Overheating at High RPM

[mohawktoad]

Hi Guys, I have a 1997 Yamaha 115 Saltwater Series Oil Injected 2-Stroke.
The motor will run great all day long under 2600rpm, but once I try to run it at a normal speed higher than 2600 it's not long (about 2 minutes) that the tempature alarm goes off & I have to shut it down to cool. The water pump has been changed a few times & it still has the same problem. It's possible that they may have not have changed the plate that comes in the kit. Besides that, I don't know. Maybe the thermostats, but I'm just guessing now.

 

[hurricane34]

Re: Overheating at High RPM

well ok

 

[Yamajoe]

Re: Overheating at High RPM

remove the thermostat and test before you check the water pumps; when you have the stats removed flush with water.

 

[Yamajoe]

Re: Overheating at High RPM

also check your pressure control valve

 

[mohawktoad]

Re: Overheating at High RPM

I did pick up a set of Thermostats just in case so I will try that first. I didn't think of the Pressure Control Valve. Thanks...

 

[zzzzz]

Re: Overheating at High RPM

if the 'stats don't do it you may have to pull the cylinder heads,split off the water jacket covers and clean the cooling passages...you can pull up parts diagrams at yamaha-motor.com

 

[scottfromoz]

Re: Overheating at High RPM

see my thread below...I had to do the poppet valve and that increased the rpm overheating to 5500rpm...I then took of the head covers (not the heads themselves) and cleaned out the water galleries - several small holes junged up with crap...back out on the water with nice clean galleries and new gaskets and 5500rpm for 10 mins and no overheat...nice

Cheers and good luck...let me know if you want to know anything else..I used a nylon brush bit on a drill to give it a good clean.

Cheer

PS. 93 115 2 stroke yammy here

 

[zzzzz]

Re: Overheating at High RPM

Scott- if you found the water jacket passages clogged to some degree then why would you not think the same of the passages in the head and the block itself ?

 

[scottfromoz]

Re: Overheating at High RPM

Here is a pic of the most affected side - after cleaning. The 2 holes in the very centre between the 2 cylinder heads that look like bolt holes are water holes...the one on the right was the most blocked - basically wholly blocked.

I had been told that it was the tightness of the galleries in this area and in the cover plates themselves that is usually the problem and not the rest of the motor - to do with the tight design of the V4.

The proof seems to be in the pudding because it no longer overheats even at 5500rpm flat knaker for some distance...

One day if she even heats up again (ie sooner than later say in a year or 2) then I would remove the heads and exhaust manifold and have a Captain Cook and a clean out...in the meantime dont touch if it aint broke.

Cheers