Engine help

[Liquid Asset]

Well, now that I am back from my Bahamas trip, I have some issues to address.

Since this is the most miles we have put on the boat since we purchased her, we found some problems taht we did not know we had and some issues that I address, but appearantly not good enough.

I found that I have a small exhaust leak. I can not see it, but I know that it is there because it has finally discolored the exhaust blanket. So I have to pull those, now I need to clean the turbos and fix the leak wherever is is coming from on the riser. I also have to pull my intercooler and clean that, plus the other crap involved in having an exhaust leak. Had I been closer to home, I would not have even run the boat, but given the situation I had to come home to fix the problem. Any suggestions in cleaning up after an exhaust leak would be suggested.

The real problem I do not know how to addres is my cooling system. My engines have always run around 185-187. I know that the detroit manual says taht with 180degree thermostats it is common to see 197 degrees and that it is ok, but everone has always said that not to run them over 185 to 190. I can not figure out why, I am going ot pull the thermostats and see what they are since I have never had them out. I think t hey may need to be 170 degree thermostats. Can I run withouth thermostats in a Detroit? the manual says no, but thats not always correct. Detroits manual says that 200 degrees is ok and not to run them over 210.

I feel as if the engines are just running to hot and I want to get the temperature down. Any suggestions?

 

[Nonchalant1]

Pat,

What engines do you have? 71 series are dry liner engines and 92 series are wet liner engines. That makes a big difference because wet liner engines can cook the O rings for the cylinders, but dry liner engines don't have that problem and can run a little hotter.

Doug

 

[Liquid Asset]

sorry, they are 8v92ti's

 

[CapetaniosG]

I had a similar problem exhaust leak on one of my 8v71 TI engines but mine was at the elbow of the exhaust manifold. It was a hole bout 3/8" in diameter. I replaced the manifold.

With respect to the overheating problem you're having, never run the DD's above 190 F or a couple of degrees higher for any period of time. These engines are very sensitive to high temps. and you can destroy your engines if you do.

I would start with the raw water cooling system. Check the condition of your strainer. Is it clean? If not clean it. Remove the cover of your raw water pump and check the impeller. Pull it out. if the blades show a permanent deformation replace the impeller. Check the wear plates for excessive wear. Replace if necessary. Prior to pulling the impeller out all the way notice the way the blades are bend, so when you replace the impeller the blades should have the same bend. It goes without saying that if pieces are missing from the blades, change the impellers. You may find those impeller pieces later on downstream in the heat exhanger, intercooler or in one of the other coolers.

Check the raw water strainer to make sure full flow of raw water is flowing thru. If not, barnacles may obstruct the flow.

You now move to the fresh waters side of the system. Put one hand on the inlet pipe of the heat exchanger and the other hand on the outlet pipe of the HE. you should feel the differnce in temperature. If not your HE needs a good cleaning. An IR heat gun can make your life much easier.

If you have Intercoolers they are next on the list to check. They are normally cool while the engine is running because raw water and air are going thru. But if the flow of water is obstructed by debris it would cause the engines to overheat. The same will be true with the other coolers such as fuel, gear and oil cooler. You have to check all those to make sure they are clean.

If the engine oil is low add oil to the engine to bring it up to full mark.
Check you props to make sure you don't have some rope rapped around them. Check the coolant in the expansion tank. Add coolant if needed.

Whatever you do don't run DDs without thermostats. They don't like it.
If you suspect the thermostats, remove and test them. The DD manual tells you how. You should know that the number of degrees normally semped on the thermostat is the temperature at which it is designed to open and after it opens it controls the engine temperature. They are normally designed to open at about 165F. If the thermostats are removed it will be a good idea to replace the seals and put them in the right way. DD has a tool that will make it easy to install the seals the right way.

You also may want to check the shower heads. If they are obstructed by debris that will cause overheating as well.

If you do all of the above and you still have a problem, the problem is internal to the engine and you will need a professional. Good luck. Let us know how you make out.

CapetaniosG

Hatteras 53MY

 

[Liquid Asset]

I believe there is something that is obstructed. My intercoolers and Heat exchangers were cleaned last July (I will do it again myself). But I am betting it is not that. I have a feeling that it is the thermostats because I have good raw water flow out of the exhaust. But it is possible that there is a cooler problem too. The funny part of this is that both engines normally run at 185 together and do not very much from each other, but my port engine will creep up to 187/188 somtimes. I can back it off 25 rpm's and it will cool back down to 185. I am going to pull apart the system and see what is up. I just replaced the coolant to try to help this problem, but it didn't do much. The other maintance is good. I keep them full of oil and there are not expansion tanks on my engines. Just drains into the overflow sump.

 

[Genesis]

I'll go through the entire Detroit overheating thing here for you...

First, the thermostats are FULL OPEN at 185F. Beyond that you have NO MARGIN - between 170 and 185F the thermostats are partially open and as such they are regulating the temperature. You must run in this range - beyond it you're flirting with disaster and its 30 seconds or less away if it happens.

Your alarms should be set at 195F. NO HIGHER. If you don't know what your thermal switches are set at for overheat and you can't read the markings on the switch (or you don't have markings) then remove and replace them with 195F switches. This is CRITICALLY important.

Detroits will crack heads at 205F - even momentarily. You don't want that to happen as a cylinder head is a $2,000 proposition, and that's if you catch it before it hoses one or more holes, at which point the price goes up exponentially.

Ok, now on to what's going on.

In order (most likely to least), check:

0. Pull the rear cover and check the impeller. If any question at all, pull the impeller. Use the proper Jabsco tool so you don't destroy either the impeller or the pump body doing it (no, two screwdrivers does not constitute the proper tool.) If there are blade(s) or pieces of blade(s) missing, FIND THEM - they are in the system somewhere! That gets fun! Also inspect the strainers and, if questionable, dive the boat and check the raw water intakes.

1. Raw water flow. Put suction and pressure gauges on your system. If your gear cooler is on the suction side (before the water pump) as many Covington engines are, then you need to instrument both the intake and outlet side of that cooler with vacuum gauges. Any reading over 7" HG is bad news. Note that these gear coolers often collect crud and cause problems; they should be removed to clean them (take to radiator shop) if there's a problem there. This must be checked UNDER WAY.

2. Put PRESSURE gauges on the inlet and outlet of the primary H/E (use the zinc plugs and insert pipe adapters to hose barbs, then attach gauges. Pressure on the OUTLET side of the H/E (heading towards the showerhead) MUST NOT exceed 10psi. Normal is LOWER - in the 4-5psi range at full RPM. This can be checked at the dock. If its HIGH check the showerhead for obstruction. Note that this is a royal pain to get to.....

3. Check CAREFULLY for air leaks on the suction side. The strainers are a particular trouble area - make darn sure you're not leaking air into the system. Air leaks destroy water pumping capacity. If you see salt deposits around the strainer gaskets, assume they're leaking, tear them down and fix it. Also check the intake pipes - this is trickier but at minimum check the clamps on the intake side hoses going to the pump. These will often not leak water even when they leak quite a bit of air.

4. The primary H/E can be dirty. You can pull the inlet and outlet hoses and get a quick look, but to really know you have to pull the end plates. If it looks dirty down the pipes, its not good. This can be fixed "on engine" using the flushing procedure I've posted here, you can remove the core (requires draining the cooling system) and do it in a bucket using Ph-Ospho (available at Home Depot) or you can take the core to a radiator shop and they can do it there.

5. Note that the FRESH WATER side of the H/E can be fouled with silicate deposits. This doesn't happen often but if it does happen to you it can be hard to detect. The only fix is an ultrasonic or alkali wash at a radiator shop - this one you can't fix on your own.

6. The FRESH WATER PUMP can be bad. Not usually a problem, but it can happen. If the engines have been overhauled within the last 5 years or so they should have the newer design pump on them which flows much more water than the old.

7. The thermostats can be bad. RARE but it happens. If you remove the housings you should change not only the gaskets but ALSO the seals in the top on which the thermostat poppets ride Those are kinda fun to change as they're pressed into blind hole.

If you get past #4 and still haven't found it holler here before you further, there are other diagnostics I can give you that will help before you tear into 5-7.

 

[MikeP]

At 1700RPM, my port engine (8V71TIs) consistently ran at 194-195 for (according to the previous owner's logbook) since the middle 1990's. Starboard held around 185. You couldn't run at WOT for more than a minute or two without the temps going dangerously high. At 1500, both engines would hold around 175.

I had already pulled/checked the showerheads last season and found no obstructions worth talking about - there was a small nut (as in nut and bolt) obstructing one hole in one showerhead but that was it - previous poor mechanical work, obviously. It looked like it had been there for a long time.

Over the winter I pulled the HEs and intercoolers and immersed them in Muriatic/Oxalic acid (couldn't find the Ospho locally) per DDs recommendation. I reinstalled them. I then added DDs "In Line" cooling system flush. A month later, after running the boat at the slip up to normal op temp many times during that month) I flushed that and refilled the cooling system with DD's "Power Cool" 50/50 w/water. Note that the 50/50 is needed to ensure freeze protection. You wouldn't need that level of protection in FL but you would have to add the appropriate DD additive package if you don't use the 50/50 mix.

Over the past weekend we ran at WOT for 10 minutes and the temps on both engines - per mechanical gauges in the engine rooms - held 180/182 for the entire time. At 1500 RPM both engines now hold 164.

So - It's obvious that as Karl has frequently pointed out, these engines operate with a cooling system that is, at best, only marginally able to keep up when in perfect condition. The key is getting/keeping them that way.

I'm confident that if you follow the guidance that Karl provided in this post, and assuming there are no defective components, your temps will drop to comfortable levels.

Good Luck!

 

[Genesis]

Yeah, you have to realize that Detroit originally delivered these engines with about 2/3rds of the horsepower than the marinizers eventually produced! That is, the 500SHP Covingtons that I had were originally delivered as 350s, etc.

This is a problem, because Covington did not change the H/E tanks - and while there was a LOT of margin at 300HP, there ain't much capacity left at 500!

 

[Liquid Asset]

Assuming that my heat exchangers were cleaned correctly on the raw water side last august, and that my coolant change to water including flushing the cooling system did not make much of a temperature difference, then it makes sense to me that it is most likely in the raw water side.

But knowing that the previous owner of my boat did nothing to it since he purchased it and it came out of Hatteras NC then is it possible that it had 180 thermostats. Plus if this was the case, then would it not run at 185 or above because this is where the thermostats open. These engines have run at 185 since we purchased the boat and it seems to me that if they were 170, then the engines would run closer to 170 durring the winter when the water is colder. But they ran at 185 or close to it. Please explain this a little more so that I can see if this is where I should start. In my reading of the Detroit service manual, it says that there were 170 and 180 degree thermostats produced. So if somone before me screwed up and put in a hotter thermostat, then I think the fact this boat will never see water under 70 degrees makes me want to verify they are correct.

What is involved in taking the shower head apart. Mine are not to bad to get to, but since I have never done it, I want to make sure I am not going to screw something up. It just looks like the water outlet hose goes to a 90 bronze elbow which is screwed into the exhaust. Please elaborate before I start.

 

[CapetaniosG]

To get to the shower head loosen the clamps that hold the rubber hose to the elbow and the straight part of the exhaust and slide the hose down along the straight part to free the elbow. The elbow is conected to the turbo with bolts or a V-clam. Disconnect the elbow from the turbo. The shower head is at the downstream end of the elbow. Put your hand in and feel for any debris. I cleaned mine with a high presure washer. You can actually see the shower holes from the outside. They should be free and clear. I'm assuming your set up is simmilar to mine which is an 8V71TI set up. Good Luck.

CapetaniosG

 

[dlbryan]

I am really new to mechanical of the Detroit 8v71 pls I’ll take all the ridicule with pictures, where are the impellers and pls talk to me like a 4th grader and should I just do like always and call a mechanic. I’m really trying to learn to do some of the basics.

thanks

 

[racclarkson@gmail.com]

I am really new to mechanical of the Detroit 8v71 pls I’ll take all the ridicule with pictures, where are the impellers and pls talk to me like a 4th grader and should I just do like always and call a mechanic. I’m really trying to learn to do some of the basics.

thanks

An honest man for a change. Welcome! It's one of the easy ones.

The crayon was your idea.

 

[ageless]

oops--my bad

 

[rustybucket]

My engines have always run around 185-187. I know that the detroit manual says taht with 180degree thermostats it is common to see 197 degrees and that it is ok, but everone has always said that not to run them over 185 to 190. I can not figure out why, I am going ot pull the thermostats and see what they are since I have never had them out. I think t hey may need to be 170 degree thermostats. Can I run withouth thermostats in a Detroit? the manual says no, but thats not always correct. Detroits manual says that 200 degrees is ok and not to run them over 210.

I feel as if the engines are just running to hot and I want to get the temperature down. Any suggestions?

I'm confused (or dumb lol). Few questions:

1. What temp are your engines currently running at? @ What RPM?
---- if you have temp readings at different rpm's it can often help pinpoint where the issue is.

2. How are you taking temp? Dash gauges? IR? Digital temp sensor?

I installed a digital temp sensor and we see 185-186 at cruise (1850rpm's). At WOT it creeps up, but we are still overproppped so I'm pretty sure that is the source of overloading so we don't stay at WOT long.

I know everyone is pointing you to engine/cooler components, and rightfully so. But the first question I would ask is what is your WOT rpm when loaded for your bahama's trip?


My last comment, running the engines cold, is almost as bad as running them on the high side of the temp window. I would NOT put cooler thermostats in unless there was a damn good reason, and running at 186deg is not a good reason to put in a lower temp thermostat. Running colder does NOT increase engine life. The engines were designed to run at a certain temp, in a perfect world they run that same temp all the time. But... at idle our cooling systems are WAAAYY overkill and at WOT they are just robust enough to do the job.

 

[racclarkson@gmail.com]

Guys, GUYS!! It’s a 13 year old overheating issue post.

 

[rustybucket]

Guys, GUYS!! It’s a 13 year old overheating issue post.

Bwhahahahaha. who raised this from the dead??