94 yamaha 150 over heating. ????

[bugeyestp]

overheating.. new thermostats... clean pressure valve. it will run all day at 3500 rpm .. at 4800 to 5400 it overheats in a couple min. I removed pressure valve and then thermostats and still overheats. what am I missing.. ?

 

[erniefish]

Re: 94 yamaha 150 over heating. ????

did you replace the water pump, how often used, vanes on water pump have lost memory, try it,

 

[rodbolt]

Re: 94 yamaha 150 over heating. ????

what your missing is a clue and a manual. like you were asked, when was the last water pump service? was the housing melted any at all?
put the pressure control valve and the t-stats back in before you post about low speed overheat.
if the pump is ok and the t-stats and pressure valve are ok I am going to go out on a limb and say this is a saltwater run engine. am I right?
I dont wish to be snippy but did the thought ever occur that the pressure control valve AND the thermostats were there for a reason ?
if they were not nessasary ya think they would have spent the money engineering,maching and installing it ?

 

[bugeyestp]

Re: 94 yamaha 150 over heating. ????

The water pump is new. only a couple hours on new pump. same with new thermostats.
I think the water jackets must have some gummy buildup in some key areas. Is there a flush that ill dissolve the gummy buildup?

Rodbolt... I posted that I was having high speed overheating only. In the past I had gained a lot of respect for you and the help that you provide, until your last post above!!!

thanks for any help

 

[parrfive]

Re: 94 yamaha 150 over heating. ????

Another satisfied costumer uh rodbolt. These people don?t work for you and most are not tech?s. Try being a little more understanding and a little more help. Bugeyestp your more than welcome to P.M. me and ill be glad to walk you through it and get you going. I am also a Yamaha dealer with over 25 years experience. And no rodbolt im not a master tech. Just a tech.

 

[pine island fred]

Re: 94 yamaha 150 over heating. ????

Stainless steel cup in the pump housing probable slipped when installed, restricting full outlet flow. Go back and check the pump and make sure the outlet is not partually blocked. FRED

 

[scottfromoz]

Re: 94 yamaha 150 over heating. ????

Mate - I was flushing recently - only after overheat at high rpm problems with Salt X- when I opened the water jackets (new impellor, thermostats, cleaned poppet valve) it looked like the Salt-x had broken down some of the salt deposits to a jelly like substance, but there was just too much caked on build up. Nylon brush bit for the drill and away I went. New gen' gaskets (highway robbery, but there you go) and a few hours work and I was back on the water - 5500rpm for several minutes and overheat gone on the 93 115 Yamm - salt builds up in the little holes that are only a bees **** across (a well hung bee).



Cheers