I’ve had chronic overheating issues since I bought this boat. I have removed and cleaned both sides of the raw and fresh water systems, new oil coolers, rebuilt both water pumps, cleaned out the shower heads, replaced the fresh water pumps, new thermostats, both engines are actually complete inframes with less than 10 hours, every moving part except the crank and camshafts were replaced or rebuilt by me. I literally I could type for 30 minutes about everything I’ve done to chase this problem. I would like to verify I have the correct water pumps. I have 8v53’s, and my impellers are the 2.5” variety. I was talking to another guy with same engines in a hatteras and he says his are the larger pumps with the 3.5” impellers. He says the 2.5” were only supposed to be on the 4 and 653’s.

What pumps am I supposed to have ? This is one thing where the manual is unclear, it gives me a long defunct part number for the impeller but no indication of pump size. I’ve just been taking the old ones to west marine and matching them when I replace them like everybody does. Detroit water pumps are all pretty similar looking so the pictures don’t really tell me much. I will say my boat has never seemed to pump as much water as I’d expect for the size of the engines. My dad’s hatteras does that thing where the water flow actually fills up the mufflers and it goes “whoosh” and spits water 3’ back from the boat. Mine sort of trickles.

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Have you had the heat exchangers “boiled” at a radiator shop to eliminate calcification that will insulate the tubes,  causing your engines to overheat.

Chris, my 8V53'S have the 2-1/2" impellers. replaced the pumps complete last year. They were original pump  cores. I run 175 to 180 all day. 190, maybe 195 with the throttles stuck in the corner.

Heat exchangers were removed and boiled in an acid bath. I’m open to suggestions, I’m at wits end with this. If I can’t solve it I’m going to just sell the boat.

Chris,

As Jim stated the 2.5in. impeller is the correct impeller and pump. This same pump was also used on the 6V92 also so it does the the flow capacity.The 8V71 &8V92s use the 3.5in. impeller pumps.

I think you need to take a systematic approach in trying to diagnose what is going on.

First maybe we should discuss what you exactly mean by "chronic over heating issues?"

The sea water pump is rated at flowing 77GPM. The raw water system is also specified to have a maximum pressure of 10psi and the maximum intake suction is 5in. vacuum.

There are also the raw water pump seals that do go bad after a while but this problem usually shows up as a sea water pump that loses or does not want to maintain prime.

Not sure exactly how your engine is setup. Many of the 8V53 engines used the Chris-craft aluminum risers that bolted to the end of the exhaust manifolds. These risers had a flex hose that fed the some of the raw water discharge flow through the nozzle on top of the riser. These engines also had a flow control valve that had a secondary discharge that went over board through an above the water line discharge port. The purpose of the flow divider was to give a pressure bias for the flow going to the risers since the riser nozzle ia actually at a higher elevation then the hull discharge port. Sometimes the riser nozzle can get plugged and will be a source of problems.

Some installations also just used an S shaped pipe with a mixer head that bolted on the end of the exhaust manifold. Either way, each style needs to flow the 77GPM flow rate or at least very close to it.

If you are not flowing the 77GPM, the heat exchanger will not be able to transfer adequate heat to the raw water. The heat exchanger load from the engine is specified as 10,180BTU/min. Putting the sea water flow rate of 77GPM yields a 15.73 deg. F temperature rise across the heat exchanger. If the difference between the sea water temperature and the heat exchanger discharge temperature is less than 15.7 deg. F, the sea water loop is okay. If the delta T is greater than the 15.73 deg. F, then we do have a problem with the raw water loop somewhere as we are not flowing enough.

If the problem is not in the raw water loop, the next thing to check is the delta T across the heat exchanger on the fresh water loop. A delta T on the fresh water side of 11 deg. F equates to the 10,180 BTU/min. capacity if the heat exchanger.

This is where things can get confusing if we are not careful and think them through. If we have a high delta T, say something like 90 deg F, another words the hot coolant going into the heat exchanger is the indicated water temperature and the return coolant temperature to the water pump is at or close to sea water ambient, then we do not have sufficient flow through the heat exchanger on the fresh water side.

This would give us a couple of likely possibilities of what might be going on. First is we do not know exactly what thermostats are in your engines. The thermostats were available from 160F to 190F. If your chronic overheating is always running at 190F-200F, then here is a good possibility. Note I am not encouraging you just to take them out to verify. It is better to know what is exactly going on than just diving in.

The other major possibility is that all of the Detroit 53 series engines used the  same fresh water pump style. There are pump housing castings for mounting on the left or right side of the engine when viewed from the end opposite the flywheel. Normally, Detroit uses the convention of viewing the engine from the flywheel end of the engine however for the water pumps, the side convention is reversed from normal convention. To add to the confusion, there are right and left hand rotation rebuild kits for the water pumps, This refers to the direction of rotation of the impeller, not the crankshaft rotation direction. Also consider that all of the 53 series engines were configurable as rotating in either direction except for the 8V53 which only came.in the right hand version but all of the Detroit 53 series camshafts always rotate the same direction irregardless of the crankshaft direction.

So now that we are all thoroughly confused by all of this, we just need to remember that on the 8V53 the water pump rotates in the same direction as the crankshaft when viewed from the front of the engine, that is CCW. We just need to make sure that the impeller matches this direction. A backwards rotation impeller will still pump coolant, just not at the same flow rate. Not implying that that is what you have going on and I would place this problem low on the probable problem issues list but it is a problem that can occur by inexperienced counter people, mechanics, or just confusing in direction convention reference.

Before you drain your cooling system and tear things apart, I would suggest to make a temperature map of the fresh water cooling tubes first with the engine at operating temperature. This might indicate some other issues and save you the task of removing and taking the back cover off a perfectly correct coolant pump..

I'll offer you a couple hundred for the boat and take it off your hands since it is broken. :)

By chronic overheating I mean back when I got the boat if I went over +/- 1500 it would overheat very quickly. After everything I’ve done to it now I can run on plane for maybe 5-10 minutes and it slowly creeps up until it will ring the 210f alarm bells if you let it get that far (I don’t after the rebuilds). Once I see it rising I back off and the temp seems to take forever to dissipate back to normal 180 levels. Both engines behave the same way, nothing I’ve done has fixed it. It’s made it better for sure, but hasn’t fixed it. Anything over about 2200 and it starts creeping up. On my boat I need 2400-2500 to stay on plane. The engines turn 3k no load and 2800 loaded, 23x21 props. The thermostats are 170 and all 4 are new.

I don’t have the waterline raw water discharges I’ve seen some boats with, it all just dumps into the exhaust. Personally I’ve never seen a 47 commander with the split discharge setup, you know more than I do I’m sure, but I’ve just never seen one. I had the manifolds removed during the rebuilds and am told they looked fine. The exhaust system and shower heads are about 10 years old, I had them removed and inspected, and they were clean. I went through the wrong fresh water pump issue so you’re spot on in mentioning that, it was flowing backwards on the port side. Diesel pro sent me the wrong one by mistake they assumed the engines counter rotated. I replaced it with the correct rotation and again the problem got better but is still there.

Ron where are you located ? Do you know anyone in FL who you’d trust with your boat? I’m sick of this and I don’t care what it costs at this point I just want it fixed. I have had my two mechanics throwing parts at it for years and done everything personally I can think of. I will print out your post and bring it down there with me if I can find somebody to run the boat for me while I’m down there in the ER. I really need competent help on this.

This is the flow at idle to port which is the worst of the two in terms of overheating although they both do it. It’s anemic compared to every other boat on my dock with Detroit’s. My dad’s hatteras with 871’s pumps probably 2x or more as much water.

https://youtu.be/bgGPamS5_iU

https://youtu.be/bgGPamS5_iU

Chris,

Are you sure the temperature senders and gauges are working correctly? Also, get one of those infrared thermometers and look for hot spots on the motors when the alarm goes off. This can also be used to measure in / out on the heat exchanger plumbing.

Chris,

I'm located in the upper Midwest so don't know of anyone in your area.

For a sanity check, I would suggest that you take some pictures of the hoses and piping on at least one of your engines. Whatever is wrong with the one is likely wrong with both since they both behave very similarly.

I would also suggest to pull one of the zincs on the heat exchanger and put in a zero to 30 psi gauge and monitor the pressure at an idle and see how high it goes at WOT. Only need WOT for a moment to see. The sea water pump is rated at 77GPM @10psi or less at 2800 rpm. If the pressure goes above 10psi, you are going to loose flow.

Do you have any pictures of the the exhaust mixer and shower head? Particularly the number of holes and the hole size. Being that you have had this problem since you have owned the boat and that the exhaust system/ mixer was redone around 10yrs. ago, you might just have an incorrectly constructed mixer.

I am also interested in seeing how the sea water feeds into the shower head. You need around 1.24 in.^2 of total area per side to get the needed flow at the 10psi. if the orifice holes are very small, the total area needed increases.

Also would like to know some of the details in how the flow is balanced between sides on the engine exhaust.

Chris Wickersham said:

By chronic overheating I mean back when I got the boat if I went over +/- 1500 it would overheat very quickly. After everything I’ve done to it now I can run on plane for maybe 5-10 minutes and it slowly creeps up until it will ring the 210f alarm bells if you let it get that far (I don’t after the rebuilds). Once I see it rising I back off and the temp seems to take forever to dissipate back to normal 180 levels. Both engines behave the same way, nothing I’ve done has fixed it. It’s made it better for sure, but hasn’t fixed it. Anything over about 2200 and it starts creeping up. On my boat I need 2400-2500 to stay on plane. The engines turn 3k no load and 2800 loaded, 23x21 props. The thermostats are 170 and all 4 are new.

I don’t have the waterline raw water discharges I’ve seen some boats with, it all just dumps into the exhaust. Personally I’ve never seen a 47 commander with the split discharge setup, you know more than I do I’m sure, but I’ve just never seen one. I had the manifolds removed during the rebuilds and am told they looked fine. The exhaust system and shower heads are about 10 years old, I had them removed and inspected, and they were clean. I went through the wrong fresh water pump issue so you’re spot on in mentioning that, it was flowing backwards on the port side. Diesel pro sent me the wrong one by mistake they assumed the engines counter rotated. I replaced it with the correct rotation and again the problem got better but is still there.

Ron where are you located ? Do you know anyone in FL who you’d trust with your boat? I’m sick of this and I don’t care what it costs at this point I just want it fixed. I have had my two mechanics throwing parts at it for years and done everything personally I can think of. I will print out your post and bring it down there with me if I can find somebody to run the boat for me while I’m down there in the ER. I really need competent help on this.

Hi Chris,

This might be silly & I don't know very much about diesel cooling systems, but seeing both engines are doing the same thing I thought I would throw this out there. What is your coolant mixture & or have you checked it? The reason I'm asking is because I had 1 of my truck engine rebuilt a few years ago & after the rebuild engine would overheat at high RPM's? Found out that after rebuild someone put straight coolant in the engine cooling system which could not cooling engine at high RPM's, but at low RPM's it was fine? Again don't know much about diesel cooling systems. Thought I would share my story with you.

Mario

Interesting issue.  I have two things to contribute here.

1) The amidship raw water bypasses did not exist on the 1970 models however were made standard on the 1971’s.  Our friends 1969 did not have them nor did a 1970 we met in Mystic, CT.  The three of us were lined up sequentially at a marina.  

2) Has anyone said anything about installing mechanical water temperature gauges replacing your electrics.  Stewart Warner makes one that would fit quite well.

3) At the time of our 47’ “Rendezvous” with the other two, everyone noticed how the ‘69 & ‘70 sounded exactly  identical while our ‘71 sounded so differently.  Our exhaust pipe size was smaller also.

In conclusion, I think I would look at my exhaust manifolds to riser to shower head connections as well as my muffler intake and exhaust ports for good flow.

Jim Rivas

Update on this.

So I pulled the shower heads, not only clean but oversized, large holes, I can’t imagine they will ever get plugged like some do. Per Ron’s advice I put a pressure gauge on the line going to the shower head and I was getting around 2 psi. Ron said it’s supposed to be no lower than 10. The heat exchangers, oil coolers, everything have been manually removed and cleaned. So I had the pumps rebuilt again, no change. Out of ideas, I put the bigger 8v71 water pumps on there that have the 3.5” impellers instead of 2.5”. That only made like a 2 psi difference, still not what it’s supposed to be. Now I was really at wits end. I called this guy who’s been working on Detroit’s for 50 years, just to see if he could tell me what’s wrong. He looks at my engines and says where’s the pipes ? Then he measures the hoses and says they are too small. The former owner replaced all the copper piping with rubber hoses. On the bright side besides being a cheap ass at least he also made sure they were all the wrong size. The guy walked right up to the problem I’ve been missing the whole time. I feel pretty stupid.

The main feed to the heat exchanger was supposed to be 2&3/8 mine were 1.5”. The rest were all weird sizes too, smaller than required. So small that getting the hoses off the fittings was ridiculous, I had to cut them. Don’t know how PO got them on there to begin with. It all got put back together and now I have the opposite problem, see the attached pic. I’m pretty sure I could just untie the ropes and the exhaust would push me down the river like a jet ski at this point.

So here’s my question for Ron and Jim. Would you put the original pumps back on, or would you keep the additional water flow and add a side discharge to even it out like some of the later boats had ? I have a 1970, so far as I know mine didn’t come with them originally. I’m guessing this is too much water in the exhaust to run it like this ? I boat exclusively in Florida with water temps in the mid 80’s, usually the more flow the merrier.

Not the Jim you are looking for but either way you need to lessen the amount of water. There will be too much back pressure in the exhaust. The easy thing is to put the smaller pump back on. That still won't mean you'll have the correct flow/pressure. There's a reason that the bypass was added in 1971. That being said there is plenty of 8v53's without a bypass. Id start first with the smaller, correct pump and go from there.

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