2000 mercury 125 hp 2 stroke Overheating new Thermostat / waterpump / poppet valve diapghram

[Jhanratt]

Not sure if this should be a new thread or a continuation. please forgive my lack of etiquette.

2001 mercury 125 2 stroke is overheating. I limped it home and replaced the impeller (the old one is 6 years old looked like new.) I replaced the thermostat. The old one looked black and crusty but opened in boiling water. I also installed a new poppet valve diaphram. On the advice of the helpful people on this website I attached a hose to the pipe above the water pump. Water flowed freely through the missing thermostat so the water jacket is not plugged.

I test ran it on muffs and the tattle tale was not running really strong but it was running.
Water was running out of the front motor mount as well. Photos attached.

I lake tested it and it ran 5 minutes before the overheat siren went off.
I noticed that the tattle tale ran continuously but water was coming from the front of the leg around the upper mounts.

I am now at home with the gear case off. I put the hose back on the water pipe and it doesn't seem to leak too bad.
I was hoping for a simple o ring or gasket failure at the top of the water pipe but it doesn't look likely.

Any body have any ideas?
Should i pull the power head?
It still seems to run like a top other than the overheating issue. I did the gear case 6 years ago and other than that it is stock original. I've had it for 12 years.

Thanks very much for your help.

Jeff Hanratty

 

[galamb]

It sounds like the seal at the top of the water tube is toasted. In the diagram below you can see that at the top of the water tube there is a little rubber seal (#17) which is held in place, along with the top of the water tube by the little (bracket/clip - whatever you want to call it) #16.

If the seal is shot, the clip let go or the water tube is pulled out that will result in water coming out from where you note, plus it will not supply enough water to properly cool the power head.

It certainly sounds like that is where your issue is. The part that it's attached to is the exhaust plate/tuner. You do need to remove the power head, then pull the plate to get at it.

 

[Jhanratt]

Here is a potential clue. I found this bolt rattling around under the bottom carb. It has been damaged by getting wedged under the gear shift arm. You can see the threads are squished. I can't figure out where this could have come from but it is clearly an engine bolt. I have pulled the oil tank off and checked all of the bolts behind the carbs. I have also checked all of the head bolts and exhaust bolts and I cannot locate the location it is missing from.

I have owned this boat since almost new and I have rebuilt the gear case, done the carbs once, the starter once, and the spark plugs a couple of times. I did have the motor pulled to change the steering cable 10 years ago and I installed hydraulic steering a few years ago. None of these seem likely to result in an extra loose bolt.

I'm stumped by this bolt. It had to come from somewhere.

Second question. What would the power head weigh. I cannot get the boat into my garage (too tall) I am thinking I could use a rope hoist attached to a wood roof truss in my carport. I am guessing two guys could man handle it off but my guess is lining it back up to re install would require more precision.

Advice?

Thank you

 

[Jhanratt]

Last chance for any other advice before I pull the power head off. I built a steel bracket and tied three roof trusses together so I am ready to pull the power head.
I looked up leg from the bottom with the gear case off and tried wiggling the pump tube and it is rock solid.

Do you still think I should pull the power head off or is there anything else to check first?
Thanks.

 

[Jhanratt]

For your consideration, I attached a hose and clamped it to the tube which goes up into the leg. I applied water at and the first thing to leak is the tattle tale. Second thing to leak is two holes drilled in either side of the exhaust. If i apply even more water it flows extensively through the exhaust. and a little comes down the hole which normally contains the driveshaft.

I am thinking if the upper tube seal was leaking it would show up first even before the tattle tale.

I am ready to pull the power head but I don't want to make work for myself.

could a weak poppet spring do anything?

I am going to pull the water pump again and post pics.

Maybe I am missing something you will see right away.

 

[Jhanratt]

Here are photos of the water pump impeller that I installed.
could it be backwards?
i see some fine sand on the lower water pump plate which is interesting because the boat has not been near sand since the water pump was installed.
I did accidentally go through some shallow sand and gravel a few trips back, but it ran fine for a few trips after that.
Could I have ingested sand and caused an issue?

 

[Jhanratt]

No apparent issues with cylinders.
photo of plugs attached.
compression 120 and dead even on all 4. (my gauge reads low) its more likely 140 dead even.

 

[Jhanratt]

tested temperature switch. Closed at 86 celsius. Opens at 78 celsius. Both are within specs according to the manual.
I put ears on the gear case and water flows readily into and out of the gear case. no apparent blockages.

 

[Jhanratt]

SOLVED!!

I am an idiot for missing this!
At least I didn't separate the power head though!

The water pump tube seal was blown out at the pump. The upper half was at the top of the water tube! The water pressure sent it right to the top.
Here are the photos. Don't laugh. I posted it because it might save somebody else some effort if it happens to them.

This is what my water pump seal looked like.



This is what it looks like with with the missing piece put back.



This is what is broken. It should be one piece.


This half was at the top of my water pump tube.



At least it's a cheap and simple fix!!!

 

[johnnygjr]

Procrastination pays off along with troubleshooting,use sealer on water pump housing gaskets both sides OEM type. Impeller will orientate itself after startup. Alittle grease on impeller will help on installation of housing. A dab on drive shaft splines would be nice also. Make sure shift rod works well before installing l/u And i have no idea were that bolt goes,have you found out yet?

 

[Jhanratt]

The extra bolt is still a mystery. I pulled the oil tank and checked all of the bolts on the crankcase seal and reed valves. There is nothing missing. I have the mercury manual and I checked against the bolt tightening diagrams. The exhaust plate and head are easy to see. There are no missing bolts on my engine. There are two bolt holes on the starboard side of the engine casting which are the right thread but they don't appear to have ever been used. I am writing it off because I can't figure it out.

I can only guess that either the mechanic who pulled the outboard off to install the steering cable or a mechanic prior to me buying the boat dropped it down in there and replaced it with another black painted mercury bolt. It is also possible that I dropped it in there and replaced it with a used bolt and just forgot.

I am guessing it has been there for a long time due to the damaged threads and bolt head from being trapped by the shift lever.

Thank you all.
I very much appreciate the advice.