2nd opinion on yam 115 overheat

[mthomas]

1989 model 115 yamaha. motor seems to run fine until 4000 rpm or higher,alarm goes off and cuts engine to reduced rpm. Ck heads with temp gun 135 to 145 degees.let engine continue to idle and cool and when alarm goes off cotinues to run unless you go over 4000 rpm. did a search on this site and cked for loose connections ground etc. no luck take it to a local yam dealer(fresh water) and he want's to overhaul.since the compression cks above 125 on all cylinders I give him $70 and say not yet. Mech at my coast home says let him have a look. he thinks motor is in really good shape and does not need overhaul,so goes to looking for overheat cause. the thermostats have been replaced,water pump replaced, poppit cleaned and inspected.themoswitches cked ,can't find anything wrong with engine. Launches boat and overheats above 4000
Or more specifically the alrm goes off.pulls heads of and ck for water restrictions, all clean.replaces new water pump said that the other one was not oem, I reminded him that I bought the waterpump from him 3 months prior.alarms again. He now suggest the next thing to do is to pull powerhead and look for
"airleaks into or from the exhaust.?? Estimate for that another $387, I asked him to hold off and let me think about this as he alreadt has probably 700 -800 in charges to date.
I really am at a critical point here as the motor of that age is probably only worth a couple of thousand at best . I also believe that he is looking in the wrong direction as I don't believe the motor is overheating 135 -145 degrees and that the problem lies with the temp alarm in some way. Any suggestions would be greatly appreciated, sorry this is so long
Thanks
marc

 

[rodbolt]

Re: 2nd opinion on yam 115 overheat

I just hadthat issue with my 88 115, turned out to be a defective temp switc.
I found it because as soon as the hot horn sounded I popped the hood and dissconected the pink alarm wires. disconnecting the stbd side shut off the alarm and resounded it when plugged back in. a feel of the heads had told me it was not hot. switched the temp switches and the problem went to the port side. replaced the port switch and ended my issue.
its a matter of testing, if your positive its overheat and not slow oil transfer then isolate which temp switch is setting the alarm and test it. switch should close about 180*F and open at 150* or so.

 

[mthomas]

Re: 2nd opinion on yam 115 overheat

I am getting the boat back from the mech thurs. I will try some more trouble shooting on my own this wkend . I just can't see putting another 387 dollars into pulling the powehead . They are totaling my bill today and am sure around 7-800.thats enough for this age motor.bye the way they said they put good thermoswitches on it and still alarmed,then cked the oil sender and it was ok too.
I don't understand how it could be the oil sender because it only happens above 4000 rpm and laso cuts engine rpms when the alarmgoes off,
If all else fails I am considering disableing the alarm system before I have to invest anymore big bucks. I know that may be risky but with the age and value of the motor its also risky to keep feeding it money. Thats a last resort of course.
Thanks for your input I will let you know results after this nxt wkedn
marc

 

[whiteguy]

Re: 2nd opinion on yam 115 overheat

I would be intrested in the outcome as I have the same motor with the same problem and replaced the same parts with the same results, both sensors checked out as well, and motor ran great and cool for miles at wide open without sensors, then died. It turns over fine,has good comp. but has no fire to the plugs now and cdi tests 0 across all positions.
Could a cdi going bad cause the overheat/limp problem? or is it seperate and coincidental

 

[Ray Neudecker]

Re: 2nd opinion on yam 115 overheat

There should be no connection between the cdi and overheating. CDI failures are exremely rare on the V-4 and V-6 models. Lack of fire can be caused by a kill switch problem or a battery too low to spin the motor fast enough to fire.

 

[whiteguy]

Re: 2nd opinion on yam 115 overheat

There should be no connection between the cdi and overheating. CDI failures are exremely rare on the V-4 and V-6 models. Lack of fire can be caused by a kill switch problem or a battery too low to spin the motor fast enough to fire.

Thank You, I will check both ASAP, I would rather buy a new kill switch than a CDI. Then I can get back to work on the overheat alarm issue.

 

[rodbolt]

Re: 2nd opinion on yam 115 overheat

why not dissconnect the white wire from the CDI and rerun your spark test? that will isolate all the kill circuits to the CDI. beaware if the motor starts there is no way to electrically shut it off.

 

[mthomas]

Re: 2nd opinion on yam 115 overheat


alarm goes off above 4000 rpm after about a minutewith either temp sensor unplugged but not with both unplugged. mech said poppit vane and grommet looked fine would you change gommet anyway before pulling powerhead off or is there any way to ck to see if exhaust is getting in the incoming water?

 

[rodbolt]

Re: 2nd opinion on yam 115 overheat

either temp swictch can set the alarm. did ya test it as I described ?
actually I would determine wich switch was setting the alarm and verify an overheat or a switch failing.
but thats just me.'

 

[mthomas]

Re: 2nd opinion on yam 115 overheat

alarm goes off with either switch conneted but not if both are disconnected mechanic tested both switches in water and were ok switched them out for new anyway and new ones did the same

 

[mthomas]

Re: 2nd opinion on yam 115 overheat

alarm goes off with either switch is conneted but not if both are disconnected mechanic tested both switches in water and were ok switched them out for new anyway and new ones did the same,, I am puzzled why after a minute at anything above 4000 rpm the heads only check with laser thermo 135 on left bank 145 on rgt bank but temp alarms goes off
if it were voltage related would it not go off immediately at 4000 or above?

 

[rodbolt]

Re: 2nd opinion on yam 115 overheat

cause ya failed do do as I asked.
sorry I cant help any more

 

[mthomas]

Re: 2nd opinion on yam 115 overheat

If you will re-read my post you will see that I or more specifically my mechanic 225 miles away did test the switches the way you asked.in water ,heated and ck for continuity.He said they cked ok.I am just taking his word for that. He said that in addition to that he tryed new switches.same result. alarm. He pulled the wires off just as you did ,one at a time.if either switch either were connected it set the alarm off. when both were DISconnected the alarm did not go off. I realize it is hard to have more than 1 mechanic working on a motor but simply would like to know if there is anything we could be overlooking before pulling the powerhead as that increases the odds ,(.as well as the expense).of possibly scrapping the engine Thank You for your time.

 

[rodbolt]

Re: 2nd opinion on yam 115 overheat

before I pulled the power head I would find out which bank was setting the alarm.
then I would pull the covers and cylinder heads and look fo scale build up.
the switch closes and allows a current flow from the keyswitch through the alarm through the switch to ground.

 

[mthomas]

Re: 2nd opinion on yam 115 overheat

thanks i will try that.