Yet another TEMP alarm on 135 Optimax

[Billfo]

I have read alot of threads of people with temp alarms going off "constantly" and some temp alarms not going off at all.. Here is what happened to us today FIRST TIME OUT THIS SEASON...

Let motor warm for about 5 minutes. Visual Pee stream from outboard. Running about 5500 rpm for about 5 minutes when the alarm sounded & rpms dropped to around 1500... pee stream still present. Shut off motor. Restarted fine, ran on low rmps (going back to ramp) when temp alarm sounded again.. Shut off motor, restarted after a couple of minutes.. Ran about 4000 rpms back to marina ( a few minutes- STILL ran great).. decided to head back to ramp.. All was fine , then it happened again at low rpms)..

So, the alarm sounds on high rpms AND at low rpm, ONLY after running a 3-5 minutes..
History: Bought used in late fall. Only taken it out twice. NO alarm issues. Over the winter, I changed the injection oil from Quick Silver to the Optimax synthetic (per dealer recomendation).. Winter gas has stabil AND seafoam in it. (yeah, I know).. I have NOT changed the plugs.

The boat starts right up first time everytime. No smoke, sounds smooth,fairly quiet, 5500 RPM , 32 gallons of gas, full loading two people all the junk. Heavy chop water with occasional white caps. Water 50 degrees.

Any suggestions where I should start.
Replace impeller? I dont know how old this one is.
Replace plugs ? Could they be laboring to burn of the crap?

Thanks for the help,
Billfo

 

[Barnacle_Bill]

Re: Yet another TEMP alarm on 135 Optimax

Replacing the impeller and thermostats would be a good start. Especially since you don't know when they were last changed.

 

[Billfo]

Re: Yet another TEMP alarm on 135 Optimax

The thermostat for lower rpms & the impeller for higher rpms right ?
So there is a good chance that BOTH could have gone bad at the same time ?

Could a POPPET VALVE problem signal a temp alarm at both low & high rpms ?

Replacing the impeller and thermostats would be a good start. Especially since you don't know when they were last changed.

 

[IGIFF]

Re: Yet another TEMP alarm on 135 Optimax

First thing to do is run a DDT on the motor and find out what the temp sensors are saying(there is one on each head).This will tell you if there is in fact an overheat or if a sensor is out of range.If both indicate the same temp then you have an overheat situation where as if one is very high,then chances are the sensor is bad or there is a blockage to one bank.The DDT can tel you a lot of things to take the guess work out of repairs.

 

[Billfo]

Re: Yet another TEMP alarm on 135 Optimax

Ordered a water pump KIT & two thermostats from iboats.com store..

Does not sound too hard, wish I had a book or something for reference ***. I have never done this before, but since I plan on keeping this rig for a while- I may as well know how to do these "routene maint things".
Will find torque specs before I start.. I think I can get to all this NEXT week..
egads !!!!
Found a service manual for my Optimax on Ebay !!! AND found YOUTUBE videos of "replacing thermostats" and "replacing water pump kit"... The videos are for a Mercury 150, but the procedure has to be close ( dispite the guy NOT using a torque wrench)..
***

 

[tal]

Re: Yet another TEMP alarm on 135 Optimax

Hi there, did you take it in to be sure it was an overheat alarm? I have a 07 200hp opti with low hours. First time I pulled it to the coast I was getting a constant alarm getting up on plane. It would go into guardian mode and limit rpms to 2500. If I backed off the throttle the alarm would go away and let me run normal. After being given the run around from the dealer we bought it from I decided to take it to another merc certified mechanic/dealer. I ended up paying for an hour of mechanic labor for him to ride on my boat with his laptop and diagnose. I wish I had that software and hardware for my laptop, it tells a lot of information about the engine. He could tell the water pressure was low and one side of the engine was running a bit cooler than the other. I agreed to let him work on it. Turns out we had seaweed and a small stick (a little bigger than a match stick) jammed in one of the thermostats. This was holding the thermostat open and making the system throw a low water pressure alarm. Funny thing is, it never did it while the mechanic was on the boat with us so it must of passed most of the clog through. It never overheated but it sounded like the "constant" heat alarm. Mechanic found it by watching the temps through his tools underway, cleaned the stats, everything good now.

Might want to be sure you're getting an overheat alarm.

 

[Billfo]

Re: Yet another TEMP alarm on 135 Optimax

That software must be the "Mercury DDT" someone suggested.

I understand what you are saying to go straight to dianostics & I may end up there... But most of what I have read leads me to regular maint. replacement of thermostats or impeller, so I will change them both first. If THAT does not solve the problem, at least I only spent about 50 bucks..

I would hate to spend $200-$300 for a corroded thermostat or bad impeller...
Do apprechiate the suggestion & that diagnostic will be my back up plan..

I plan on doing this work next week, I will post my hopeful success !:redface:
Thanks..