CaribouHills
Recruit
- Joined
- Jun 2, 2004
- Messages
- 5
I have an over heating problem on a Yamaha 70hp, 2 stroke, but only at idle speed, in gear. The motor is a 03 model (70TLRB) and has approximately 700 hours on it. This motor is ran in fresh water only. Let me give you a little history here if I may. I have been working with two Yamaha service mechanics and one of them has been consulting with Yamaha regarding this over heating problem, but unfortunately the problem still exists. Things that I have tried thus far: drilled by-pass hole in the thermostat, which didn't work, then replaced thermostat. Rebuilt water pumps numerous times, including pump housing with Yamaha parts. Removed the gasket below the pump housing, which helped but did not cure the problem. Stopped using silicone on the pump housing bolts and cleaned all bolt holes. Installed new pump housing bolts, just in case the old ones had stretched. Used compressed air to blow out the cooling system. Increased oil injection pump. I realize that I could change prop size and possibly cure the problem, but that is an option I would rather not take if possible, due to the usage of this motor. I am currently using a 13 5/8 x 13 prop, which drops the rpms by 150 when in gear at idle speed. On the 04 model 70s, Yamaha changed the size of the pump impeller and pump housing, which makes me wonder if there was an over heating problem on all earlier model 70s. Is it possible to cause over heating by increasing the oil injection ratio due to having more btu's in oil? Could a non-Yamaha injection oil possibly cause over heating?
<br /><br />First suggestion.: