[JimmyK]

You usually can get a torque wrench on most of them, crow’s foot helps.  If you’re a professional mechanic and have been torquing to specs for 25 years not likely necessary but if you’re a weekend warrior, I like to get them all ‘pretty tight’ by hand and torque the ones that I can get the torque wrench on to spec and use that muscle memory to do the ones only a box wrench will fit on.  I always re-check after a good run as things move a bit after a high heat cycle.

[JimmyK]

One simple thing…use the plunger on the lift pump to prime the fuel supply lines.  If you’re not losing prime then pressing the plunger will result in an immediate ‘squeak’ from the check valve on the return side.  If it is losing prime then it will take a few (or more) pumps to get it to firm up and start squeaking.  Pump it until it squeaks before a cold start and see if it has any impact.

[JimmyK]

I have a lot of experience looking at failed metal parts.  That looks like there was a defect at or just below the surface at the 9 o’clock position which caused a stress riser.  Looks like it made quite the mess.  It looks like you have decent access to the front of the motor which is fortunate.

[JimmyK]

Exhaust gasses easily exceed 500F.  Could have warped the fiberglass tube as well.

[JimmyK]

In addition to cooling the engine coolant via the heat exchanger, the raw water also cools the hot exhaust gasses in your exhaust system/muffler.  You likely cooked the hose that is now leaking.  I would also make an effort to inspect the rest of the exhaust system that goes from the muffler to overboard.

I don’t see what draining the muffler here will do.

[JimmyK]

Ouch.  I think your idea of cutting the lower flange head bolt off and then replacing with a hex head bolt & washer is a good one.  I would do that before pulling the engine out to change the pump!  What a painful design!

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Graham A

[JimmyK]

No, there should not be water there.  Are you sure you’re using the correct o-rings?  Are you pressure testing the aftercooler after reassembly?

[JimmyK]

If the seawater side of the aftercooler were clogged enough to cause performance problems, the first place you would see that is on your coolant temperature gauge.

[JimmyK]

A minor coolant leak at the turbo-exhaust manifold interface could definitely demonstrate thick white smoke upon restart.  Bottom line is you need to locate the leak.

[JimmyK]

Could be lots of things that might be getting a tiny bit tired at 4400 hrs.

If you go from low speed running to high speed running, back down to low speed, and then immediately back up to high speed, is the same amount of black smoke present during the 2nd run up?

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Andre Huizing

[JimmyK]

I think sticking a screwdriver across the terminals as part of a troubleshooting process is a bad idea.  If you’re going to do that make sure you are wearing safety glasses.  Friend of mine lost sight in one eye from something similar.

Use a multimeter, much safer and more informative.  Check for 12v between ground and one of the big studs, if yes then check for 12v across the small terminals when the key is turned, if yes then check for 12v on the other big stud when the key is turned, if the first two are yes and the 3rd is no, you have a bad mag switch.  Any other combination of yes/no’s then the problem is elsewhere.

[JimmyK]

Interested to hear responses as well as your experience.  I have an annoying drip that I believe is the rear main seal as well, so I’ve been monitoring it but also mentally planning for the day it needs to be changed.

One thing I would definitely do at the same time on mine are the rear motor mounts (would actually do all four) as they’re old at this point even though still serviceable.

Please post your experience here if you move forward with the repair.

[JimmyK]

Any good prop shop should be able to help guide you on dialing in the numbers.

Also think it’s disingenuous to pin this on the boat builder.  Cummins signs off on these boat/motor/running gear combos, there would be no warranty without it.  There have also been cases where Cummins changes the target fuel curve for a motor as time goes on (thereby making existing boats ‘over propped’).  Truth be told your numbers are amazingly close, much more so than the average ‘old’ boat.

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Turgid Sturgeon

[JimmyK]

Start with checking to make sure the stop solenoid linkage is still hooked up.  If it is then move to the wiring.

Better yet, call the mechanic up and tell him the same story you told us.  He’ll probably know immediately what the cause is.  Likely a simple fix, and definitely nothing to do with how the valves were adjusted or TDC etc.

[JimmyK]

I have installed many of these, they are great regulators.  Install is very straightforward.  The ignition wire is just as the name implies, a +12v wire that is switched with the ignition.  It is basically the on/off for the regulator.

I have to ask though…why are you doing this?  Lots of reasons to add an external regulator but you didn’t mention any of them in your post.

[JimmyK]

The problem isn’t that 210° is too hot, it’s that it is a lagging indicator, and by the time the sensor gets to 210° and you react, there are other parts of the engine that are much much hotter than 210°.

That is the beauty of the seawater flow sensor.  It is a leading indicator.  The seawater sensor recognizes the lack of cooling water flow before anything starts overheating.

With that said, the seawater pump on these engines are gear driven, and the seawater flow sensor will not help at all when the belt goes AWOL.

I use a seawater flow alarm as well as a custom circuit that monitors the alternator.  Both are leading vs. lagging indicators and sound as soon as the root cause occurs, before the engine temp even starts to rise.

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hifirush

[JimmyK]

not a big deal but the current setup makes no sense to me, liked it much better the other way FWIW

1 user thanked author for this post.

Brad Arrington

[JimmyK]

I had CPL1975 370s, some of the first made, in 1996.  One thing that I know was different is the top end cap of the aftercooler.  I assume this changed with the CPL but not sure.  Bottom line is to try to use your engine serial number when ordering parts and don’t just assume that because something is for the ‘370’ then it will fit.

[JimmyK]

I think lots of people figure that the 6B/QSB/6C/QSC motors have such great reputations in boats that, heck, the QSM must be cut from the same cloth.  Far from it, the marinization was crap, total departure from the others mentioned, and it is as tender as slow cooked veal because of it.  I don’t blame you for being disappointed, but at this point you either prop it to prevent the turbo and manifold issues, get a new boat, or live with the problems.

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Tony Athens

[JimmyK]

-Without knowing gear ratios, the rest is useless

-People fib about their boat’s performance

-What you’re reporting doesn’t sound like an engine performance issue as you are able to achieve way above rated rpm, which is good.

-As Tony mentioned, unless you have the same gears, same weight, same engines, etc., and the exact same props (diameter, number of blades, etc.–same exact make and model props), then it would not make sense to copy someone else’s pitch.

Where were you propped before you changed, what was your max rpm, and what was your speed?

[Author]

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