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Very hot risers

damroc

damroc

Member
Getting really sick of boats, my 99 searay 215 5.0 thunderbolt appears to be running very hot despite changing the impeller, the thermostat (160 deg), the temp sender, manifolds, and risers. I getting plenty of water coming out both ports at the rear of the boat and removed the flow pipe at the thermostat housing and am getting a good flow of water. After removing both pipes going to the bottom of each manifold i found i could blow on the pipe and had no restictions on either riser, i can blow back through the main water feed to the stat housing with no restiction there. The engine runs smooth as silk and the oil pressure is excellent, theirs no sign of water in the oil, no signs of lumpiness you would expect with say a blown head gasket but i do seem to be gitting quite alot of steam like white smoke when i run the engine on the mufflers in my drive way. Am i write in thinking that if i had a problem with the flaps in the exhausts i wouldn't be able to blow through the riser feed pipes or aleast experience so kind of obstruction. Im completely baffled, when i changed the impeller i cleaned up the housing, removed some old coral down were the water is drawn in through the little holes on the leg and put everything back together no problem. While running the boat for say 5 minutes the temp gauge is telling me im at 170 and both pipes going to the manifolds are warmish to the touch but do not feel excessively hard or under pressure in any way, but the risers are extremely hot, and would most certinly give you a good burn if you left your hands there for a minute or two. The other thing i noticed was on either side of the lower gear casing their is small holes that water comes out of when i run the engine and cant recall weather water came out of them before i replaced the impeller. Sorry for such a long post but but as i said earlier i am utterly baffled as to why my risers are getting so hot.
Many thanks in advance and look forward to any advise possible
 
...very hot despite changing the impeller, the thermostat (160 deg), the temp sender, manifolds, and risers....
Click to expand...

The wrong riser/elbow gasket installed will impede water flow. A fresh water cooled exhaust should have two sides of the gasket open and two sides closed.

...alot of steam like white smoke when i run the engine on the mufflers...
Click to expand...

Not a problem if the air is cool. It's just water vapor forming from the mixing of hot water and cool air.

...i cleaned up the housing, removed some old coral down were the water is drawn in...
Click to expand...

Did you get all of the coral out? Pull off the water inlet hose from the inside of the transom and check the connector for blockage.
 
confused about whether this symptom is on the trailer, or running down the lake..

poor muffs, poor garden hose flow etc can make hot risers on the muffs

if running down the lake, there's a whole other set of issues with gen2 impellers at higher rpm that can be explored.
 
Thanks for all the helpful advice so far, yes Hystat i am only running in the garden on a garden hose with the mufflers so that may very well be an issue, as you know its very hard to try and explain symptoms in words so i took some video footage on my phone and uploaded it onto youtube. The first link shows the kind of pressure i have at the thermostat housing and the second one shows the boat running for a while and the white steam/smoke i was trying to discribe, any how i will try and go boating tomorrow and update you all soon. If you get a chance to have alook at the links your advanced comments would be most greatful.

http://www.youtube.com/watch?v=VQXneX8S3u4
http://www.youtube.com/watch?v=RUZ4EOE7V4s
 
Steam from not enough water ,might want to try removing the drive and putting a hose right in the inlet and retest the flow
 
hystat, the water is sourced from mains supply but strange as it may seem, the water pipie going from the lower unit to the engine is only 3/4 to inch in diameter however the feed going up to the thermostat is almost 2" in diameter. i have no alarms going off and plenty of water exiting the boat, the temp stays around 170 but the risers seem to get hot enough, am i just being over cautious ???
 
just how hot are they ?

I have been following this thread. I don't want to be accused of replying to every thread.

Beg, borrow, or steal a laser gun. Shoot the t-stat housing whats the temp there.Shoot the risers whats the temp there?
 
I watched your video's,

you have the cooling system where only cold water flows thru the exhaust from the bottom of the exhaust manifolds only and not thru the elbows directly (and thru the manifolds).

Here are my thoughts,

1. when running on a hose turn the water volume down to about 25 % of full pressure, water will squirt out of the muffs then fire engine off, confirm that the impeller sucks all the water from the water hose/muffs. You may need to rev it up to ~ 2000 rpms. If it does than the impeller is functioning properly.
If you have a soft garden hose it may collapse it. If it does not than you have a impeller issue

2. remove the incomming water hose from the thermostat housing and confirm good water flow. You may need to direct it out of the boat, (do this when cold so no overheating of engine).
The proper test is to install a clear hose in place of the rubber one and watch for bubbles in the water flow comming to the thermostat hosuing. If bubbles are present the you have exhaust gases entering water supply and this is causing the steam. If no bubbles than it may be a issue with the thermostat housing not allowing the water flow needed for proper cooling of the exhasu manifolds. Or a manifold/elbow/riser blockage.

When the impeller was replaced did you have any issues reinstalling the lower unit to the upper unit? Yo may need to drop the lower and look up at the upper and look for a collapsed rubber piece that the copper tube fits in. if that was pinched or collapsed it will restrict water flow to enigine.

Also if the water pump housing gaskets get torn this will allow exhaust gas to enter water flow.
Also did you install the small rubber "hood" on top of the water pump housing? If that is missing exhaust gasses will enter the water flow.

let us know what you find/have for answers...........
 
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Wow what knowledge we have here and how greatful am i to everyone who is trying their very best to help me, firstly i intend to borrow a heat gun tomorrow, bring the boat out to the marina and give it a run on the slip. next i checked the pipe and the sleeve going on to the top unit of the leg just incase i had some coral issues, the flow to the thermoastat would appear some what sparce but again in baseing all these faults on a boat in a garden working of a garden hose ! i can see the water feed intake pipe that runs along the top of the engine to the water the thermostat but in goes under the block at the back and cant reach the connection so should i cut the pipe to install the clear piece maybe de sure the gaskets were the right way up, the plate went on perfect and the little black seal slid down the shaft with the help of some wd40. i would under stand maybe the port side riser being slightly warmer as i replaced this one last year but the starboard side is only brand new replaced on 3 weeks ago. is ther any way of removing the pipe that comes into the thermostat without removing the engine?
ta.
 
When on a garden hose you would be less likely to have flow issues then in the water

garden hose is a supply, in the water the impeller has to suck the water in.

Do not cut any hose or anything else.....

I did not like the flow from the port with no hose in the video.

It should be steady flow and equal or as equal as possible from both ports.

You can connect a clear hose between the rubber one and the T stat housing.

Also the "boot" that sits on top of the water pump housing should be very easy
to push down. No lubricants needed...??????

You do have a alpha 1 gen II outdrive dont you?
 
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I do have an alpha gen 2 outdrive and i only used wd40 to slide down the seal incase i damaged it or ripped it some way on the shaft. It would appear to me the flow in my case would be more of a gulp gulp rather then a steady stream of water. I was putting the weaker flow down to below average water pressure at the tap and i was thinking as the leg would be submerged in water the pump would be able to draw more water in the marina hense better flow to the risers. Just as a precaution i would love to be able to remove the main flow going back to the leg and give it a good clean out but it would appear to be connected to what looks like a mental pipe one side and then snakes quite low behind the engine and out to the leg. I cant get my hands down far enough. what about taking off the hose at the stat housing and blowing backwards with a jet washer or maybe running some kind of cleaning agent through from the mufflers. Their may very well be some kind of obstruction of congealed salt or coral or maybe even rust in that metal pipe creating a bore and narrowing the pipe hense reducing the flow of water. No theres a thought. Since buying this boat back in 2008 i think it has spent most of its life in salt water conditions and i certainly had it in the sea for a all of 08 and most of 09 at my local marina so i dont really know if its was regularly flushed, i kinda doubting it was as the last owner was quite elderly and its quite a large boat to get in and out of the water. maybe it is the metal pipe thats the problem, wonder can i remove the pipe without lifting the engine ?? My only fear is if the flow is some way obstructed i would run the engine to hot out on the water and roast the exhaust bellows or worse roast the engine and crack the heads. I suppose i could remove the lower casing again and connect a hose pipe directly up the leg and see if the flow inproves. there would not appear to be any sign of wear in the waterpump housing but it just dawned on me what if when the impeller was changed before did somebody but the fins going the wrong way and im after doing the same thing as i just copied the direction from the one i had just removed. Now that would be a more plausable answer as the water intake would be a lot less with the impeller blades going the wrong way!
 
Just a quick question if i replaced the fins on the impeller in the wrong direction and i removed the pipe at the stat, ran the engine forward first checked the flow and then it in reverse, should i see an improvement, sound logical but with boats and me logic seems be out the window
 
Agreed. Impeller turns in one direction and even if you spun it the wrong way before installing the lower unit it would self correct.
The small pipe you describe is not metal it is either plastic or copper.
It can not rust BUT it could collect.

Too many unknowns from here.....

My suggestion would be first to remove entire outdrive, then remove incomming water hose from tstat housing and back flush water from your garden hose. NO SOLVENTS.
compressed air is ok also.

If water flow seems ok reinstall outdrive and remove the lower and backflush again.

We are assuming good garden water pressure.

If all of this seems ok then it may be a outgoing water flow issuse

i forget does it do this in the water?
 
The garden hose test for good water is not what is called for.

You need to submerge the drive in water pull the incoming water hose and then start the boat to confirm good water into the motor.

Then go from there.

Good water coming into the motor the problem is down stream.

Bad water then we know ether the hose is kinked inside the the boat at the fitting that enters the transom or the problem is on the outside of the transom say the fitting that enters the transom on the outside.

Or as ghost says the drive.
 
do the impeller vanes self correct?
omc stringer vanes sure don't- they'll stay flipped the wrong way.

140F - uncomfortable to hang onto -threshold of pain
160F -scalds your hand if you apply pressure
212F - spit will fry
300F - paint discolours

I don't see much about this in any forums, but I found it a major struggle to get that water pipe lined up in the grommet when assembling my GENII alpha... I had every mechanic's mirror and digital camera in there trying to make sure I was lined up... I was getting seriously pissed at it.
I suppose it's possible to catch that seal/grommet with the tube when pushing the lower back on. or maybe it's more self-guiding than I was thinking... I get a bit paranoid when I can't get my head in there to see if things are right
 
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hystat said:
I don't see much about this in any forums, but I found it a major struggle to get that water pipe lined up in the grommet when assembling my GENII alpha... I had every mechanic's mirror and digital camera in there trying to make sure I was lined up... I was getting seriously pissed at it.
I suppose it's possible to catch that seal/grommet with the tube when pushing the lower back on. or maybe it's more self-guiding than I was thinking... I get a bit paranoid when I can't get my head in there to see if things are right
Click to expand...

The reason for this struggle is the copper pipe that connects into the water pump housing and the upper housing SHOULD be in the upper housing only when reassembling. You should only need to guide the copper tubing into the water pump housing's plastic tube. That is the purpose of the plastic tube, a guide.

The rubber grommet in the upper should hold the copper tube in place, if not the grommet should be repalced or the tube may be deformed.

You also may be correct about the soft impeller, I do not see many of these, mostly gen I's. Would be worth checking to be sure!!

Also when installing any merc impeller you turn the vertical shaft CLOCKWISE only when pushing the housing down over it.
 
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many thanks gentlemen you are officially my hero's, the boat has always run up around 170F and in my mind that seems about 20F to hot. I haven't had the boat out on the water since i replaced the impeller, the stat the sender switch and the risers and manifolds. so i hope to do it later this evening after work so ill check in later with a progress report.
Thanks
 
No 170 is not to hot......

It all depends on what your thermostat is,

if it is a 143' then normal idle temp would be ~ 150ish, when running at high speeds 170ish is normal.

if running a 160 degree thermostat then 170 at idle would be normal.....

DO you know what you have?
 
no leave it alone. you boat in saltwater ?

Rust buildup will make it run a tad hotter nothing in the world will stop that.

What you can do is flush it after every use and maybe run salt away or something like that every once and a while.

Good luck you have no problem.

If the motor ever gets around 190 then you know it's time for impeller, risers something.
 
damroc said:
yes i just replace it and i have a 160 degree in it, would it be worth changing it again for a 143
Click to expand...

You should run what the serial number for that motor requires.......your merc dealer should have that info.

For many years the 143 was the standard for non closed cooling systems. Closed cooling (heat exchanger) used a 160.

Not sure what your motor serial number call for.
 
thaks kgost to me it would make sence to have the stat opening earlier to allow the water to flow at a lower tempature, i think i will change it for a lower tempature, this may very well be the problem. slainte.
 
That is not the reason for differences in thermostat ratings in a marine enviroment. It has to do with salt water crystalization at certain temperatures.

USE WHAT IS SPECIFIED FOR YOUR MOTOR. If the serial number for the motor calls for a 143 then yes change it, It may call for a 160. do not just change it to correct an issue without understanding the issue.
 
ok kgost, ill have to locate the engine serial number and go from there, its not written on top of the air filer cover so it must be somewere on the block its a thunderbolt 5.0 any ideas were i might find it
 
Above the starter rivited to the block ( should be) and it should be a metal tag. About 1 inch long

If the boat is all original and the motor or outdrive have not been replaced then the outdrive/transom assembly/motor serial numbers should all be within a few hundred digits.

EX:
AO1345678 motor
AO1345921 Transom
AO1345219 outdrive

the last few diggits will be close (within 1000) and the several first digits should be the same.
 
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just back after a couple of very successful hours on the water and im glad to report all was well, the boat behaved perfectly and all was good. Many thanks for all the past advice and hope everyone has a very safe and enjoyable season 2011. Best wishes.
 
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