1995 yamaha 150 running hot

[nmhellraiser]

I'm lost here and looking for advice. I have twin outboards and the starboard motor is running hotter than the port motor above 3500 rpm's. Brand new water pump kit installed last weekend. New thermostats and poppet valve installed today. I do get an overheat alarm after a few minutes running above 3500 rpm's. The port motor runs about 140 degrees at all times and the starboard runs about 180 degrees above 3500 rpm's anything below 3500 is right in line with the port motor. The only real thing that I do notice is the **** stream on the starboard motor is weaker than the port motor. What am I missing here? It was doing the same thing before I replaced all these parts.

 

[99yam40]

Re: 1995 yamaha 150 running hot

how did the pump housing look?
sometimes they need to be replaced also if any sign of damage

Could be there is some type of blockage in the cooling passages
Parts of impeller or just salt/corrosion that needs to be cleaned out

 

[nmhellraiser]

Re: 1995 yamaha 150 running hot

Everything was included with the impeller. New housing, bolts, ect. Salt corrosion is my next suspect. Going to take the T-stats out and dump some salt away into the block and let it sit there for a while. My boat is in a dry slip so flushing is a little tough. The old impeller looked fine but went ahead and changed it all since I was there. Just really has me puzzled.

 

[99yam40]

Re: 1995 yamaha 150 running hot

Yamaha does not furnish the housing with their water pump kits, but do have the cup and wear plate included.
Plastic housing has to be ordered separately.

 

[nmhellraiser]

Re: 1995 yamaha 150 running hot

Yamaha does not furnish the housing with their water pump kits, but do have the cup and wear plate included.
Plastic housing has to be ordered separately.

Im sorry, it was a sierra kit. I was in it all weekend and friday i decided to cut up the old t-stats where it would be open all the time. Actually seemed to solve most of the problem. I can run for hours and the temp only seems to get around 160 now at higher rpm's and no alarm. Somewhere ive got a restriction internally. Guess i can pull the head covers and look. Otherwise, i might just leave the tstats open. Im in TX and the water doesnt get too cold here.

 

[99yam40]

Re: 1995 yamaha 150 running hot

Still need the stats to control motor temp even if it does not get cold where you are.

May have hot spots that can damage things if there is plugging in passages

 

[hall832]

Re: 1995 yamaha 150 running hot

Agree with 99yam on needing the thermostats even in warm water.
I have run into this problem several times. Locating restrictions in the block can be difficult.
As a last resort i have dropped the lower unit and pulled the thermostats, then flush muriatic acid
through the block. It has worked on older Yamaha's up to a 2-3 year old ETEC that was never flushed.
I really like salt terminator or salt away but as prevention.

I really like Yamaha and there parts. the few extra dollars spent on parts are worth it.

 

[nmhellraiser]

Re: 1995 yamaha 150 running hot

I'm not really going to be able to pull the lower unit with it in the slip but I can pull the t-stats again and dump something into the block and let it sit. I really might try to pull the head covers and sneak a peak if it looks like I wont snap any bolts off.