93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

....or was it....Rodbolt you are clearly the Yammy man. Could it be that when they pulled the leg off that they checked the impeller position etc in the water pump and by so doing got it seated correctly (perhaps unbeknown to them) and when it went back together and worked without overheat they have assumed it was the poppet valve having been cleaned that did it...

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

As I understand things, my mechanic wasnt saying the poppet was stuck open, but rather it was full of old crap that was stopping it flowing through the poppet (and tube from what I can tell just looking at the valley cover between the banks)...

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

...and are Yammy V4s different in a material way in terms of poppet valve from bigger Mercs - my fella is a Merc dealer.

Cheers

 

[StinkyMako]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

 

[rodbolt]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

dunno
the pressure relief,poppit valve, is located on the lower stbd edge of the exhaust housing on V yamahas.
its also the point that the cooling water from the water pump enters the power head
all it does is bleed off excess water pressure at higher engine RPMs.
as long as you keep the engine above about 1800 you can toss it in the creek
as water pressure climbs it opens and dumps excess water into the exhaust tube area.
so at high speeds its really out of the loop for cooling.
at low speeds if its stuck or debris filled it can bleed off so much water that the top stbd cyl has no water and that bank wil over heat at low RPMs.
its funny how most techs dont even know why its there.

 

[hawilson2]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Don't know if you've already fixed yoour problem, but I had a similar problem a while ago. Seems the impeller spun off its axle. At low rpm's it had enough bite to grab and pump water but at high rpm's it spun free pumping very little water. Water pump replacement did the trick for me. May not be your problem but had similar symptoms. My 2 cents, anyway.

 

[StinkyMako]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

 

[rodbolt]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

if you can tell me how many bolts I will break I can give an estimate.
this is where the marine and automotive technicians get seperated.
for most freshwater motors its a 3 hour operation, for saltwater its time,materiels and technician skill.

 

[StinkyMako]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

 

[rodbolt]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

a chance yes, but its to easy to simply test them as they are simple on off switches or use a temp gun when the alarm sounds to verify an overtemp condition.
temp switch should close about 185*F
I use a candy thermometer and a pot of water to test them.

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

I have heard that Yammys have narrow waterways in the engine that with time build up salt even when flushed (but flushing must stretch the time out!). I have seen a 70s Evinrude 130 V4 with the water covers off the heads and the alleys there were very narrow and had salt build up. Even though mine is no longer getting hot at high rpms, I guess there will come a time when at least the water covers should come off and I should clean inside, and perhaps the heads at some point too?

My brother who had the rude paid $7 Aud for both gaskets for his water covers - genuine - but interestingly Yammy want $100 for both.....bit like a Honda car!

Cheers

 

[StinkyMako]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

 

[reeldutch]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

so what happens if at higher rpm the poppet valve stays closed or partialy closed?
Stuck with salt or other stuff?

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Reeldutch - what your saying is that my motor most likely has salt build up and its only keeping cool via a now working poppet valve? In other words you are suggesting that I strip at least the water covers off the heads and inspect and clean?

As for auto lowering RPMs it auto lowers immediately on my 93 model. It seems to cut 2 cylinders.

Cheers

 

[scottfromoz]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

Stinky - Yammys like plenty of choke when starting I understand...mine certainly does.

Cheers

 

[reeldutch]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

sorry ignor my post i was confused

listen to rodbolt

 

[StinkyMako]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

 

[StinkyMako]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

 

[rodbolt]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm

if somehow the poppit got stuck shut you would most likly see block water pressures in the 30-60 PSI range. possibly enough to force water past various gaskets but it will still cool.
with any audible alarm you should get RPM reduction if the engine is above 2500 RPM or so.
178* is sligtly out of range low and 202 is sligtly out of range high.
neither would I replace as bad based on your results.
is there a difference between a themosensor and a thermo switch.
yes, one is simply a switch, its open or closed.
a thermosensor is a sensor and has a varying resistance as tempreture increases or decreases usually used to give a controller(ECU on some equipment) information about operating temps or air temps.
not used at all on the yamaha V4.
you may have more than one issue going on.
its impreative to verify its actually overheating, then why.
its also possible its not overheating.

 

[StinkyMako]

Re: 93 Yamm 115 - new impeller and thermostats now hot over 4000rpm