How hot should risers, manifolds and Y pipe get?

[JohnB.]

I'm posting about a AQ225E in a 86' trophy (yes, the one that overheated).
After receiving parts and replacing the exhaust rubber and outdrive water connecter that broke, along with checking the impeller...actually, I reversed the direction of the water pump impeller since I had just installed it before the last feasco. In addition, I changed the plugs since I pulled the old ones looking for water. Anyway, I forced water through the system to insure the pump had some by clamping a hose to the water pump intake hose as before and ran the motor. Then I hooked the water up through the ears and ran it that way....this is the root this question:

When the motor first starts running with water through the ears I can see a good flow through the side flappers of the out drive. After a couple of minutes this flow seems to deminish to an intermittent spray. Then after a few more minutes it seems to pick up again and look more like steam then water spray then come and go between steamy water flow and spray. In the mean time the risers manifolds and Y pipe seem to be getting fairly hot....not so that I can't hold my hand on there for a few seconds but hotter then I can remember. However, I don't have a good point of reference here because I don't remember spending a lot of time with my hand on the risers before and may be mistaken as to how hot they got before. The temp gauge rose up to around 175 and seemed to hover but when it looked like it wanted to creep higher I shut it down.
So how hot should the manifolds, risers, exhaust rubber and Y pipe be getting? Should the tattle tail water flow be intermittent and have some steam involved? Could this be a thermostat failure? I was also wondering if the thermostat opening and closing would reflect in intermittent water through the tattletails? Any info would be most appreciated.

 

[HT32BSX115]

Re: How hot should risers, manifolds and Y pipe get?

Howdy,

It sounds like you may have some blockage in the raw water cooling circuit......like water pump remnants from a previous pump failure?

175* (if that is accurate) is a little high (if this is happening only on an adapter and hose it might be ok)

If it's getting that hot in the water at low RPM it might be a little high. (you should verify your gage before you get too worried about it)

It's unlikely a thermostat would cause the manifolds and risers to get hot since it only regulates cooling water thru the block, not the manifolds/risers.

Did you verify good water flow from the raw water pump by disconnecting it at the T-stat and briefly running the engine?

 

[captmello]

Re: How hot should risers, manifolds and Y pipe get?

That motor should have a 160 deg. thermo. Can you verify that it does? If not, I'd change it. Your gage could be wrong, changing the thermo could verify that.

Sorry to say, I think you should change out the impeller again. With the issue you had with the fitting on the outdrive, you would have been starving the impeller of water, and it may have overheated as well.

The water flow from my boat is very much like yours running on muffs. The manifolds seem to vary in temp, but I can always put my hand on them for a couple seconds. We either have the same problem or they are okay. I'm hoping for okay.

Some guys use an IR temp gun to check temps at various points on the motor. Got one of those?

 

[JohnB.]

Re: How hot should risers, manifolds and Y pipe get?

No, I don't have a temp gun but after reading in hear how handy they are I think I'm in the market. Any advice on a good place to get one?
So If I have a 160 degree thermo that allows the core temp to regulate at around that temp....does that also mean I should see 160 degrees at the manifolds, risers and Y pipe? What reading should concern me on the temp gun?
I'm curious...when you run your system on muffs, do you also block that pee hole at the bottom of the lower unit that points straight down (with the lower unit lowered)? Sometimes it seems to make a difference how much water is picked up. Also, about the impeller...I was wondering what I should be looking for in the way of damage. I checked this one for brittleness by bending the lobes but it seemed plenty plyable and had only the slightest buffing from rubbing across the constrictor in the pump....but I flipped it anyway. Do you think there would be some molecular damage that would make it prone to failure?
I take it that when you say the water flow is simular with your system that you also see intermittent flow, sometimes strong and sometimes weak with marginal steam present (or hot water on a cold day appearance)?
I truly appreciate you responding...thanks!

 

[Howard Sterndrive]

Re: How hot should risers, manifolds and Y pipe get?

not so that I can't hold my hand on there for a few seconds .

If you can hang onto something and even apply a bit of pressure without it scalding your hand, it's below 140F.

If it's painful to keep your fingers resting against it, you are over 165F.

If you spit on it and it fries, that's over 212F

If the paint is turning brown, that's over 290F

I have an IR gun somewhere, but I rarely need it

 

[bruceb58]

Re: How hot should risers, manifolds and Y pipe get?

I'm curious...when you run your system on muffs, do you also block that pee hole at the bottom of the lower unit that points straight down (with the lower unit lowered)?

yes...you are supposed to block that off.

 

[JohnB.]

Re: How hot should risers, manifolds and Y pipe get?

Well, to put this thread to bed......it's ending on a positive note.
Turns out all that overheating and intermittent water flow (this part I don't understand) was the thermostat. I did all the checks to eliminate any blockage....back flow under pressure through the lower unit to check for leaks and blockage, running with the thermo hose off to check pump impeller, checking all the hoses to the thermo block for chunks, the only thing I could find wrong was a crudded up thermo that probably should have been changed a decade ago. I don't know if the outdrive hose connecter failure cascaded into the thermo failure due to the overheat or if the thermo failure was the actual cause of the overheat and the hose connecter crumbling was coincidental....but what the hay.....I just ended up replacing stuff that probably needed it anyway (I'll keep telling myself that).
Anyway....replaced the thermo and got steady water flow out the back and the gauge bounces between 140 and 160....I think I can live (and boat) with that!!!