1999 Yamaha 200 OX66 --- Overheat Alarm above 4000 RPM

[Getn Busy Livn]

I recently purchased a set of 1999 Yamaha 200 HP OX66 motors for my center console and this weekend I had the overheat alarm go off twice after extended running (15 minutes continous) at rpms above 4200. I removed the cowling and the head seemed pretty warm but the tell tale pee-stream seemed fine. The oil levels in both resevoirs was perfect so I'm pretty sure it was an overheating alarm/issue.<br /><br />The strange thing is if I kept the rpms under 4000 I could run without the alarm sounding the entire trip. Plus I never received another alarm even after idilling for 6 hours straight. <br /><br />The previous owner seemed to have taken excellent care of the engines (he gave me all the service records) so it appears that the impellers were changed during the last annual (roughly 25 hours ago).<br /><br />Is this an impeller issue or am I dealing with something more serious? I was planning on doing the impellers within the next couple weeks anyway but I'm hoping you guys can help me troubleshoot this issue. <br /><br />Thanks in advance!

 

[rodbolt]

Re: 1999 Yamaha 200 OX66 --- Overheat Alarm above 4000 RPM

hello<br /> the 2 normal causes of overheat above 4000 are bad pumps or clogged cyl and cyl head cover passages. first insure the pumps are done with OEM kits and the housings are not melted then insure the temp switches are working properly with hot water and a candy thermometer and after that its about time to pull a head. a clogged filter in the remote oil tank will give a similar alarm scene. what did the visual indicator on the tach tell you?

 

[Getn Busy Livn]

Re: 1999 Yamaha 200 OX66 --- Overheat Alarm above 4000 RPM

I will definitely replace the Impeller Kit and check for any melting within the assembly. Where would melting usually occur? --- the Water Pump Housing? or within the O-Rings?<br /><br />When you mention Temp Switches do you mean the Thermostats? If not ---- what and where are the temp switches located?<br /><br />I didn't even think to look at the Tach when the alarm was sounding because I didn't know the Tach would indicate an Overheat Alarm. Is there a symbol that appears on the Tach when the alarm occurs?<br /><br />Thanks for all your help. I'm hoping to all of the maintenance on these motors because finding a good, trustworthy mechanic has been challenging in this area.

 

[rodbolt]

Re: 1999 Yamaha 200 OX66 --- Overheat Alarm above 4000 RPM

depends on which tachs you have. on the older tachs only the oil alarms visual indicate is present, the temp visual is in the speedo. the melt will be in the pump housings if present. the temp switches are in the cyl heads with pink and black wires.

 

[Getn Busy Livn]

Re: 1999 Yamaha 200 OX66 --- Overheat Alarm above 4000 RPM

Rodbolt .... Installed a new Water Pump Housing and Impellar Kit. The housing did show some small signs of damage and the Impellar definitely needed replacement. <br /><br />Thinking I had the cause of the alarm licked ... I put the boat in the water and fired her up. The water flow from the tell tale still looked a little weaker than my port motor but when I increased the rpm a little it looked very strong. <br /><br />I let the motor idle for about another 5 minutes while I cleaned up the boat some and then I got the overheat alarm again! This time I confirmed that my temp gauge showed the elevated temp. I immediately shut the motor down so as not to hurt anything.<br /><br />You mentioned that the thermostat and/or temp switch could be bad also. I bought new thermostats and gaskets when I bought the Impellar Kit because I was planning on changing them anyway. I didn't look at the Thermoswitch yet ... but it seems I'll have to know to continue the process of elimination.<br /><br />I saw in another post where you suggested the problem could be with the Poppet Valve (?sp) ... could this be my issue as well? <br /><br />I feel like I'm quickly getting over my head in trying to diagnose this issue .... your advice is greatly appreciated!!!!

 

[fisherman11648]

Re: 1999 Yamaha 200 OX66 --- Overheat Alarm above 4000 RPM

Mark, I had the same problem on my Yami. So took heads off and cleaned the water passages.. Took off the water jacket covers and cleaned them real good. put it all back together.Changed the popit valve. Now it runs like a top again..This is not a hard job to do. Good luck

 

[Getn Busy Livn]

Re: 1999 Yamaha 200 OX66 --- Overheat Alarm above 4000 RPM

--------- U P D A T E -------------<br /><br />Well after getting the overheat alarm at the dock at a fast idle I decided to remove and replace both Thermistats which appeared to be in pretty rough shape (scale buildup).<br /><br />I also pulled the Thermoswitches from the block and I just finished the Continuity test oulined by the Service Manual and Clymers. Per the spec, each sensor gives continuity at a temperature around 180 degrees F.<br /><br />I didn't have a chance to water test it with the new Thermistats in place .... I'm hoping that corrects the issue!<br /><br />If it doesn't what are my other options .... the poppet valve? then cleaning the water jackets?<br /><br />Look forward to hearing your sugestions.

 

[kavika]

Re: 1999 Yamaha 200 OX66 --- Overheat Alarm above 4000 RPM

I had similar with 1997 200 SW II. After checking everything, ended up pulling head cleaning blocked passage under sensor.<br /><br />Mechanic said since blockage was under sensor and engine depowered before any real overheating took place...everything should be OK. <br /><br />I hope!

 

[Getn Busy Livn]

Re: 1999 Yamaha 200 OX66 --- Overheat Alarm above 4000 RPM

Aquasport and Kavika ..... seems likely that I'm going to have to pull the heads. I was wondering how difficult this job would be?<br /><br />When you say "pulling the head" I'm assuming you mean the Water Jacket Covers. I'm using both the Clymer and Yamaha Service Manuals and the Clymer manual lists the outer most part (where the Thermostat is installed) as the Water Jacket Cover. Removing and cleaning that seems fairly straight forward but if I have to go further than that I think it's time to call a mechanic. <br /><br />Is that what you guys are talking about or did you remove everything down to the Block? <br /><br />Assuming that it's only the water jacket that needs to be removed ... how did you clean them?

 

[kavika]

Re: 1999 Yamaha 200 OX66 --- Overheat Alarm above 4000 RPM

I applied green poultice [$400] to O'Neals mechanics hand, after I checked everything else.

 

[fisherman11648]

Re: 1999 Yamaha 200 OX66 --- Overheat Alarm above 4000 RPM

Mark ,,, Take off water jackets.. I think 6 bolts per jacket. No problems.. I cleaned them by beading them,, kinda like sand blasting but not the same.Ask somebody or a machine shop. Next the head covers under the Jackets 8 bolts per head I think. When off you will be able to see the tops of pistons. My sensors just pulled out of heads. a Torque is the most important tool you'll need. Refer to manual. This is not a hard job at all.. But if your uncomfortable get a machinic and watch him for the next time. Cost should be around $300-$350.. Good luck And dont worry.. Just do it.