Engine Problems with a 150hp Yamaha

[countrytime]

I have a 150hp Yamaha 1985. It has analog gauges on it. I just recently changed both termostats. When i take it out and run it at full throttle after about 1-2 minutes the alarm sounds from the controls and the rpm drops. I can let it set for 10-15 minutes then crack it back up and as long as i run it about 3/4 throttle it will run ok. I have oil in both of my tanks. The lights that come in on my analog gauge are the green light and red light.
I am also having a problem when i stop for 10-15 minutes or more when i restart my engine, i have to pull the choke out and increase the idle speed and let the motor warm up a minute or two then it will stay running and run good. This sounds to me like i need to rebuild the carburetor. Any thoughts on these two items.
Thanks
Countrytime

 

[yamatech43]

Re: Engine Problems with a 150hp Yamaha

Did you have the problem before you changed the t-stats? Or just after? If you are not the accident prone type, you may have someone you trust
run the boat and you wait by the motor, run at wot and when problem is occuring, feel the heads with your hands...if you can't touch it for at least
3 or 4 seconds without having to remove your fingers from head then it is too hot. You can get these melt sticks at automotive parts places that
melt at different temps or buy a laser type temp gun to read temps....on the other part, you don't really have a choke although it seems like one, it's
a fuel enrichment solenoid....it makes the mix richer for starting....check your bulb, may be letting the fuel run back from engine into fuel tank while you sit(slowly) and then you have to 'choke' it to start....before you use the 'choke' pump bulb and try to start when bulb is hard....if it starts, get a new bulb.

 

[cwilt]

Re: Engine Problems with a 150hp Yamaha

i have a 150hp 2008 v-max and i ALWAYS use my choke to start. i have been dooing since the motor was new. it's a bear to start when i dont pull it out. as for the over heat, do you have the thermostats in backwards? are they the right temp? if ok you might have a water stoppage somewhere in the head. have you tried flushing the motor? how does the water pickup look? i get some fine hydrilla in mine sometimes . water pump good? what press at WOT. should be around 15 psi. how is the peehole. is the pressure ok. just some ideas for you....hope this helps