Reply To: 4LHA-STP engine overheating

[Bill Fuller]

Nick,
I have been running a set of these motors for almost 19 years now with 6,000+ hours. I few thoughts for you and questions.

1. The coolant you mentioned, I am not familiar with it. Is it an extended life coolant? Does it state specifically that it does not contain silicates or phosphates, this is very important. What color is it?

2.. As for the raw water pump, they are really a superior unit. No cam plate to cause problems, nice solid bronze construction, bearing and seals seem to last forever. I have yet to rebuild one. I would suggest that you purchase a set of Tonys impellers, they are far superior to the ones Yanmar sells. In fact, I would replace your current impeller and recheck your temperature before going much further. I have personally seen the Yanmar impellers stop pumping properly in a very short time. And when removed look just fine.

3. Pump removal suggestions. It sounds like you have never removed the raw water pump from the engine. A few tips. Remove he alternator or move t out of the way. Remove the bracket that holds the alternator. These are easy to do and greatly increase access to the nuts and bolts that hold the pump. There are 2 bolts and 2 studs that hold the pump. Check the wear plate below the impeller and turn it upside down. Now you have a clean surface against the impeller. Polish the inside of the cap. If the housing of the pump shows scoring or wear, polish it too, most likely not needed. But do replace the impeller and check again.

4. Still on the pump, as an example, not too long ago when I was doing my yearly maintenance, which includes an impeller change, Tony was out of impellers and I used Yanmar parts. After about 200 hours, I started to notice more than normal steam out of my port motor. The steam increased on the next trip to where I was concerned. No noticeable engine temp increase. Water flow “looked” fine. Pulled the pump, impeller looked perfect, changed it anyway problem solved! As a side note, I will never “look” at an impeller without changing it.

5. Buy impellers from Tony. I think you can order online.

I had more thoughts but now I can’t remember them. Enough for now anyway. If you have any questions I will be glad to share knowledge I have gained over the last 19 years with these motors.

Bill