'06/'07 Yamaha 70hp. Strange Alarms

dbkimbro68

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May 23, 2016
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I just picked up a '06/'07 70hp Yamaha motor that was originally a pontoon boat engine and installed it on my FULLY Restored '83 AlumaCraft Bandit. Installed a New 703 Remote control unit, NEW,o.e.m. waterpump impeller, New,NGK sparkplugs, cleaned the carbs(Sat up 2 seasons), have the tach/trim gauge with only oil warning indicators, volt gauge, and clock. I ran a pre run/SeaFoam de-carbon/cleaning test with foot in a constant full water tank to be sure that the cooling system was working correctly, and not knowing about the oiling system, I ran it on pre-mix. The oil tank was half full of red Yamaha oil,and I marked the tank at oil level to see if the level dropped after running(oiler works).. Motor ran GREAT for 2hrs in tank from 30min at idle,30min at 1800rpm(fwd),30min at 2800rpm,30 min at 5000rpm then back to idle for the last 30min... Motor performed PERFECTLY with no alarms. I removed and cleaned the oil level switch/strainer,filled the tank to 1/2" from top of the tank, filled up the 12gl fuel cell with non-ethanol 93 octane and for peace of mind,added 16oz of Quicksilver 2cycle oil to fuel along with another16oz bottle of SeaFoam. Headed out to the lake,ran the boat for several hours(5-6) to see how it performed on a 17ft aluminum bass boat at no wake speed, trolling speed,all the way up to a 5900rpm max rev speed... Motor ran GREAT,,, of a top speed of 37mph and used only 6gl of fuel and about 1.5in drop of the oil level in on motor tank... No problems,no alarms.
2 days later I filled the fuel tank and set out for a day of fishing on the lake. Motor cranked fine,ran fine for about half a mile at 5900rpm and then BAM!! the alarm goes off,motor boggs to 2100rpm and ran like $H!T.. Had a perfect flow of warm water coming out of the "**** tube", could hold my hand on top of the cyl head(2-3min), oil level full,arrow on tach gauge pointing to green full indicator... Shut motor off, trolling motored about .25 mile to a sandbar island and tied up. Sat there waiting,going over everything I could think of that may have been causing the alarm and found NOTHING... After an hour of waiting,checking every 5minutes via key turn for the alarm to go off, I re-cranked the motor(no alarm), checked the water output flow and temp(perfect) and started back to the truck. Motor ran GREAT again at 5500rpm back to the dock. Tied the boat to the dock and left it at idle while backing the trailer in and had my friend at the boat waiting for an alarm. Motor was at idle maybe 10-15min,and no alarms. As I started to load the boat onto the trailer, the alarm triggered again as soon as I revved up to 4250rpm for the final "push" onto the trailer and I shut it down.
When I got it home,I put the foot back into the water tank,cranked the motor and let it run.. Water temp and flow from the "**** tube" was perfect and laserd at 165?f..but after about10min at idle,the alarm goes off again. I again went to checking things that relate to triggering an alarm, and found NOTHING that should be causing this.. After sitting for 24hrs, I took it back out, ran it for a bit at 4500rpm and it did ok,then as I,went to full(5900)throttle, the boat planed out,went 200yrs and acted like it was starving for fuel,then picked back up,ran a second then acted as if it was loading up,then starving again. I came back to idle,pulled the cooling and revved it at the carbs a couple of times... Revved up good but was a little oil rich,but it,seemed understandable since I have a low mix pre-mix fuel along with a working oiler system.
I put the cowling back on,but it in fwd and started back up to speed... Ran great,no starving/loading, no alarms, and did fine.....until I got to exactly 5600rpm and the alarm goes off again.
I am VERY well versed in automotive mechanics and repair, but have very little experience with2 stroke outboards... I have been through every single thing that I can think of,every troubleshoot that Yamaha has in the owners/service manual that pertains to the alarm going off,and I am at a COMPLETE loss..
Has anyone else had anything close to, or these symptoms happen to you? and if so,what was the final determination of the cause and what was the repair???

Please help in any way possible... I don't have anymore hair to pull out of my shaved head!! ,LOL!!
 

99yam40

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Test the over temp alarm and the oil level to make sure they operate as they should.

If the gauges do not indicate what is happening then you will have to eliminate the ones you know about when it is happening.
Disconnect the pink wire from over heat switch while the alarm is in to see if that is causing it.

Could be at high RPMs there is a hot spot by the switch do to plugged cooling passage

some motors have under voltage and water in fuel alarms, but I have no idea if your does
 

dbkimbro68

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May 23, 2016
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I have gone through the oiling system and cleaned it thoroughly,replaced all of the oil lines. I have replaced the thermostat with a factory Yamaha part,along with the waterpump impeller. Cleaned and flushed the water passages and tank tested the system for water flow(ok).. I have found that when the alarm goes off,i can unhook the red wire from the (I'm guessing)the temp sensor,and the alarm stops sounding. When it's running,either at low rpm or at speed,i t will start acting as if it is starting to bogg,or starve for fuel and just loose all engine speed and die. I can,let it sit for a few minutes and crank to,and it seems to have a dead skip for a few seconds,then it will rev,go into gear and run ok again for another few minutes before doing it again. If I plug the red wire back up,ran alarm will be going off and it won't rev over 2g... I am at a loss as to what else could be causing these problems.. I can't afford 100hrs to take it into the Yamaha shop,and I'm already so far over budget on this,that I will never be able to get my money back out of it. I know it has to be something simple,probably not cheap,that's the root of all of these problems, but I can't,for the love of god,figure out what it could be.
I'm not sure if the temp sensor is faulty and causing this,or what... I know it can't be overheating when I crank it cold and within 5minutes at idle,or 30minutes at speed the alarm goes off... I'm ready to drop this motor off the back of the boat and we've to it as it sinks to the lake floor...
I wish there was a temperature gauge connected to the motor, but all I have it a digital tach/trim gauge with the oil level(red,yellow and green). I've had enough, and at a loss as to what else to check.
Please help...if possible... Thanks
 

99yam40

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So is the gauge indicating it is an overheat or anything at all?

not sure where you are disconnection a red wire as I thought it was pink on the over temp,
but I do not know what motor you have or what color wires it has

if it is over heat, do a web search for Rydlyme marine descaler . have read people have had good results flushing their out boards with it to clean out cooling passages
 
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dbkimbro68

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May 23, 2016
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The tach gauge has a 2 digit readout,ie: 20 ?100, a trim indicator and at the bottom it has a red(empty/low),yellow(half level) and green(full) square box with a arrow indicator. I don't have the voltage gauge or clock connected as of yet,due to trying to figure out why I keep getting an alarm. This motor is a pontoon boat motor,and I know that the prop has a different pitch on the blades than a prop for say a bass boat,but according to the tech at the area Yamaha dealer/service center, this shouldn't make much of a difference in anything other than the overall holeshot and top speed.
The temp sensor(I'm guessing) is located on the head side of the motor,sortof between the #1 and #2 sparkplugs on the right side of the cyl head/block. It looks like a black rubber plug with 2 wires(red/pink and a black) that are about 6in long and connect to 2 wires that are under a cover right next to the O.B.C.... I'm not sure exactly what the O.B.C. actually does on this motor being that it is a carburetor motor and not fuel injection motor, but I know it has a purpose. I'm wondering if for some reason this system uses a temperature controlled fuel delivery like a E.F.I. system does, but in my knowledge of carb setups, I've never seen this.
I thought that maybe a little piece of the old impeller rubber may have gotten into a water passage and restricted the water flow,but I have back flushed the motor with pressurized water and have not seen any pieces of rubber come out into the catchpan. Trying to figure this out has been a total fiasco,and I am at my wits end. This is a 10pin harness motor,and as I said, I purchased a N.I.B. 703 Remote Control unit,so that there was no way I would make a mistake in connecting the motor. I did have to make a 2 wire harness to connect the oil level switch to the tach/trim gauge, but everything else was direct plug in.
It's starting to really get on my nerves.. A new waterline,new thermostat,new plumbing on the oiling system, new NGK plugs,new fuel tank,new fuel hoses,new fuel filter between the tank and prime bulb,new prime bulb,cleaned the motor mounted fuel filter and cleaned the carbs... The only thing I have left that I can think of is replacing the water temp sensor/switch... It has become a nightmare that I can't wake up from.. I can't understand what could be causing this problem, or understand why it will do perfectly fine at times, but more times than not,it acts up and turns a peaceful day/night on the water fishing into a $#!tstorm of alarms and running like hell.
I wish that I had never bought a Yamaha 2stroke,but the price was hard to pass up.
 

99yam40

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never heard of a Yamaha gauge that did not have an indicator for over temp only oil level.
can you post a pic of the gauge

are you sure about that?

What is OBC?

if disconnecting the pink wire stops the alarm, then either the switch is bad or there is a hot spot it is seeing due to a plugged cooling passage where the switch is located.
simple enough to pull and test the switch in a pot of water as you heat it up to see what temp it closes and opens up
 

dbkimbro68

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May 23, 2016
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On board computer.... I've tried to post a picture, But it says it is above 2.010mg.
Let me see if I can resize it.
 

dbkimbro68

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May 23, 2016
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It won't let me resize it below 2mb.
Maybe the part number will help..
27C... The only number on it..
 

dbkimbro68

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May 23, 2016
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I'm hoping that the picture will show up when I get done. In the Yamaha70hoping off manual that I have downloaded,i t doesn't show this particular tach/trim gauge,i t shows,like you are saying,a couple different gauges and they have either a temp/overtemp indicator or light,or a temperature gauge.
I pulled the temp sensor and put it in a pan of cold(55?f) water. I connected my voltmeter pos to pink,neg to blk,set it to 2k ohms and placed 3(digital,spear type dial,and a mercury deep fryer) thermometers into the pan of water. I set the stove eye to 6 and let the water come up to temp over a 8min timespan. In watching all 3 thermometers and the voltmeter,at exactly 192?f the meter went from 1. To 0.000,i then moved the pan to a cold eye and started to add ice. As soon as the water temp dropped to 187.89?f,the meter went back to 1., so I am going to guess that the sensor is working properly.
I talked to an older man today that has fooled with 231st outboard motors for many years,and was telling him about the problems with this alarm, and he said it sounds like there may be a small piece of the rubber impeller blade that is still in the cooling system that is moving around and could be plugging a passageway close to the sensor causing the alarm. He said with the alarm tripping at different times,like within minutes after cold startup, or cold startup to 15-30minutes,that a passageway getting plugged up could be the cause.
After installing the new impeller, and lower unit, and removing the thermostat and housing,i connected my unregulated water line(75psi) to the foot intake via a slip on attachment and poured the water to it. I had water coming out the pee hole,but none at the thermostat hole until I cranked the motor. After a min or so,the water coming from the tstat hole was getting pretty warm,but the pee hole water was still cold.
 

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99yam40

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tell tail water comes from before running through the block so it should always be cool.

if the temp switch meets specs then you know there is a overheating happening at the site the switch resides

drop the lower unit and hook that water hose directly to the pipe heading up to power head, leave the stat and housing off.
turn on the water fully and let it flow, inject compressed air from time to time into the water going into the motor to see if that will dislodge something.

if that does not get it out see if you can rig up something to force water into the motor at the stat hole to see if that will get the debris out.
They make something called Rydlyme marine descaler that you can circulate through the motor to dissolve mineral build up to see if that will help

last thing you can do , pull head , power head, and other plates to see if you can see and remove what is blocking things.
 
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