Constant overheating alarm

C

CaptMac

New member
It's been awhile since I've made a post but being that there are many C-ory owners with carburated 90 hp Honda outboards (mine is a 2000, 90 hp with 1,400 well-maintained hours). The problem is my overheating alarm keeps coming on. I can get about 20 minutes if I keep the speed under 15kts, but if I go to 18-20kts, the alarm/rev limiter will come on every 4-5 minutes. I take the motor to the honda dealer every year for a full tune up incl a water pump new impeller, thermostat, oil, filter, lower foot lube and fittings greased. In fact, I just took it back to the honda dealer for this problem, of course it wouldn't come on while at the doctors office, but they put in a new water pump, impeller and thermostat but it sounded the overheating alarm/rev limiter the very next day. Someone suggested there may be a bad "sensor" what and where ever that may be. Does anyone have any suggestions or similar issues? Thanks.
 
I would also have the water passages checked for corrosion/salt build up. Some folks us "Salt away" to help remove deposits on a routine basis. I had a similar problem on a Yamaha, and we had to have the passages cleaned. This seems to be more of a problem in our Florida waters, where both the water temp and ambient temperature is high.
 
At this point, I'd be grabbing my infra-red thermometer and finding out if this engine is really overheating. Simply pointing and measuring points around the engine should confirm or deny any hot spots.
 
I thought Wild Blue /Capt Jim at one time had his motor a 135 Honda flushed with muriatic acid. He runs in salt water a lot down at the tip of Texas where the water is real warm. I think you get a build up and the acid gets rid of the build up. I have been wrong Send him a P.M. he is good people.
D.D.
 
The muriatic acid flush is how it is done. Some times there needs to be mechanical removal also. I got my IR thermometer at Radio Shack, but Sears, Home Depot etc all have them--and they are essentials in every tool kit.
 
My alarm went off a few years ago, but only when I was idling. Turned out to be a partially stuck thermostat. As I recall it was pretty inexpensive to fix. Might be worth a try before doing anything else that's more expensive.
 
CaptMac,

I have a 2004 75 HP Carbeurated Honda with approx. 700 well maintained hours and have been dealing with the same issue for the last 2 years! Very frustrating! When it first happened, I went through the entire list of fixes. Replaced the water pump impeller and thermostat first...no help. Bought an infrared thermometer at Harbor Freight for about $20 and ran the boat with the engine cover off while I sat back by the engine. When it overheated, I shot various places on the engine and it had indeed overheated. I replaced the heat sensor anyway which did not make a difference. Next, I replaced the relief valve and the flush valve which had really a lot of salt build up as I had not been using that port to flush the engine. Also replaced all the spark plugs...no help. Next, I thought that there must be a leak in the valve cover gasket that was letting heat into the water jacket, but that wasn't the problem either. At that stage, I took it to our local Honda dealer and they took the engine apart, acid washed the inside of the water jacket and then put it back together with an all new gasket set. That was the ticket....for awhile! I have used Salt Away after every use since then, but it seems as though the salt glazing is building up again and the problem is returning. I really don't know where to turn at this stage. I was wondering if there is some way to add muriatic acid to the regular flushing method of using the water muff and then also flushing through the flush valve. Maybe Dr. Bob can tell us if there is a way to get the acid into the flush water without having to spend $1800 to have the engine taken apart. Would it also be a good idea to contact Honda Marine and see if they have a fix for this problem? Looking for any help I can get.

Ever Hopeful...Tad
 
Question for Dr. Bob,

How can muriatic acid be added to the flush water when using a muff type unit to flush the engine while running? I just started using the muff to add Salt Away by attaching the Salt Away dispensing unit between the muff and the water hose. I do this in addition to attaching the unit to the rear non-running flush port and flushing with S.A. after I have flushed the engine while running...trying to get the S.A. into the water jacket from both directions. Do you think that the acid would damage the Salt Away dispenser or the rubber seal of the unit? Again, any help is greatly appreciated.

Thanks...Tad
 
I wanted to follow up on the issue of my engine overheating. I bought a new thermostat and gasket for the 2004 Honda BF75A. While talking to the parts man, he told me about a company in Jupiter, FL that makes several boat products. The company is Woody Wax and they make several products for exterior finishes like soap, wax, metal treatments and also an engine flush. I contacted the company about the flush product and they kindly sent me a sample of the flush product to try. Their flush is different from SaltAway in that it has a petroleum content to it and supposedly leaves a lubricating film on the inside of the water jacket and also lubricates the impeller and thermostat. I was very excited and flushed the engine twice last week for a Saturday test run. To my great disappointment, the engine overheat alarm came on after only 1 mile which just happens to be across from my house on Merritt Island. I drove the boat over to my dock, pulled the cowling off and removed the thermostat completely while installing a new gasket. Took the boat back out to the channel and test drove it for 10 miles at 5000 + rpms and it ran cool as a cucumber @ 25 + mph.
My question to the group is: Should I leave the thermostat out which seems to let the engine run below the overheating temperature or am I doing some long term damage to the engine by running it without the t-stat? My SELOC Repair manual says: "The purpose of the thermostat is to prevent cooling water from reaching the powerhead until it has warmed sufficiently for optimal performance with minimal emissions." Our water temperature on the ICW here in Florida where we run the boat mostly, is in the mid 80's for the late Spring, Summer and most of the Fall, so the engines get warmed up pretty quickly.

I appreciate any help...Tad
 
Tad, if the engine runs cool enough (without the thermostat) that the alarm does not come on, it sounds like your thermostat is "too hot". I.E. it doesn't open fully at a low enough temp. Since your engine is way out of warranty (congratulations on 1400 hours.. :wink: ), personally I'd leave it out (or go find a thermostat that opens fully at a lower temp). I'd let it warm up alongside before getting underway for 5 minutes or so and enjoy the silence (without the alarm) and the higher speeds! :thup

Charlie
 
I would remove the thermostat and place the t-stat in a pan of water and heat the water up with a thermometer to the temp that the thermostat is rated to open and see what is the scoop. Maybe the T-stat was in the motor upside down. I sorry already for saying that but it would certainly explain it not opening. It happens in the best of families. Make sure nothing in the way like gaskets or corrosion build up interferes with the t-stat opening. The engine is designed to run in a temperature range. Running it at cooler temps might make it not as efficient and in some cases is responsible for a build up of unburned gas that migrates into the oil causing the engine to appear to be making oil as the gas is added to the crank case. Not good good for the long term life of the engine imho.
D.D.
 
I have had a similar problem with my twin honda 40's. I have had the boat for 2 yrs now. There has always been a very annoying intermittent buzz, only a second or so. These buzzes can be seconds or many hours apart. No warning lights come on. I did have a overheating issue with a damaged impeller last year and this has lead me (falsely) to suspect the temperature sensor. Both motors have new impellers, and run at the same temperature as checked with an inferred heat gun. Suspecting a faulty temp sensor, I disconnected both temp sensors and the buzz continued. It also continues with the oil pressure sensors disconnected. There is warning buzzer on the tilt control, to prevent you running the motor with the water intake raised out of the water. I have not yet tried disconnecting this system yet. It seems as thought it has to be done at the buzzer in the motor control. It's the Y/G wire to the buzzer. The temp and oil have a different wire connection to the buzzer. I have read of people complaining of trouble with the tilt alarm on Hondas. I think its a glitch they haven't worked out yet. They also need a light along with the buzzer. With twins you can't tell which motor is sounding.
I'm convinced the motors are running fine. The buzzers really annoy me. I have to take out the seat to get to the controls and haven't done it yet, but I think the tilt alarms are the culprit!
Does anyone have any experience with tilt alarm problems?

Bruce Cassal
"Carpy"
 
Charlie,
I believe you have it right! Had a chance to work on the overheating problem again this past weekend. We left on Thursday for a long weekend down in Ft. Pierce. I got nervous before our trip and bought a NEW t-stat for the Honda 75. Put it in after I had flushed with SaltAway and with the Woody Wax flush. I thought with all that treatment and a new t-stat, I might have fixed the overheating. Left the dock at 6:30 and headed toward F.P. Only made it 2 miles before the overheat alarm went off! Immediately pulled off the channel and over to one of the spoil islands...pulled off the cowling and removed the t-stat completely. Took back off toward F.P. which is about 75 miles south. Ran the whole way except for manatee zones at 4500 or better rpm's at about 20-22 mph. Absolutely great. No overheating or hesitation at start off speeds. Cold starts (such as they are here in FL) were not a problem at all. Just let the engine heat up for about 10 minutes before we started out in the morning and throttled up smoothly. Water temperature was 83 degrees for most of the weekend. I don't know if I am doing any long term damage by running without the t-stat, but it is the first time for a year or more that we were able to run at that speed without waiting for the alarm. Even Toby said it was so much nicer cruising at higher speeds because we took on opposing wakes, chop and passing wakes so much smoother and easier. Should be interesting to see how the engine warm up is when the water temps are in the 60's during our Christmas trip on the St. John's River.

Tad
 
Tad you should see if you can get a different t-stat that will open at a lower temp as others stated. If you go to a body of water with a far lower temp I would think that you would have problems with the motor reaching a temp that would allow for complete fuel burn. When I moved here for california with my old 2 stroke I could not get it to idle for trolling. I shorted the oil in the fuel just a little so the motor would warn up enough to burn the fuel oil mix better and not foul up the plugs. I could have also got with a hotter t-stat as well.
 
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