Over heat alarm yamaha 90 higher RPM?

[HIFLUTIN]

Starting to get my Yammy 90 on my 170 dialed in
Getting a overheat alarm when running at a higher rpm.
Seems like the prostrate is good-(its Pissin good)
Not happened at idle
Do not have a water pressure gauge
Any obvious things could be?
tHANKS

[Blue Agave]

How old is the impellor?

[fitz73222]

Poppet valve or thermostat. Change them. If you don't know when she had an impeller last, change that too. Then you have a baseline for the cooling system. Watch the thermostat cover bolts; they're wimpy on Yammie 3 cylinder engines, so a little mapp gas torch will convince them you mean business.

[Capt Matt]

The water ports inside the motor could be crusted with salt, very common on a yamaha 90, check everything else easy first
Capt Matt

[Aswaff400]

The water ports inside the motor could be crusted with salt, very common on a yamaha 90, check everything else easy first
Capt Matt

im with matt, ive seen many get clogged up from salt/corrosion/sand. most at my work have had the head pulled and water jackets cleaned.

[HIFLUTIN]

Thanks for the responds.
Ran for a few hours Sunday morn no alarm but didn't open it up
Ive had the foot off & the Inpellor looked ok.
Goona take the cover off where the thermostate is at & check that next-
But would it effect that on a higher rpm?
The motor is a early 90s so the blockage is my next.
Hate to take the head off.
Have heard/read about some type of acid wash/flush for cleaning any idea's
Thanks

[Group W Bench]

Try several doses of Salt Away before pulling the head. Run through 3 cycles of Salt Away but mix like 20 oz per gallon instead of 2-3 oz per gallon. It's worth a shot before pulling heads. If you want to save some money and accomplish basically the same thing, just use undiluted white vinegar. Salt Away is diluted sulfamic acid, but it is pretty difficult to find. Acetic acid (vinegar) works just about as well.

[Capt. Bob]

Since you're looking at (don't look, replace) the T-stat, also don't look at part #41, as per Fitz.
http://www.boats.net/parts/search/Yamah ... parts.html

Then flush with a good dose of "salts", just like a widow woman.

You got plenty of time to twist off head bolts.

He's not the MM because he's good lookin', but for what he's tellin' ya.


I'm just sayin.

[gran398]

For the record, my wife mentioned he's good lookin'.

Back to T stats and buzzers.

[HIFLUTIN]

Thanks for the replys
You guys were right them are some "whimpy" bolts on the tsate
Had 1 snap off- Gunked with blaster-They are long & its movin
let it sit a day -hope it will come out with the adjustable metric(Visegrips)
Got link to a "Vinger" Flush on the THT-
Looks like worth a try

[fitz73222]

Some people thought the Edsel was a good looking car too, so I promise to keep my head out of the clouds! Get that damn Yammie fixed and lets see what happens... Thermostat, poppet valve and spring (#41) and impeller.

Fitz

[fitz73222]

I want to clarify something.

You have to heat those bolts up to get them out. In other words, use a propane torch and heat the area along where the shoulder of the bolt passes through the thermostat housing. Massage the torch back and forth along the entire length and focus on the shoulder area but keep the torch moving. Use a box wrench and tighten then loosen the bolt until you see the salt start to walk out of the bolt hole in the thermostat housing. Back and forth and back and forth and you will start to gain on bringing the bolt out. Heat for several minutes, shut off the torch and walk that bolt out. When it starts to get tight while backing it out, slightly tighten, heat and try again. This process is about finesse not brute strength. Use one hand only on the wrench, it will get hot; with the back and forth motion until she FREELY starts to unscrew. PB blaster has no way of getting to the root cause of the stuck bolt, which is salt that has migrated into the threads and shoulder of the bolt.  What you are doing in this process is heating the aluminum which has a faster expansion rate than the steel bolt and creates additional clearance to back out the salt impregnated threads and bolt shoulder. The screw will come out but it may take 15 minutes of manipulation to finally acquiesce to your intent. BE PATIENT. We will walk through the assembly details once you get it apart.

[gran398]

Great post Farl.

HIGHFLUTIN, if you would post the vinegar bath link, may to give it a shot on my old Johnson 25. Thanks

[slvrlng]

Here ya go Scott. Seems to work!

http://www.thehulltruth.com/boating-for ... negar.html

[gran398]

Thanks Lew!

Wonder what type of vinegar? Distilled white?

(The post didn't say)