Update! Alarm what's next ! Tests today

[Steveditt]

1998 saltwater S175 HP TXRW today with Thermal Temperature gun in hand expecting to find one bank of cylinders clogged causing the overheat alarm ,I’m somewhat convinced that’s not the case . As previously noted new thermostats and water pump were installed spring 2017 boat was used during May and beginning of June when the alarm sounded . Today
Ran the engine at the dock at idle 40 minutes as I keep checking temps 135 -140 the lower cylinders were cooler than the top near the thermostat but remaining 135 -140 increased in neutral to 2500 RPMS 15 minutes keep checking engine temps remained the same on both sides 135 -145 now lowered back to idle keep checking after a few minutes both sides started increasing 140 -150 -160 -170 -180 alarm -190 same on both sides turned off . Let it cool down 25 minutes started reading 125 within minutes increased right back to 190 shut down .
After cooling connected the flush line to a hose but didn’t turn in on now with the engine in the water started the engine and again temps quickly raising I then turned on the hose while the engine was running the temps cooled from 180 to 150 .
So could it be a bad pressure relief valve Poppet ? Arriving today the valve was open or closed confused about the valve but the engine should have overheated well before a hour of running but once that value open or closes it constantly would overheat and quickly just like the day on the water last week ,we traveled 1 ½ miles in a no wake zone no alarm , after a few minutes on plane alarm then letting it cool 20-30 minutes once started at slow speed within minutes back to the alarm and Boat U/S tow.
I ordered Rydlyme Saturday if I had to bring it home as I expected I would , I have a new poppet valve which of course I never installed I turned the nuts so that’s good start I’m over an hour away from the boat but soon I’ll change the valve . What do you guys think ?

[FabricGATOR]

The flush tube connection, when disconnected from the garden hose and stowed (screwed) onto the engine is simply plugged. The male fitting on the cowling goes no where, it is simply a cap off of the cooling water from the water pump.

The pop off valve is a pressure regulating valve that wastes off any excess cooling water that the lower unit water pump produces. Think of it like a spring loaded ball pushed against the end of a garden hose... when the hose (cooling water) pressure exceeds the springs ability to hold it back, the excess water escapes past it. The parts consist of a spring, a housing, a rubber seat, and the plunger that acts like the ball in my explanation. When I serviced mine, I found I also needed to replace the housing and hose because it expanded/deteriorated from corrosion and the swelling deformed my hose. The hose routes the wasted cooling water out of the engine cowling into the (I believe the two square) exhaust ports on the upper casing.

Atop both cylinder banks is a bolt with a washer seal. That is where a cooling water temperature sensor could be installed to transmit that information to a gauge at the helm. It could also be a cooling water pressure gauge. So if you were to temporarily connect a pressure gauge at that port, it would give you an indication of the poppet valve and water pump efficiency, although I do not know what that data range should be.

You did get results from adding additional cooling water to the water jacket. That is what you did when you turned on the hose and saw the water temperature go down. So, what does that mean... I would suspect that maybe your waterpump is not fully supporting the cooling required, OR maybe the poppet valve is letting some of that water escape, OR possibly your hose water is really cold from a deep well and cools better than Tampa bay water... How much hose did you apply? Full on pressure? I wonder if it exceeded that capacity of the poppet valve to drain off waste water pressure and pushed more water through than designed.

The folks at Ridlyme claim that you can't go wrong using their product. If you ask around, google, or contact them, I think there is literature about using it on outboards. I also believe that Yamaha coats the water passages with Epoxy, so as long as that coating is in tact I believe that would even stop harsh acid at that epoxy barrier.

Did you do this afore mentioned test with the thermostats installed?

[FabricGATOR]

http://www.rydlymemarine.com/assets/...structions.pdf

[TownsendsFJR1300]

http://www.rydlymemarine.com/assets/...structions.pdf

Question, (just looked at the above instructions).

Is there any reason why you simply could not use the Powerhead FLUSH attachment (don't go thru the muffs).

Remove the thermostat, use a catch pan, and a re-circulation pump.

Pump from the catch pan back to the flush port?

What would be the downside (short of it being WAY EASIER) AND YOUR PUMPING direct to the powerhead
(which is where the salt builds up)?

[Steveditt]

Overheat

Full power from the hose , Water pump was a complete kit which went easy and I've used over 60 gallons since installed without a problem until this . Seems strange that the engine ran at idle for 45 minutes today without a problem low temps using the thermal gun ,increased to 2500 still low temps reduced back to idle and I don't remember how long after but both sides of the engine increased to 190 ,cooled down to 125 restarted within minutes right back to 190 . WP I would think would be constant . I have a poppet which of course had planned on installing and never did so this could be the first time its been changed .Thanks again for your insight ! Hopefully tomorrow I'll change the valve and see what happens .

[fairdeal]

Question, (just looked at the above instructions).

Is there any reason why you simply could not use the Powerhead FLUSH attachment (don't go thru the muffs).

Remove the thermostat, use a catch pan, and a re-circulation pump.

Pump from the catch pan back to the flush port?

What would be the downside (short of it being WAY EASIER) AND YOUR PUMPING direct to the powerhead
(which is where the salt builds up)?

the only difference I can imagine, is you might get better "coverage" their way-

since the liquid would be "rising up from below" -
which has to fill all spaces -

as opposed to possibly "trickling down from above" via the flush connector

If I were doing it - I wouldn't mess with muffs -

I would drop the LU

and connect my temporary pump discharge to the water tube.

[pstephens46]

As Oldmako might say, this is way too pedantic. I feel like whatever is used that is strong enough to remove the deposits may very well harm the aluminum engine and seals. I would be prepared to possibly break a few bolts but would disassemble and scrape the crap out. If you don't get most out with chemical bath, you may we'll be doing this again soon. Barnacles like other barnacles....

Devils advocate....

[Jason2tpa]

I don't think the result of introducing an increased amount of water flow to the cooling system, that is a higher flow rate than the water pump is capable of achieving on its own, can be considered a valid diagnostic finding. Simply because the increased flow rate the cylinders are receiving could remedy the issue that's causing the high temp alarm, essentially masking the problem.

I'm not implying all causes of the high temp alarm would benefit from a higher flow rate. For example, a corrosive blockage in the cooling system causing the overheating might be so far along with corrosion that no additional amount of flow would provide remedy. But catching a cooling system problem in its infancy, whether corrosive blockage or a water jacket leak, could very well become masked by applying an increased water flow rate to the engine. At which point, you'd then overlook the aforementioned problems because the added flow rate solved the symptoms. But as soon as you remove the added flow rate, thereby allowing the water pump to sustain full cooling responsibilities, I recon the high temp alarm would return.

Since you already have a spare poppet valve it's no harm to replace the old ones and see if this is the fix. However, having a model/year engine very similar to yours I think the primary cooling issue stems from corrosive blockage.

6 months ago I replaced the head gaskets on my engine, but not because they were worn or leaking. They were definitely old, even a bit crusty. But I wanted to head off a potential future problem from occurring by pulling the heads, assess the corrosion, and replace the gaskets. Before pulling the heads I never got a high temp alarm. Be that as it may, there was definitely a lot of corrosion built up in the system. I was lucky that I addressed it before it became an issue.

[Jason2tpa]

I don't think the result of introducing an increased amount of water flow to the cooling system, that is a higher flow rate than the water pump is capable of achieving on its own, can be considered a valid diagnostic finding. Simply because the increased flow rate the cylinders are receiving could remedy the issue that's causing the high temp alarm, essentially masking the problem.

I'm not implying all causes of the high temp alarm would benefit from a higher flow rate. For example, a corrosive blockage in the cooling system causing the overheating might be so far along with corrosion that no additional amount of flow would provide remedy. But catching a cooling system problem in its infancy, whether corrosive blockage or a water jacket leak, could very well become masked by applying an increased water flow rate to the engine. At which point, you'd then overlook the aforementioned problems because the added flow rate solved the symptoms. But as soon as you remove the added flow rate, thereby allowing the water pump to sustain full cooling responsibilities, I recon the high temp alarm would return.

Since you already have a spare poppet valve it's no harm to replace the old ones and see if this is the fix. However, having a model/year engine very similar to yours I think the primary cooling issue stems from corrosive blockage.

6 months ago I replaced the head gaskets on my engine, but not because they were worn or leaking. They were definitely old, even a bit crusty. But I wanted to head off a potential future problem from occurring by pulling the heads, assess the corrosion, and replace the gaskets. Before pulling the heads I never got a high temp alarm. Be that as it may, there was definitely a lot of corrosion built up in the system. I was lucky that I addressed it before it became an issue.

[99yam40]

I am thinking the PRV sticks some time.
dumping too much water and then it overheats

[FabricGATOR]

Steve, if / when you go after the poppet valve, make sure you have part's 22, 23, 24 or at least #23 the grommet and #24 the gasket. I suspect that you'll likely find the valve itself #21 is a hard piece of plastic that really doesn't deteriorate.

1998 S175TXRW Yamaha Outboard CYLINDER CRANKCASE 2 Diagram and Parts

And like 99Yam suspects, inspect / evaluate the #25 cover to ensure that the valve is not hanging open because that is all corroded up. I had to replace mine as it had expanded from the corrosion and also deformed my hose #28 had to be replaced too.

Not sure if I asked, but when all the dust settles and you have it fixed, please return back and let us know what your conclusion was as to the repair.

[FabricGATOR]

As Oldmako might say, this is way too pedantic. I feel like whatever is used that is strong enough to remove the deposits may very well harm the aluminum engine and seals. I would be prepared to possibly break a few bolts but would disassemble and scrape the crap out. If you don't get most out with chemical bath, you may we'll be doing this again soon. Barnacles like other barnacles....

Devils advocate....

I disagree to the extent that mechanical scraping, or "Rodding out" as was the terminology of inboard exhaust risers and manifolds.. all that scraping is going to mar the epoxy coating that Yamaha installed to stop salt water corrosion from reaching the aluminum.
The Rydlyme or even the citric acid treatment that Mercedes directs to be performed on aluminum radiators is not going to harm the engine or epoxy coating like a coal miner with a pick ax and chisel will.

Rydlyme describes the action to be like dissolving of a cough drop or hard candy in your mouth.

I was skeptical, I still am. I just bought a few pounds of Citric acid from amazon even though I still have three gallons of fresh Rydlyme left over from my 5 gallon carboy container.

Barnacles like barnacles, I agree with that in that half measures with give varied results. I also have concerns that have been addressed about not getting fluid flow in nook's, cranny's, and areas of low flow.

I did let it circulate for an hour or so and then shut it down and look in through the thermo hole for results. It was slow going. After several hours it cleaned up pretty good although there was still a little calcium deposit and I was to tired to mix another batch to continue. and too impatient.

I am wondering about my internal engine anodes.

[TownsendsFJR1300]

^^^, I would think the internal anodes should be similar to the one's accessible form the outside(if we're on the same page). Inspecting those before(too late now) and after should tell the tale.

From previous posts nere, the citric acid seemed to do an excellent job


Fabrigator, did you drop the LU, use the flushing device only, or?

[pstephens46]

I seem to remember someone posted about BAKING (maybe braising is the word) his heads in an oven with citric acid....Sure the wife was thrilled. Seemed to work from what I remember about the pics.

[TownsendsFJR1300]

I seem to remember someone posted about BAKING (maybe braising is the word) his heads in an oven with citric acid....Sure the wife was thrilled. Seemed to work from what I remember about the pics.

Yep, post #21:

http://www.yamahaoutboardparts.com/f...h27868-p2.html