedule with some of the weather headed this way, but we'll give it a shot. If the weather doesn't cooperate we'll be sitting in port until it gets better.

Anyway, we'll have the mechanic back tomorrow to do the elbow install and we'll see what it looks like when he takes the old one off. That will tell us a lot about the state of our engine. I'll talk to y'all then!


Wayne said...

Assuming the engine is mechanically ok and putting out its rated HP and torque, you are to size the prop so at full throttle you will be at your rated top engine rpm. Any less rpm and you are lugging the engine which will destroy it over time.
There are 2 main variables to sizing a prop, diameter and pitch. A 12 x 14 prop would read 12" diameter and 14" pitch. Other variables are cup (the curl at the trailing edge of the prop)and rake (the distance the blades are offset fore and aft of the hub). There are others but that gets complicated.
The boat and engine manufacturer should already have the correct prop selected for your hull/engine combination. Or at least what diameter is most efficient and choose a pitch to match your boat. Unfortunately, previous owners change things around, engines get changed and you don't know what was factory correct.
Bottom line - Match that max rpm!

S/V Waterfall said...

Been following your Blog for a bit, getting our own kids hyped about our trip to the Bahamas that starts next week. Chin up WRT the engine. When my wife and I lived aboard before we had kids we not only had to replace our engine when we got to NC, the replacement gave us problems (couldn't get over 1800rpms, went from Marathon to Oriental, NC top speed of 3kts!!!!). We basically memorized the ICW!!!
Maybe we'll cross paths, first leg of our trip is to Coxsackie Yacht Club on the Hudson. Heres's the link to our Blog

Take care and good luck,

Poppi said...

The engine overheating, especially at high revs, is another indicration of a blown head gasket. It could be a sticky thermostat, but with all the other indications, that is much less likely. The gasket leaking allows the combustion pressure to enter the coolant passage, preventing the coolant from doing its job. Check your manual, some diesels have cylinder drain cocks. Check them if you have any, and see if coolant comes out. I think you have a secondary coolant loop; the engine isn't cooled by seawater directly. If this is the case, check the coolant for oil/combustion products. That would be further indication of a blown head gasket. You do not want to run with a blown head gasket, as the combustion gasses will erode a groove in the head, or worse, the engine block. Heads are expensive. Blocks are... more than expensive.

Anonymous said...

IIRC, you have a Perkins 4-108? If so, if you can tell me where you sourced the exhaust elbow I'd be most grateful. Ours blew and now we can't find the part to fix it.

Currently our back up plan is to have a machine shop make us one, but that is the least cost effective method...

Anonymous said...

They don't have a Perkins. It's a Westerbeke 4-107. However, Perkins parts are easy to find. This is just one of the sites I found with the exhaust elbow you would need for hte 108.


begenning sailing said...

If you are still looking for exhaust elbo i have one, i also have many other parts for 107 or 108 motors, feel free to contact me at ( good luck in your ventures.