Boat continues to overheat - HELP

S

sotaman

New Member
Mar 9, 2009
44
Pompano Beach, FL
Boat Info
1996 Sea Ray Sundancer
Engines
7.4 EFI Bravo 3
I own a 1996 27' Sundancer with a 7.4 MercCruiser, Bravo 3. When I fisrt purchased the boat through a private sale the overheating alarm was going off everytime I ran at 3000 RPM. I had the outdrive serviced, replaced the impeller, water pump, elbows, maifold & risers. I also had the fuel pump rebuilt. For a while, it ran hot (185 degrees), but the alarm did not go off. Now it is hitting 200 degrees and the alarm is going off again. I am not sure what to look at next?? Someone suggested I take out the thermostat and see how it runs? Can the engine itself be carroded inside preventing the flow of cooling water? One mechanic said there is a hose that carries the water from the outdrive to the engine which could be clogged. Any help would be appreciated.
 
If you replaced everything you mentioned, the only two items I can think of are the hose from the outdrive through the transom that gets severely closed off and possibly a clogged heat exchanger (you never mentioned if you had a closed or open system).

Search on this board as I seem to recall a thread where someone posted a picture of the hose that got totally clogged on the B3.

Doug
 
Have you checked the power steering cooler for obstruction ? You cooling water goes through it...just a thought as it's a pretty easy thing to check. Mine is down low port side of motor with a clamp on hose on each end.
 
I too remember the post mentioned by douglee25, but a quick search did not yield that particular thread.

Anyway below is some replacement info on the intake hose, (that I believe had gotten kinked), in that thread. Not to mislead anyone, the info is pasted from one of my favorite websites... http://www.outdriveshop.com/

The Bravo's water hose is locked in place with an internal plastic retainer.
Removal requires a special Tappered Insert Tool.
Put your Tappered Insert Tool onto the end of your 3/8" rachett extension and remove the plastic tappered insert. Push the water hose through and towards the front. NOTE: It's a good idea to replace the water hose at this point.
You will need to hop up into the boat with a 7/16" socket wrench and a slotted screwdriver. Located the main intake water hose on the inner transom plate.
Remove the clamp and pull the hose off of the hose connector assembly.
Now use your 7/16" socket and remove the two bolts that hold the connector in place. You will now be able to see (or feel) the very front end of the water hose and the retainer. Use your handy Tappered Insert Tool and remove the plastic insert.
Now you can remove the hose from the outside.
 
I replaced my intake hose last spring. The engineering of the tapered inserts is another cruel joke on boaters. Accessing the insert on the inside of the boat for removal and replacement was a freakin PIA. The insert tool did not fit the insert very well. It is certainly doable but just do not expect it to be a one hour job.
 
There are two temperature sensors: 1st is wired to the alarm, second to the dashboard temperature gauge. You can also verify engine temps with an infrared thermometer (about $80 from sears). But it sounds like you have a true overheat problem.

Usually, I have heard checking/replacing the thermostat is the FIRST repair step. Not the last :) Cheap and easy on a 5.7 :)

Yeah, a kinked inlet hose is also a culprit.

Did you say you replaced BOTH the raw water pump and the water pickup pump?

I had a funky overheat problem: Turned out I was sucking air into the water pickup. This was verified by replacing the water hoses with clear plastic tubing and watching the air bubbles go through at high rpm. (the mechanics did this on the water. . .they wouldn't let me aboard to watch! -> You don't want to leave these hoses in place longer than it takes to check things out.). The cure was tearing down the outdrive and putting it back together. It was said that a $0.02 plastic screw was replaced in the process. Ran fine after that.

Build up of silt/rust scale in the CW passages resulting in chronic overheating is the classic sign for a repower in my neck of the woods. . .but that type of damage takes YEARS to produce. I don't think it would happen quick. Unless you run the engine in fine sand. . ..

Did I suggest checking the $25 thermostat yet?
 
Thanks for the help. I had a mechanic work on the boat when I 1st got it and he said he replaced the thermostat. This was a fresh water boat for about 4 years before being shipped to Florida, so I would think interior corrosion would be less likely to happen. I have been in sand once or twice since I have owned the boat, nothing major. I am going to have a mechanic relpace the seawater intake hose and see if that solves the problem, unfortunatly if it does not, I may in for a repower or I could sell the boat and get another one with outboards :(
 
Yes. . .getting a mechanic with a clue is an important ingredient to keeping older motors running.

My mechanic became stumped regarding my overheat problem. He finally brought over a buddy to help figure out the problem. (the buddy turned out to be another marine mechanic with a few more grey hairs. . .). I read about the clear plastic tubing trick on this forum; and the other mechanic was also familiar with that troubleshooting procedure.
 
I spoke with the Sea Ray dealer who was a total snob! He would not just replace the seawater intake hose. He would only do the job if I had the entire transom assembly replace with new ($2500 parts only) and said the job would take 20 hours of labor. He clearly did not want to help with the problem. I have the boat going into a reputable marina. The mechanic there said it should be a 4-6 hour job and replacing the transom assembly is a worse case scenario. I guess unless I am purchasing a boat from the dealer, they don't want to lift a finger to help.
 
Hi,

If you have a Bravo III it is highly likely that it is blocked with aluminium corrosion squashing the plastic sleeve through transom. I had the same problem and re-routed the water supply through the bottom of the hull with a quarter turn valve and strainer and blanked off the inlet before it enters the pump. You should cut out roughly 2 or 3 inches of rubber pipe from where it leaves the gear box at the back of the transom to allow cooling water to flow through. I can't recommend this highly enough, I haven't had any overheating problems since! Hope this helps.
 
I would convert this to a regular through hull with an engine mounted water pump.must more efficient and you'll never have to worry about the hose from the drive again.Also easier in most applications to service the raw water pump.just my suggestion
 
replace your thermostat! its an easy job, when is the last time you replaced it? ezed
 
ED, The T stat has been replaced.

Sotaman, Dont give up on this just yet. You've spent too much time, money & headache, to give up now. I like comsnark's first post. Can you get your hands on a temp gun to verify actual temps? I'd be pissed if those sensors are bad.
 
I'm fighting this issue right now and have done all the above(thermo/cooler/raw pump) EXCEPT check the through transom plastic part and replace the manifolds.

My 94 7.4 raw water BIII will do 1k at 160ish all day long...run the rpm's up to planing speed and she iwll hit 200 within 30 seconds.

I'm considering robbing my AC intake which has a strainer and clam shell on the outside and see if that stops the over heat.

I keep thinking it is the manifolds.They are old but flow water.They say idle over heat is impeller but higher rpms is manifolds/risers/elbows.
 
Well my trouble appears to be the transom hose.I pulled the hose and put my house hose on and let her run for 5 minutes.The risers where barely warm.No way no how could you touch them more than a tap before.I'm sure they will get warmer when I put the thermostat back in(i pulled it to rule it out).

I'm leaning towards doping the thru-hull vs. fixin the crappy hose design.
I'm a little concerned about what to do with my drive hose and it's natural cooling from the water passing through.
 
I had exactly the same symptoms a couple of years ago. After chasing the problem for about 2 months, it turned out to be in the transom hose. The actual tapered insert had collapsed. I couldn't even get a screwdriver into the remaining hole!
 
Just got word from my mechanic that there was a plastic bag and other debris causing an obstruction in the power steering cooler, I have not had a chance to run the boat to test it myself, but he says he did and it ran at 175 degrees. My hats off to Quint4 for his diagnosis. BTW, I did speak to my mechanic about all the posts from this site concerning my overheating problem. I think it helped him do some thorough checking BEFORE doing anything major.
 
How does a plastic bag end up in the power steering cooler? The drive itself has a screen on it that prevents large debris from getting in the cooling system. Something doesn't add up.

Doug
 
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