overheating problems !!

[Butty1093]

New here, be nice , i have a overheating problem on my v4 115hp yam?
At 3800rpm revs above the temp alarm comes on and goes limp mode?It was fine 3 months ago, but never started after 2 months and started first time but first time on the water alarm went off ?? Replaced thermostats , inspected water pump (perfect) ran salt away thru outboard for 8 flushes !!Attempted to test heat sensors couldn't get to work with hot water (anybody got a idea) ?
After reading many internet sites the next thing before heads inspection is pressure release valve right ??Where is it ? What should i look for after i get it out ? Any thoughts please

[TownsendsFJR1300]

Curious, is the engine used in salt water and if so, RELIGIOUSLY FLUSHED after each use?

How did the water passages look when the thermstates were out, much corrosion, any corrosion? After Salt Away?

Salt accumulation in the head and around the cylinder passages is NOT unusual if not flushed... The fix in that case (especially since the salt away didn't help) is yank the heads and manually scrape away the deposits.

[Butty1093]

I've always ran the motor in saltwater, but have always been meticulous on flushing after been out !! When I replaced the therms there was quite a lot of salt and corrosion and after a few flushes with salt away , checked again there where a lot cleaner !! So obviously if you do the heads you buy a head gasket kit (best place anyone) , just a bit worried on damaging the bolts thou !! Hav you heard of poppit valve ( pressure release valve) where is it ?what are the signs when I find it that is gone ? Thanks

[TownsendsFJR1300]

I don't know where the Poppit valve is on your engine, someone else will need to chime in.

Should the valve not help, prior to possibly pulling the heads, check these threads, similar procedure that you did but MUCH more involved and successful..

http://www.yamahaoutboardparts.com/f...g-th19434.html


http://www.yamahaoutboardparts.com/f...m-th23666.html


Should you need parts, up above in red is "Purchase Yamaha Parts". This forum operator and the prices are better than a dealer and a bit cheaper as well. You can click on that, pick your engine, then check the parts fisch for what you'll need and it does help with later work you may be doing....

[Sequoiha]

Pressure control valve is in the same place as a v6, lower starboard rear of block, and yes it can cause an overheat condition.

[Butty1093]

Thanks for the info, I read the links they where awesome. Looks like I'm going to try rydlyme , just curious he didn't have his motor running when pumping rydlyme thru his motor just the pump of the bilge !! Is this correct ?

[TownsendsFJR1300]

Thanks for the info, I read the links they where awesome. Looks like I'm going to try rydlyme , just curious he didn't have his motor running when pumping rydlyme thru his motor just the pump of the bilge !! Is this correct ?

Yep! I think he used an electric bilge pump...

And of re-cycling it with a container under the engine, catching and re-pumping it..

[99yam40]

from what I have read the PRV can cause over heat at low RPMs if it sticks open.
It tends to be that corrosion under the grommet squeezes the grommet causing it to grab the spring loaded valve not letting it close off as it should. it does not sound like what your problem is, but it is always good to check it for its condition. be careful you do not loose the grommet inside the motor when taking out and putting back in. many have done than.

I have dropped the lower unit on motors and removed the stats, rigged up a hose to the water pipe heading up to the power head. Turn on the water hose letting lots of water to flush up through the power head and out the stat holes and then inject compressed air into the hose right before it hits the pipe in spurts. It tends to cause lots of turbulence inside the motor helping to flush out build up laying in the bottom areas and flushing it out better than just water flow.

I did this on my brothers C60 to cure its higher RPM over heats and it work on a friends 90 Evinrued also.

Something to try before using the rydlyme.
Make sure you catch all of the cleaning solution when flushing with rydlyme as they run that for fairly long periods of time

Good luck and let us know how it works out

[rodbolt17]

at high speeds you can toss the pressure control valve in the creek, its not your issue.

typically your symptoms require removal of the cyl heads and covers and manually scraping it clean.
I am doing a pair of 89 200's now that were packed with scale/small shells and rocks.

its not uncommon with all makes.