Please Help: 7 Years of Buzzer Issues on 1996 Yamaha's 150's

[Doc of the Bay]

I have a buzzer issue on both my 1996 Yamaha 150's Saltwater Series but they never buzz at the same time. The buzzer usually goes off anywhere from 3200 RPM on up. My temp gauges are between the first and second mark on the gauges so it's not showing hot. After a few minutes at idle the buzzers quit buzzing. If I run below say 3200, I hardly ever have a buzzer. The red water temp is blinking on the Yamaha gauge when the buzzer goes off. So, today I took off in the bay and at about 4000 RPM's the port buzzer went off. I checked the temp. on the heads with a infrared heat gun right next to the sensors (the ones that just pop into the holes on top of the heads) while the buzzer was still going off. One side was 138* and the other was 126*. I put the continuity tester on both sensors and the light lit up and then went out of course when the buzzer stopped. My temp gauges stayed between the first and second notch. Both engines have been buzzing on and off for over 7 or more years. I have changed thermostats, poppet valves, heat sensors on both motors, water pumps, had the heads removed and water jackets cleaned and recently flushed the engines. First thought would be the wrong sensors (too low of a temp setting) or defective sensors. But, this buzzer issue was occuring way back 7 years ago before I installed 4 new sensors (2 per engine). One day I got so pissed at the problem that I popped all four sensors off of the heads and ran at 4800 RPM's for a long period of time with the temp gauges staying right below the first notch on the gauges, no overheating !! PLEASE HELP !!! Thanks in advance, Doc Buzzed Out on the South Louisiana Coast.

[Doc of the Bay]

Anybody??

[CentralTexas]

I’m wrestling with a similar issue, only sets an alarm at 4k and up. Water pump changed and thermostats checked. I haven’t checked the sensors or the PRV. When I pulled the Thermostat covers there was a lot of calcium and lime buildup and I think that’s my problem. The boats been run mostly in fresh water in Texas and our water has lots of mineral deposits in it.

From what I’ve read, this buildup was blocking the heat transfer from the heads to the water (It’s a great insulator). The water temp itself was fine but the head was running hot. In your case your temp gauge probably has a sensor right in the water jacket. The Yamaha gauge sensors are reading the temperature of the metal, that would be why your water gauge reads OK and the Alarm is going off. This condition can also result in hot spots which could also explain the good head reading you got and why the problem didn’t resolve itself when you changed sensors. It would also mean you are running hot.

Most of what I have written here is what I’ve read on the subject. No first had experience, but I’m about to get it. Hope this helps.

[CentralTexas]

Since posting the above I notice you’ve had the heads pulled and both the water jacket and heads cleaned. Did you do this yourself? For my prior post to be valid it couldn’t have been done well. I don’t think a regular flush would help if it is a deposit issue. I tried picking some off my thermostat housing and it’s like cement.

[Doc of the Bay]

Central Texas, thanks for the reply. I had a Yamaha mechanic shop pull the heads and dip them in acid and then blast them clean. I also flushed my motors a few weeks ago with a vinegar / water solution then reflushed with plain water right after. I am beginning to think that my thermo sensors are setting off too early. With the temps I mentioned above shown on my temp laser gun right when the buzzers went off, the sensors are definitely closing way too early. I am going to pull them and test them in boiling water with the temp gun, continuity tester and an ohm meter. I don't know where else to turn. Let me know if you find out any more useful info and I will do the same. Thanks, Doc of the Bay

[CentralTexas]

Doc – I think you are right and should check the temp sensors at this point. The cleaning and flushing procedure you described should have fixed any buildup issue. I can see why you’re really frustrated. The cooling system on these outboards is not really that complex and it seems like you’ve pretty much addressed everything. I hope one or two of the temp sensors checks bad. If they are all good I don’t see how it could be anything but hot spot issues since the head temp checks good with an infrared gun and the internal water temp is good based on your gauge. Since you say both motors do this, I was going to ask if you are sure you’ve got good water flow over the water pickups at higher speeds but I’d think your water temp gauge should read high if that’s the case.

I’ll let you know how my problem turns out but it’ll be a couple of weeks before I get through the buildup removal part. Good luck to you.

[BQUICK]

I've seen some mechanics put a blob of high temp grease on the sensors to make them less sensitive. Doesn't seem like the right way to go about it but it does seem to work......

Another thought is that they are running lean which will cause the heads to spike in heat but not show on the water temp gauges.

[Doc of the Bay]

CentralTex, I thought I had bad water flow at high speeds also or maybe some cavitation from a transducer. So I removed all transducers and disconnected the trim tab pistons and hung the trim plates out of the water. Still had buzzer issues. Then, I lowered both motors about 2 inches and this lined up the cavitation plates with the bottom of the hull, still buzzer issues. BQuick, I never thought of using a high temp grease to make them less sensative. Yes, it doesn't sound like the right direction to go in, but, after checking my sensors this weekend, who knows , I am so desperate I may give it a try. Thanks guys, Doc of the Bay

[BQUICK]

Might want to install some water PRESSURE gauges to see if that shows anything going on.....

[Doc of the Bay]

I have water pressure gauges BQuick and they show normal pressure. thanks, Doc

[CentralTexas]

Doc – I thought of something that might help you troubleshoot this further. You could do this if your sensors test good or beforehand. They make a thermomelt stick that looks like chalk when applied and melts at a specified temperature. My repair manual says to use a 163 degree stick to test if it’s running hot. I have a 1989 115 and I don’t know if your 1996 150’s are different. The instructions are simple; apply a liberal amount in a line on the surfaces you want to check. I’d do the top, bottom and both sides of each head. I’d also put a couple of lines on the head cover. Don’t apply it close to the spark plugs since that area will run hot. Getting a good temperature of the head when your alarm sounds is tough since only the edge is exposed; the head cover covers the main portion. You also have a time delay, and a drop in RPM, between the alarm sounding and getting back to the engine to test it. After this you should know if the heads are getting hot anywhere.

[Doc of the Bay]

Central, I never heard a thermo melt stick. Sounds like something to check out. I tested my thermo switches on my two 1996 Yamaha 150's in boiling water on the stove with a continuity tester and my infrared heat gun. Listed are the four switches and their close and open temps. I tested each one three times and the readings were all within a couple of degrees. Looks like I have a sensor issue with all 4 or I have the wrong switches. Correct me if I am wrong. I really appreciate all the help. The Yamaha diagnostic chart shows the switches should close at 183*-194*F and should open at 140*-165*F. Doc



Close Temp-Light On Open Temp-Lt.Off



Thermo Switch #1 152* 89*



Thermo Switch #2 156* 91*



Thermo Switch #3 155* 92*



Thermo Switch #4 163* 94*

[CentralTexas]

Unbelievable! I own a wholesale auto parts Distribution Company in Central Texas and all I can say is that’s one run of defective parts. I think you have your answer. I know I don’t need to say this but I can't help it, order 4 new ones, reconfirm the specs and check before you install them. Make the dealer get it right.

Good job following your gut.

[Doc of the Bay]

Central, yep, this has to be the problem. It is possible that the four thermo switches were mis packaged and the wrong sensors were under the correct #. I have seen that many times when I was in the autoparts business. Wholesale auto parts? I was a store manager for AutoZone for seven years and then a store manager for Oreilly for six years. Small world. Thanks again , Doc

[CentralTexas]

You’re welcome, but I don’t think I did anything. It is a small world isn’t it. I’m in Automatic Transmission Parts distribution. Our customers are AAmco, Cottman, etc. Probably explains why we both turn wrenches.

Give us an update once you install the new sensors.