Exhaust water

[BQUICK]

When should water flow out of the two exhaust ports on a 1989 200?

Thermostat open or PRV open?

Mine has water coming out of one motor at hot idle but not the other motor.

[boats.net]

It's a relief hole, if can't get through prop then will come out that hole.

[BQUICK]

Not temp based? Is the water excess water pump water or water that is bypassing tstat or PRV?
Still wondering why one would do it and not the other....

Thanks

[DMSOUTH]

The pressure relief valve is used more at high speed--the water pump will pump more water than the engine needs at high rpm, so the prv will open and dump the excess water. At idle, all the water that is being pumped is required for cooling, so the prv should be closed. I would suspect you have a valve stuck open on the engine that has water coming out the exhaust at idle.....
Since it is spring operated, there's probably some grit in the valve keeping it open at all rpm's...

[BQUICK]

Yeah, the motor that is pumping water out the exhaust is the motor that when I tried to change the PRV one of the bolts snapped right off. Doesn't leak with only one and can't drill out the broken one since the pan is in the way. I guess i'll leave things alone since I have no overheating alarm at idle or high speed.

[DMSOUTH]

You won't get an overheat alarm at high speed for a stuck open prv, but if it is in fact stuck open, the top cylinders may not get enough water to cool properly because the pump can't pump enough water-it's exiting through the prv instead of cooling. You may be alright if it's stuck open only a small amount, but personnally, I wouldn't take the chance on cooking a cylinder......

I'm having overheating issues with my '87 Yamaha 200hp. My question is where can I find a schematic of the water flow from the impeller until is exits through the exhaust? I have tried about everything I can think of so far. I took the water jacket covers and cylinder head covers off and cleaned out the salt that had accumulated over the last 20 years. The gaskets were original and the bolts looked brand new. That needed to be done. I have new thermostats and a new impeller kit installed as well. When I have the lower unit off and I spray water up the tube with a hose it comes out the telltale. I don't see it coming out of anywhere else but I hear it gurgling inside. I had done this with both thermostats out and the covers off. I had clean water pouring out of the holes where they go so I'm guessing the inlet tube is not cracked, broken or disconnected. With the lower unit on and my earmuffs hooked up at idle I was getting nothing out the tell tale before the work I did. Now I get smoke streaming out. The engine doesn't overheat as fast as it did but eventually gets up there. I shut it down long before that happens.

The only other thing I can think of is to take the exhaust plate off and see if there is a blockage in there. I'm sure those gaskets are shot and original ones too. Because the earmuffs pour out so much water I can't tell if any water is making it to the hub exhaust but I'm guessing not.

My other question is what does the water temp gauge read and where is the sensor? I have the two sensors on each cylinder head but I thought they were for the overheat alarm. I can't seem to find the sender for my water temp gauge or engine temp gauge whatever it reads.

[jb123]

I'm having overheating issues with my '87 Yamaha 200hp. My question is where can I find a schematic of the water flow from the impeller until is exits through the exhaust? I have tried about everything I can think of so far. I took the water jacket covers and cylinder head covers off and cleaned out the salt that had accumulated over the last 20 years. The gaskets were original and the bolts looked brand new. That needed to be done. I have new thermostats and a new impeller kit installed as well. When I have the lower unit off and I spray water up the tube with a hose it comes out the telltale. I don't see it coming out of anywhere else but I hear it gurgling inside. I had done this with both thermostats out and the covers off. I had clean water pouring out of the holes where they go so I'm guessing the inlet tube is not cracked, broken or disconnected. With the lower unit on and my earmuffs hooked up at idle I was getting nothing out the tell tale before the work I did. Now I get smoke streaming out. The engine doesn't overheat as fast as it did but eventually gets up there. I shut it down long before that happens.

The only other thing I can think of is to take the exhaust plate off and see if there is a blockage in there. I'm sure those gaskets are shot and original ones too. Because the earmuffs pour out so much water I can't tell if any water is making it to the hub exhaust but I'm guessing not.

My other question is what does the water temp gauge read and where is the sensor? I have the two sensors on each cylinder head but I thought they were for the overheat alarm. I can't seem to find the sender for my water temp gauge or engine temp gauge whatever it reads.

is this IN water on only on muffs when you have the issue

yammies need PLENTY of water flow to keepem cool.

did you only do the kit or the housing also ?

and how bout YOUR prv ?

is this IN water on only on muffs when you have the issue

yammies need PLENTY of water flow to keepem cool.

did you only do the kit or the housing also ?

and how bout YOUR prv ?

Last season I only had a chance to use the boat one time and it ran fine. I bought the motor used last June and spent most of the summer rebuilding the boat itself. Every time I ran it in my driveway on the single rabbit ear type (water only comes out one side) it idled fine and never overheated. The one time I ran it in the ocean it ran fine, the block temps never rose above 130º as measured with a thermal scanner.

This past June I went to get the boat ready and it overheated in my driveway, this time I am using the rabbit ears where water comes out of both muffs. Someone told me they were better to use on big block engines like mine. Another person told me that it doesn't matter which ones I use so long as the water coming out of my hose has sufficient pressure. I checked that too, I can fill a five gallon bucket in under two minutes.

So far this summer I have replaced the impeller and water pump housing, the thermostats and water jacket gaskets as well as cylinder head gaskets. I had the local marine repair shop do the impeller and water pump housing when they had to do lower unit work. My prop shaft and crankshaft seals were worn and I had water in the gear lube. I double checked their work to make sure they didn't do something silly and not put a woodruff key on before the impeller. I can't even get the new impeller off and it spins with the crankshaft so I'm guessing that is not the issue.

Today I brought my boat to them so they can look at it. The only thing besides a clog somewhere that I can't find is that perhaps I did not get the water inlet tube on the impeller housing. I don't see how that could be the issue since that tube pretty much lines up directly with the housing insert. Unless (as I type this it occurs to me) they forgot the grommet on top of the pump housing? That I did not look for but again I don't think that is the case. These guys are pretty reputable and people bring them boats to work on from pretty far off because of their reputation.