Cat 3126

Cat 3126

Datenight wrote:

Had the survey today of a possible Mainship 39 powered by a Cat 3126, rated at 300 hp. In the sea trial it would not go above 1900 rpm. bottom has just been cleaned and painted by me. The surveyer determined that the turbo was not coming on line and the laser thermometer showed it to be cold. You could also put your hand on it. The engine also surges at idle.

I should mention that the boat is a 2000 with 33 hours on the engine not registered since 2006. The broker wants to free up the turbo with a screwdriver (!). If he goes near it that would be a dealbreaker for me. I suspect the surging has to do with the 10 year old fuel. The Racor 900 bowl is clear but I still suspect old fuel.

Any thoughts?

Is it possibly another make of boat?

If the engine was not smoking black like a coal burning steamship it is probably not the turbo but the governor. Can you manually move the power lever on the injection pump to the high speed position? Does the engine run up to full speed in neutral? If so, does it smoke?

Remove the air filter and look at the turbo inlet, you will see the inducer, see if you can turn it with your fingertips, no tools required. If it turns freely then the problem is not enough fuel reaching the injection pump, the governor not moving the fuel lever toward high speed, or there might be air in the system. Air also causes surging. The turbo not getting hot tells me the engine is not burning fuel because it doesn't have any to burn, it would get hot whether the rotating parts were free or not if the cylinders were burning fuel.

Rick,

It does go up to 3200 in neutral. Some smoke under load but nothing like a steamship. The surveyer and I are going back Saturday to finish up. I will try your suggestions. Meanwile, the owner is supposed to have the marina's mechanic take a look at it. Will report back when I have more information.

Thanks.

Rob
37' Sedan

Datenight wrote:

Rick,

It does go up to 3200 in neutral. Some smoke under load but nothing like a steamship.

The specs say it should produce around 350hp at 2800 rpm so that 3200 is probably about right for the high speed stop on the governor. If it reaches that with no load but does not smoke under load yet can't make power then there is a fuel problem. It just isn't getting enough fuel to make power.

I think the turbo will be OK and turn freely. Have you changed the fuel filters? Check for air leaks on the suction side of the lift pump while you are looking around. The old fuel isn't a good thing but unless it is blocking the filters or the tank pickup it will just contribute to smoke and reduced power but not to the extent that you describe.

Good luck and let us know what you find.

Thanks Rick. The bowl is clear but that does not mean the filter can move enough fuel. I will check tomorrow to see if they are changing the filter. We talked about it but left it up in the air. I will also look over the fuel lines carefully for leaks.

350 hp! We have a 160 hp Perkins in our 37' sedan. I thought the plate on the Mainship engine said 300 hp. That seemed like a lot. O well, something else to check. What did you mean your first reply when you said "Is it possibly another make of boat?"

Thanks,
Rob
37' Sedan

Did the engine ever make max RPM? Maybe propped wrong. I assume she should make 2800 rpm? I have a 420hp 3126. It is supposed to be propped to make 2800. Give or take a little is no problem, but... 1900 is certainly not close enough. I would get with the manufacturer for prop recommendations.

Mine is also about a 2000 model. I also experienced the surging, which was fixed under warranty. I'll check my log book as to the exact fix.

In the meantime, I recommend to talk to a CAT mechanic about the long layup. Under use is a killer. Engines need to run.

Thanks Carey. It goes up to 3200 in neutral but not under load because the turbo would not come on line. The mechanic at the yard got the turbo spinning today but the wrong parts were ordered so could not put it back together. Looks like it will be next week before we can sea trial again.

The Cat mechanic is a good idea.

Rob
37' Sedan

Datenight wrote:

What did you mean your first reply when you said "Is it possibly another make of boat?"

Just poking fun at the sentence structiure: "Had the survey today of a possible Mainship ..."

Datenight wrote:

Thanks Carey. It goes up to 3200 in neutral but not under load because the turbo would not come on line.

I think your mechanic is scammimg you. That engine is not making power because it is not getting fuel.

If it had enough fuel, it would smoke like a coal burner if the turbo was not providing enough combustion air.

Another reason it may not make power is if there is a diagphram on the governor that senses boost pressure, if one is installed, make sure the linkage is free and the assembly works smoothly. Before investing big bucks in the turbo, apply pressure to the diaphragm if installed and see if you get more fuel. If the turbo is frozen, the engine will smoke black heavily. If nothing happens, the problem is with the fuel supply which is what it sounded like from the beginning.

Was the turbo frozen? Did you try to turn it yourself? Why is your mechanic rebuilding it? I smell something fishy here.

"Was the turbo frozen? Did you try to turn it yourself? Why is your mechanic rebuilding it? I smell something fishy here."

I am not rebuilding anything. The engine would not come up to rpm under load during the survey sea trial. Since it is not my boat, I did not try anything. The owner is having the yard look things over so we can continue. I am not sure what they are doing, was just told the wrong parts came in and we would have to wait until next week to continue. I will get a complete accounting of what they did.

I do suspect fuel as a problem since it (the fuel and boat) is ten years old with only 33 hours on the engine. Last in the water in 2006. The racor bowl is clear but as I mentioned earlier that does not mean the filter can move enough fuel. The owner is having the filter changed as well.

Rob
37' Sedan