8V71TI's overheat

[Nonchalant1]

I'm 3 days into a 28 day cruise and both engines get up over 185 if I run at 2000 RPM. I also see a light steam or mist in the exhaust behind the boat when running. I pull back to 1700 and they stay cool (around 175) but still emit some steam or mist in the exhaust.

Sea strainers are clean.
Water pumps got new impellers 50 hours ago (I did notice some wear on the cover plates and wear plates, but left it as is).
New raw water hoses 50 hours ago.
At least 2 year old themostats.
Port heat exchanger removed and cleaned 50 hours ago.
Both engines ran fine this season until today.
These are 8V71TI's in a 1978 53MY

Could it be the shower head? If so, how do I check it and clean it?

Suggestions appreciated.

Thanks,

Doug Shuman

 

[MikeP]

Doug - except for the steam/mist, your temp description sounds pretty much like my engines. I pulled the starboard exhaust collector last winter to have some seeps repaired and, in doing so, pulled the showerheads. The inboard showerhead was completely clear; the outboatd had one bit of swarf or whatever that was partially blocking one showerhead hole. So in my case, I know it's not the showerhead.

Removing the showerhead is pretty easy. Disconnect the raw water hose connection at the showerhead(s), remove the clamp holding the head to the the turbo exhaust flange. Loosen all the hose clamps holding the showerhead to the collector. Once this is done you will have enough play in the hose to pull the showerhead to the rear and rotate it as necessary to clear the turbo flange. Then you can simply pull it out of the collector hose. Depending on how long the hose has been clamped to the showerhead, you may have to work some spray lubricant under the hose with a small screwdriver or whatever to break it loose.

There is probably no flange gasket between the SH and the turbo. There are aftermarket gaskets available for this but I don't think DD carries them. OEM does not call for a gasket. When you reinstall, you can either do it as DD says - no gasket - or use high temp permatex silicone which is copper colored. Normally, I would not suggest using this on exhaust fittings but the temp gun shows around 200 degrees at this joint, which is far below the 700 degree max temp for the copper silicone. There are exhaust sealers that can handle higher temps but they are harder to find and not necessary for THIS exhaust joint. You should replace the flange clamp with a new one.


I was thinking about cleaning the intercoolers today but I probably won't! I was going to rig up the rig as Genesis has described and plumb it so it can circulate through the entire raw water system - heat exchanger and both intercoolers at the same time but I started some other projects so that will have to wait fo some other time.

Let us know if you find any blockages.

 

[Nonchalant1]

Mike,

Yeah...it's the steam that makes me think it's the shower heads. Presuming that they're the big 8" elbow connecting the turbo and the collector, I disconnected the hose, removed all the clamps at the big hose and the turbo and I can't even make it move at all. I can stand on it and it doesn't move. I went around the big hose with a little screwdriver, but not WD40 yet. I'll try that and if that doesn't help, I'll button up and go. We're going all the way across Lake Michigan today so I didn't want to have a big problem out there.

Thanks much,

Doug

 

[Nonchalant1]

So I buttoned up and went. All the way across Lake Michigan with no problems except I had to stay at 1700 RPM. The port engine appears to be the one steaming a little. I put my hand on the exhaust collectors and the port is a little warmer than the sb, but both are not uncomfortable to the touch.

Mike - let me know if you find out what cures yours. I'll try the PHOSPHO cleaner when I get back in a few weeks.

Doug

PS - Stabilizers are great. We had 3 to 4 ft. waves straight abeam all day and almost no rolling at all. I turned them off once and what a difference!

 

[Genesis]

The trick with those hoses is to use a flat-blade screwdirver and some 409 (yes, the cleaner)

Insert screwdriver, spray in a bit of 409. Work it around, repeat until you have it broken loose.

Rubber (including sythetic EPDM, which most hose of this kind is) will bond to the metal over time......

As for the overheat, first thing to check is the SUCTION side of the pump. Check ALL the hose clamps; every hose must be double-clamped, and TIGHT. Airleaks are murder on pumping performance.

If you know the raw water path is clean, that and the shower heads are what's left.

 

[Nonchalant1]

Karl,

Do you think the steam is an indicator of low raw water volume in the exhaust? Ergo, the shower heads if everything else seems to be OK on the raw water side? My ski boat steams every time the raw water inlet grate gets plugged. I clean the sticks out, it runs great again.

Doug

 

[Nonchalant1]

Mike,

Boat's in the barn now and I took out all 4 intercoolers and found impeller pieces and crud that got past the sea strainers stuck in the intake side of all of them. It's absolutely the problem. Low raw water flow was fine until I ran the engines longer at higher RPMs. It was also fine in the colder water of Lake Huron, at any RPMs. I'm taking the intercoolers to a good radiator shop here. BTW - the DD service manual says that 8V71TIs built prior to serial # 8VA358502 had smaller intercooler tubes that tend to block up more easily (mine happen to be made after that and they were still partially blocked with crud).

It's actually not that hard to take off your intercoolers. The flex hoses don't get stuck on that tight because DD intercooler hoses are very flexible fabric. Just take off 4 bolts from the bottom and loosen 5 hoses and it pulls out (then cover the open engine and turbo pipes with saran wrap). It takes a while to take the exchanger halves off the intercooler once you have it on your bench because there are 40 bolts and old hardened gaskets. Maybe it'd be worth it if you haven't had yours cleaned. I never had mine off and I expect the impeller pieces were from multiple prior owners since every impeller I ever took out was complete.

I have come to believe in two givens in mechanics but this only fit number one:
1. "Finding the problem is always harder than finding the solution"
2. "Nothing is ever simple"

Doug Shuman

Doug - except for the steam/mist, your temp description sounds pretty much like my engines. I pulled the starboard exhaust collector last winter to have some seeps repaired and, in doing so, pulled the showerheads. The inboard showerhead was completely clear; the outboatd had one bit of swarf or whatever that was partially blocking one showerhead hole. So in my case, I know it's not the showerhead.

Removing the showerhead is pretty easy. Disconnect the raw water hose connection at the showerhead(s), remove the clamp holding the head to the the turbo exhaust flange. Loosen all the hose clamps holding the showerhead to the collector. Once this is done you will have enough play in the hose to pull the showerhead to the rear and rotate it as necessary to clear the turbo flange. Then you can simply pull it out of the collector hose. Depending on how long the hose has been clamped to the showerhead, you may have to work some spray lubricant under the hose with a small screwdriver or whatever to break it loose.

There is probably no flange gasket between the SH and the turbo. There are aftermarket gaskets available for this but I don't think DD carries them. OEM does not call for a gasket. When you reinstall, you can either do it as DD says - no gasket - or use high temp permatex silicone which is copper colored. Normally, I would not suggest using this on exhaust fittings but the temp gun shows around 200 degrees at this joint, which is far below the 700 degree max temp for the copper silicone. There are exhaust sealers that can handle higher temps but they are harder to find and not necessary for THIS exhaust joint. You should replace the flange clamp with a new one.


I was thinking about cleaning the intercoolers today but I probably won't! I was going to rig up the rig as Genesis has described and plumb it so it can circulate through the entire raw water system - heat exchanger and both intercoolers at the same time but I started some other projects so that will have to wait fo some other time.

Let us know if you find any blockages.

 

[Genesis]

Funny how that works ain't it?

And the next thing upstream from your sea strainer is ALWAYS the "auxiliary sea strainer". Bet on having to clean that regularly - and perhaps the next thing beyond THAT!

I've learned that Detroits are very intolerant of raw water flow problems.... they have marginal heat exchangers to start with, and it doesn't take much to totally gunk them up and cause overheating.

 

[Tom Ipock]

One more thing to remember is that you are pumping some very cold water into your engine - that could have something to do with the steaming also.
Tom

 

[REBrueckner]

A neat trick to help isolate any cooling system problem is to check each engine during operating conditions with an infrared thermometer. You'll be able to detect different temps between your two engines and help identify which component is at the higher temperature. Start at the salt water intakes and gradually move thru all the salt water portion, then the fresh water...or whatever order suits your pleasure....

 

[MikeP]

Doug -nice post. I plan to pull the coolers this winter; it will be the first time I have done so (we bought the boat about a year ago). I'll be interested to see if there is any junk such as you found. The engines have around 500 hours since the previous owner had them rebuilt. I pull/replace the impellors every season and when I pulled them last year they were fine and all in one piece. Therefore, since they looked OK and the engines were redone not that long ago, I have ASSUMED that there would be no mechanical junk obstructing the cooler flow. Of course, as we all know, this assumption could be totally wrong! But it is obvious that the coolers had been removed when the engs were rebuilt so it seems a reasonable ASSUMPTION. I will post what I find when I pull them.

There has been some posts re incoming raw water deitrus clogging things in the engine plumbing but I don't see how that can be much of a problem - each RW seacock has a mesh strainer with very small holes. I don't see how anything could get in to the RW system that wouldn't just continue right on out the exhaust. But again, I may be wrong about that. We'll see.

 

[Passages]

There has been some posts re incoming raw water deitrus clogging things in the engine plumbing but I don't see how that can be much of a problem - each RW seacock has a mesh strainer with very small holes. I don't see how anything could get in to the RW system that wouldn't just continue right on out the exhaust. But again, I may be wrong about that. We'll see.

Most the junk I found in my raw water system did not come from the outside but actually grew from the RW system - broken zincs & impeller pieces plus a good quantity of accumulated scale. Base on my findings, I believe the entire RW cooling system should be removed & inspected every couple of years (3-5?) with annual treatments of the Genesis Phosphoric Acid flush.

 

[REBrueckner]

What is the "shower head" ? Is this where the salt water from the engine enters the exhaust system, just before exhaust hoses, via concentric openings around the exterior of each exhaust line??

 

[MikeP]

Yep!

On the 8V71TI it's a more-or less 90 degree large diameter pipe that connects directly to the Turbocharger exhaust out and then to the large exhaust hose which connects to the collector. It also (of course) has a raw water fitting.

 

[Nonchalant1]

Doug -nice post. I plan to pull the coolers this winter; it will be the first time I have done so (we bought the boat about a year ago). I'll be interested to see if there is any junk such as you found. The engines have around 500 hours since the previous owner had them rebuilt. I pull/replace the impellors every season and when I pulled them last year they were fine and all in one piece. Therefore, since they looked OK and the engines were redone not that long ago, I have ASSUMED that there would be no mechanical junk obstructing the cooler flow. Of course, as we all know, this assumption could be totally wrong! But it is obvious that the coolers had been removed when the engs were rebuilt so it seems a reasonable ASSUMPTION. I will post what I find when I pull them.

There has been some posts re incoming raw water deitrus clogging things in the engine plumbing but I don't see how that can be much of a problem - each RW seacock has a mesh strainer with very small holes. I don't see how anything could get in to the RW system that wouldn't just continue right on out the exhaust. But again, I may be wrong about that. We'll see.

Mike,

Me too, but it was a bad assumption on my part. My engines were majored 50 hours before I bought the boat 3 years ago and I have the Detroit Diesel receipts, but they didn't do all the things on Karl's "complete rebuild list" by a long shot. It's clear that these impeller pieces were already in the intercoolers before they were majored. They put new correct DD hoses on the turbo and water intercooler lines, but never cleaned the intercoolers and left the old center connection pipe hoses because they never took the intercoolers apart.

Also, re: sea strainers - the kind of stuff that I backwashed out can get to the intercoolers every time you clean the sea strainers. I'm always careful to not get the strained crud in the clean area, but I always see some floating around after I remove the screen, so it must be able to make it to the intercoolers. The intercoolers have very small passages, just slightly larger than the sea strainers, so they'll still gunk up with little leaf and stick particles. I marked each intercooler by notching them by position because all 4 are the same case, just turned around to make it fit differently. I also marked IN on each inlet pipe so I'd know which way to backflush them.

Doug Shuman