Losing coolant and making oil!

[Sonic Boom]

Sonic Boom performed more like Silent Boom yesterday. While idling out the temp gauge started to creep. At 200 degrees (mechanical gauge showed 185) we shut down and idled back to the shed on one engine. Found the heat exchanger empty, refilled and started the engine. Upon startup noticed excessive blow by for idle, then the temp started to creep again. Rechecked the oil and it was 1-2 inches above the full mark and the heat exchanger was already low.

Originally thought it could be an oil cooler till we saw the blow by. Is there any common items that could be causing this? Cracked head maybe? Anyone know any test to isolate the coolant leak without pulling the engine apart?

Probably thinking too far ahead here, however, is it worth rebuilding a 33 year old 671TI engine that's inefficient and 1,000 pounds heavier than a modern powerplant (we just installed new turbos and rebuilt the intercoolers)? Not looking forward to spending 70-80k for a repower. We love the boat and it's a tank (for it's size) but not looking to make emotional decisions either. If it turns out to need a new engine do we cut our losses and dump it?

Sorry for the random thoughts and thanks in advance for any advice you can offer! Greg

 

[Pascal]

Tough one... a boat with a blown engine isn't worth much so you ll have to do the math

Repower only make sense if you re going to keep the boat for a while and if you use it a lot. I m about to pull the 8V71Ns and install factory reman c series cummins, hopefully in August. Even without having to upsize the shafts it's goign to be $100k by the time they re in ($76k for the engines and gears) but in my case it's worth it

First thing to do is do the math between boat value, repower cost and condition / hours of the other engine and of course find out where the problem is. Cracked head, gasket etc.

 

[Sonic Boom]

Your spot on Pascal!

The other reason I hate to give up on this boat is per Sam's, only 20 were ever made in the express version. Even fewer were Hurley's....

Any way to check if it's a cracked head without removing it?

 

[Boatsb]

Making oil as in fuel contamination or water?

The Detroit's are pretty rebuildable but if it's worth it to you I just quoted a customer 550 hp cummins 6.7 with gears. New not reman at $108k including everything from the fuel filter to the exhaust elbow.

The would be a great boat for those engines.

 

[SeaEric]

Fix the engine. It is by far the most cost effective solution.

 

[jim rosenthal]

I agree with Eric. You might call T&S Marine Engines in Crisfield, MD- although not many watermen still use Detroits, those guys grew up on DDs and are very experienced with them. Or you can go to Western Branch diesel, who are DD dealers, but it will cost you a lot more.

You might have a cracked head or blown head gasket. That doesn't require pulling the engine, I wouldn't think, and the rest of the engine may be fine. If you can replace the broken parts and get her going again, it is the best choice for the least money. If you like the way the boat performs, repair it and continue to enjoy it.

I understand that it's not going to be cheap, but it IS the cheapest of the alternatives, and you already own this boat and love it, so it seems the thing to do is get a diagnosis and get it repaired.

 

[SEVEN]

How many hours on the motor? Did it just over heat all of a sudden or has there been something leading up to this?

 

[Sonic Boom]

it's losing coolant and mixing with the oil, the fuel part of the equation seems fine. As for performance, it's a 21 knot boat at 2050 RPM. Not a runner by today's standards but were content with it all things considered. In a perfect world would love to have 6CTA Cummins mechanicals in her.

Hour meter shows 1500, however, guessing it's closer to 2500 (SWAG). We purchased it from the original owner who never fished it so don't think it's been run very hard (only four rod holders on the boat).

As for engine history, this was the first time we've seen it run hot. We were idling out of the creek when it happened, never got above idle since it idles at five knots. The only precursor to this event was excessive blow by last time out. Checked on the engines and saw a little smoke, thought it was a small exhaust leak at first. Wasn't bad enough to idle back in though, whatever the problem it happened quickly.

Thanks for all the advice gentlemen, going to refill and pressure check the heat exchanger and try to locate the leak...will keep you posted

 

[SEVEN]

Happening that fast should not be a cracked head. (in my opinion) make sure you check the impeller once you find this issue. Keep us in the loop.

 

[bobk]

On my 6V92 TA, a coolant leak into the oil led to an in-frame rebuild.. Glycol is said to be bad on bearings. I run a lot and wanted reliability and it was covered under my insurance policy.

Bobk

 

[SEVEN]

Good call on the insurance company. I would've not thought something like that would be covered.

 

[Sonic Boom]

Would be shocked if insurance covered this one.

Dad and I refilled and pressure checked the heat exchanger this afternoon. When doing so heard a gurgling noise around the oil cooler. Hoping for the best and expecting the worst, we pulled the air box cover next to it on the number one cylinder looking for coolant. Looked much better than expected and was dry. With this said were hoping the oil cooler is the only problem and we did not crack a head. Could the extra oil/coolant mix in the sump cause excessive blow by due to the crank churning it? In hind site it seems the blow by progressed as the oil level rose? Or the crack in the head is growing....

 

[Boatsb]

Is there coolant in the oil?

If so you need to get it out and rinse out the engine before the glycol damages things in there

 

[mykim]

Sonic Boom performed more like Silent Boom yesterday. While idling out the temp gauge started to creep. At 200 degrees (mechanical gauge showed 185) we shut down and idled back to the shed on one engine. Found the heat exchanger empty, refilled and started the engine. Upon startup noticed excessive blow by for idle, then the temp started to creep again. Rechecked the oil and it was 1-2 inches above the full mark and the heat exchanger was already low.

Originally thought it could be an oil cooler till we saw the blow by. Is there any common items that could be causing this? Cracked head maybe? Anyone know any test to isolate the coolant leak without pulling the engine apart?

Probably thinking too far ahead here, however, is it worth rebuilding a 33 year old 671TI engine that's inefficient and 1,000 pounds heavier than a modern powerplant (we just installed new turbos and rebuilt the intercoolers)? Not looking forward to spending 70-80k for a repower. We love the boat and it's a tank (for it's size) but not looking to make emotional decisions either. If it turns out to need a new engine do we cut our losses and dump it?

Sorry for the random thoughts and thanks in advance for any advice you can offer! Greg

6-71 is a heck of a good motor. Hell of a lot cheaper to rebuild vs replace. But if money is not an issue then put in new ones.

 

[BOATER BOB]

You can pick up a 6-71 pretty cheap on Ebay
Bob

 

[Sonic Boom]

Following up so hopefully we can save someone else a few headaches down the road....

Turned out to be the freshwater pump. When the engine warmed up and had pressure on the heat exchanger, the water pump bearing and seal were allowing coolant to pass and dumping into the blower drive hence getting into the oil pan. Going back together next week when the pumps arrive and check for subsequent damage.

Thanks for all the advice gentlemen!

 

[kelpy]

That can't be right. The water side and the oil side of the circulating pump don't use a common seal.

 

[SEVEN]

Once it's back together let us k ow if that was really the fix. Sometimes there are multiple issues.

 

[rsmith]

That can't be right. The water side and the oil side of the circulating pump don't use a common seal.

X2 unless the weep hole was plugged

 

[kelpy]

Could have been. Routine visual inspection should have caught that if, in fact, that was the case. I have never found one plugged though.