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

[Doc of the Bay]

Thanks again Central. I will send a reply once I get the new switches tested and then installed. I will not know how to act turning 5200 on the tach. Doc

[Doc of the Bay]

False Alarm: Buzzer Issue NOT Fixed

After reading the posts above you would think that I solved my 7 year buzzer issue on my twin Yamaha 150's. Nope !! The infrared heat gun I used to obtain the closing temp of the thermo switches was defective. It was giving a false reading of the sensors in the water on the stove. I went and bought a digital meat thermometer and it showed all four thermo switches were good. They all closed at 190* or right above that. Well, back to squrare one! I tested the cooling temps sensors today with an ohm meter against the Yamaha specs at different temps and they were good. Went and ran the boat again today and at about 4100 RPM's I got a buzzer on the port engine and head temp was under 140*. Temp gauge showed normal temp. Then the buzzer stopped as it always does within a minute or so. I ran again up to 4200 and both engines started buzzing. The temp symbol was blinking on both my Yamaha gauges. Head temps around 140*. I checked my water pressure gauges and they are running at 12-13 @ 4000 RPM's. I am lost with this issue. Any thoughts greatly appreciated. Thanks guys, Doc of the Bay

[99yam40]

What are you using to get this 140 deg head temp?
The same gun that was giving the false readings while testing the switches?

Next step would be measuring the temp where the alarm sensors are located with a known accurate measuring device to see if it is truly getting to an over-temp situation. may have to remove sensor to take accurate reading.
May be having some kind of circulation problem and getting hot spots only at the point of sensor contact

Not sure if the alarm is set off by the switches directly or do the switches send the info to something else like CDI or ECU and that in turn sets off alarm and blinking light.

[Doc of the Bay]

99Yam, no, I bought a new digital temp gauge and took a reading in the cup where the thermo switches set. I know, if the thermo switches open above 190* on the stove, then the blocks must be overheating. To my knowledge, the sensors are set off on their own and not thru the ECU. Like previously mentioned, my temp sensors for the gauges both tested to the correct Ohms at the correct temps, so that tells me the temp gauges are reading correctly, which is always below the second notch on the gauges, even when the buzzer goes off. The needle on the gauges doesn't go up any when I get a buzzer!! Thanks, Doc

[99yam40]

Still think you need to take accurate reading somehow when alarm sounds of what the alarm sensor is actually at.
Meat thermometer may not be the best

[CentralTexas]

Hey Doc, I thought you had it nailed with the temp sensors. Back to the drawing board again.

Since you’ve already change Tstats, PRV, water pump, Temp sensor (and confirmed the ones on are good) as well as pulled the heads and cleaned out any build up that was there, I think you have to have a circulatory problem that’s effecting both engines. With everything you’ve done, the odds of having this long a lasting isolated mechanical problem in both engines is really small.

Has there ever been a time when both engines were not acting up at the same time?

[Doc of the Bay]

Hello again Central !! Yes, most of the time either one or the other engine buzzes (only overheat symbol on one gauges goes off), but like this weekend, while trying to toubleshoot the problem, both engines showed overheat symbol at the same time. As I mentioned, I checked both cooling temp sensors that send the temp reading to the gauges, and they both test to the T with the correct Ohms at the designated temps on the Yamaha test charts. I just can't understand how the thermo switches, which didn't close in the test until over 190*, would close at a lower temp on the blocks. I was told by a Yamaha dealer mechanic who is also trying to figure out my problem, that the engines must have heat spots at certian high RPM,s and may be setting off the sensors. Circulation issue is possible, but, as I have stated, I dont know what else to change! One thing I never changed on the water pumps is the seal where the pickup tube goes into the top of the plastic housing. Maybe these two seals are bad and I am losing water between the seal and the pickup tube, but, my water pressure gauges are reading 12-13 psi at 4000 RPM's. Doc

[jb123]

7 years.... same hull ?
did the 2" drop make any change ?
when you did pumps did you also replace housings ??
too bad you dont have 2 single 704s and single keys to isolate the motors

[CentralTexas]

I agree with you and think you proceed as if the engines are running hot. I’m still thinking you have a water pickup problem when running on plan. Is there any way you can run one engine at a time at 4500-5000 rpm on your boat out of plane to see if the engine still overheats, ie with the transom way down in the water? Considering what you have done already, it’d be an easy test to rule this one out.

Considering everything you’ve done, there has to be a common denominator that’s affecting both engines at the same time and always has.

[CentralTexas]

I just read jb’s response and checking your water pumps again is a good idea. If you’ve had or have water pickup problems you could have water pump damage.

[99yam40]

My thoughts are that water pickup problems due to hull design or motor mounting should show up on his water pressure gauges.
even water pump housing problems or impeller problems should show a reduced water pressure

Does anyone know what the normal water pressure should be at 4200+ RPMs?

Are these motors propped properly?
Have they ever been able to hit 5500?
But not sure that would anything to do with overheating

Has these motors ever been able to run without alarms coming on at high RPMs?


Maybe broken off internal anodes or scale build up are causing circulation problems in the block

Rodbolt17 do you have any input?

[rodbolt17]

on the engines, there is a 4 wire connector.
its white.
has an orange,pink black and gray wire.
back up a few inches and find the gray wire bullet connector.
unplug both.
that wire is the visual indicate but its spliced to the pink alarm wire.
anything that takes either the pink or the gray to ground will trigger the alarm.

[99yam40]

Rodbolt17,
Are you saying to unplug both the white 4 wire connector and the grey wire bullet connector and leave them disconnected or just while troubleshooting for something taking it to ground?
Or is it just the grey bullet connector that needs to be disconnected?

I am thinking low oil level is possibly coming in at high RPMs due to plugging oil filter but since the pink and grey are spliced together it sends the signal to gauge as overheat maybe. Just trying to understand your instructions.

[CentralTexas]

Not trying to be a wet noodle here but if you look back at Doc’s first post he describes checking the sensors with a continuity tester to confirm the sensors were triggering the alarm. He also has 2 engines with the same problem and separate overheat circuits. Anything is possible but it seems to me the probability that it’s a wiring\sensor issue is very remote. If I’m reading this correctly, he would have to have consistent and repeated faulty grounding occurring on both engines under the same high rev conditions.

99YAM40 – I agree that good water pressure readings would tend to contradict a water pickup issue. My only thought was he could still have partial water pickup with pressure but insufficient flow. I’m like you though; I have no idea what water pressure reading he should be getting or how partial pickup would impact pressure. Again, a long short, but everything in this case seems like it’s a long shot. Your internal circulatory restriction guess seems good to me but he’s had the heads pulled and the system cleaned. The restriction would have to be in a part of the engine that cannot be observed when disassembled. Plus, the same thing would have to be happening in both engines.

[99yam40]

CTex
Yes I remember he said that, he also said even at toward the last that the temp of pocket where switches sit is only reading 140 deg. So looking for something different that is giving a false temp alarm.

Seems like I remember reading about someone plugging a connector to a place it did not belong causing alarm problems, but cannot remember exactly what motor or problems

If grey wire is the visual indicate wire to gauge and it is spliced into the pink wire for oil level and over temp , then sounds like even the low oil level will turn on visual for overheat or anything else that grounds the pink or grey will