another warm engine

[jim rosenthal]

Tony, my engines have about 700 hrs on them, I think. They were in a CAT dealer boat that belonged to Alban engine- this was a demo boat- then taken out, majored, and sold to me. The major was a complete disassembly and all new replaceable internals (rings, bearings etc). So essentially they have about 300 hrs on them SMOH.
I talked to the CAT folks this morning and they suggested a lower range thermostat, a 165, which they are sending. We'll see if that helps. I hope so, I am running out of things to do to fix this.

[garyd]

Overheating can make you crazy. If possible I would make a set of hoses that would allow to swap the port and starboard pickups. Therefore the port pickup feeds starboard engine etc.

I once had a intake that developed a salt ring on the inside. It was from the boat bobing up and down in the slip and then the water evaporated leaving a salt deposit, must of took years. However it did the same thing as you discribed everything I did helped a little. But when I found that, and removed it, that fixed it. I actually got very lucky to find it.

If you swap hoses, you could even swap after the raw water pumps, you would know a lot more than you did before the swap. Having twins can make trouble shooting easy if you swap stuff side to side.

have fun boating garyd

[farauscher]

>If you swap hoses, you could even swap after the raw water pumps, you would know a lot more than you did before the swap. Having twins can make trouble shooting easy if you swap stuff side to side.

Garyd has good points with switching the intakes, but be careful swapping after the raw water pumps. You have to be sure to match the engine speeds so your water flow rate is balanced.

Fred

[jim rosenthal]

After cleaning the heat exchanger, replacing the raw water pump impeller, having a diver check the seawater intakes, and checking the engine with an IR thermometer.......I replaced the thermostat. That's what the problem was. It runs fine now, at the temp that it should. So....at 400 hrs or thereabouts, both thermostats have failed, fortunately sticking in the partly-open position. This in spite of changing the coolant every 2 years and using CAT's additives. So...I'll change them preventatively when I change the coolant. They only cost ten bucks or so and it will be worth the peace of mind.

[jim rosenthal]

A postscript to the above...after I thought I had the problem solved, it came back: too much engine temp on the port engine at higher speeds, say over 2100 revs. Back to the drawing board...called the CAT guys in Crisfield and they felt that running hot at high revs probably meant a worn-out seawater pump. So...they sent me a new seawater pump, which I installed.
Sea trial: done Monday. Because of weather I couldn't get up to full speed (it looked fine in the creek but when I got out in the Bay it was running 2-3ft), so the best I could do was 2400 revs, but she stayed cool at that speed and I THINK the problem is solved. I am having the old pump rebuilt and will put it on the other engine. Then I will rebuild that engine's pump for a spare. And move on to the next challenge.

[divert00]

79 43C with 6v92TA, 450hp, 2100 origianal hours. Could not get port engine to stay cool at high rpm. Over last 12 months, changed/cleaned everything from intake to h/e to shower head including raw water pump impellor and cover plate. All helped, but did not resolve completely; settled for cruising @ 1900 rpm. Raw water pump began leaking (looked original), so I sprung for a new one: CASE SOLVED. I am guessing wear had increased internal clearances and reduced suction efficiency at high water velocities.

Did I mention how reasonably priced the Jabsco pumps are? NOT. I hope they all last 25 years.

[jim rosenthal]

No kidding. Sherwood pumps (what CAT uses) are no cheaper. I guess this goes in the list of "replace before it give trouble" items. What is annoying is that I did not have many hours on this pump, if the pump was indeed the problem. The good news is that they are meant to be rebuilt- ie, meant to wear out, but be rebuilt- so I can do the remaining two for less.
I recall reading about Gilkes gear pumps which are supposed to be far more durable- they advertise in B&H. I don't know if they are available for CATs and if they are actually any better. They are even more expensive than Jabsco or Sherwood pumps.

[ADaily3224]

Jim,

Thanks for advise. I have 365 hours, and the temps never go over 180, I must have 180 thermostats. I wonder if they should be changed to 165? I also put the Cat, straight from the bottle permanent red antifreeze in last year. I put new impellers in 165 hours ago. Just trying to avoid problems.

I went to the Annapolis Boat show, wondered if your boat was close to the show. I guess I'll be running an old used Hat for a while, the prices are off the charts.

Tony D

[34Hatt]

Jim I was putting in new Impeller's in my buddy's boat Cat 3116's with 400 hr's when I pulll the port side I saw the shaft wave to me it was shot. So I got him a new pump since it was the end of June and we were leaving in a week for a 15 day cruise. Your right not cheap I read on Boat Diesel that they suggest to carry a spare. So to the question I have is old one to be rebuilt are you doing it yourself or sending it out? This winter I am putting the cummins 330b's in and guess what they have the same pump!!!!! :-{

[jim rosenthal]

They DO have the same pump. Tony Athens at Seaboard Marine has mentioned that the inner wear plate on this model Sherwood can get loose and chew through the back side of the pump chamber, if I have it right. For that Sherwood took him off the distributor list...nice guys. I am having T&S Marine rebuild the pump I took off the port engine, which I will put on the stbd engine- that one is NOT running warm but I am not going to wait at this point. I will rebuild the stbd engine's takeoff pump- Tony has rebuild parts that are supposed to be better than Sherwood's for this series pump. That way, I'll have two new pumps, plus a rebuilt one, and I will have learned how to do it. I'll carry the rebuilt one as a spare. Note also that when you change the pump, you have to have new O-rings for the pump spigots- the pump does not come with the fittings that bolt onto the pump and receive the hoses from the seawater supply and go up to the heat exchanger. You have to move those from the old pump to the new one, and the seal is made by rubber O-rings. My engines have return fuel coolers, which also make the seawater supply hose very short and get in the way.
I don't know that running the lower thermostat makes much difference. I am going to leave the other one alone. I am not sure that a 15 degree difference in water jacket temp will affect performance. It will be interesting to see. What I DID learn in this whjole episode (and I think G posted something on this a while back) is that the pump can look pretty good, and you can put in a new impeller, and it will still not pump enough water to take all the waste heat away from the engine. Evidently there is not much reserve built into these systems.
On the Boatdiesel forum there has been a running discussion of the performance envelope in which modern high-speed lightweight marine diesels operate. These engines run at rather high internal stress levels- lots of boost, high performance demands, heavy boats loaded with a lot of luxury items, and rather aggressive propping that loads them heavily. And now this on top of all that- a cooling system that is only adequate when it is new and doesn't have much reserve capacity built in. My pump had possibly 500 hours on it, at the most. I watch engine temps very carefully now, and I don't think any damage was done, but it's just one more instance in which I think of these engines as high-maintenance items- high-strung thoroughbreds, if you will, that will give a lot of power and performance, but have to be closely watched. Not like the naturally-aspirated diesels of yesterday, which would run forever at their low specific power outputs.
If I were repowering this boat again, I would use Cummins C series engines, which weigh about the same as 3116s, but have more displacement. For those engines to produce 350-385 hp, they don't work nearly as hard. I would feel safer with those engines because they would be operating at a lower point on their power curve than the 3116s do. The cubic capacity is dramatically different- 3116s are 403 cubic inches, C series are 506. So, 25% bigger.
If you look at some other makes of marine diesels, they have redundancy built into the cooling systems which gives you a reserve cooling capacity for when you are operating the boat in very warm seawater etc etc. I think Luggers have that, for example. I'm not going to try to reengineer the system, obviously- I'll just carry another pump and spare impellers, and keep everything as clean as I can- but in the unlikely event I have to ever repower another boat, I will scrutinize these issues much more closely. Live and learn, as they say