Is it Hot or Not

[ksuydam]

Ran my 77 Merc 50 today and the water out the weep hole was extremly hot but I could hug the block if I wanted, I touched the head around each sparkplug and it was all cool to the touch,<br />I really don't know if there is a thermostat install, but I think not.<br />I also don't know if there is a heat alarm or if it's been disconnected because it never went off.<br /> It took maybe 10 minutes for the water to get that hot. <br />I also noticed that there was lets say, exhaust type smoke coming from around the power pack, I think it maybe from that little tube that runs along the backside of it.<br />Could that maybe perhaps heating the hose to the weep hole causing the water to appear hot?<br />The whole water pump is only 6 months old and it was installed correctly.

 

[Barnacle_Bill]

Re: Is it Hot or Not

If the head feels cool to the touch, it definitely isn't running hot. You should be using a thermostat so the motor can run more efficiently. I would investigate that smoke.

 

[emckelvy]

Re: Is it Hot or Not

Are you sure it's smoke, or steam? The water out of the pea-hole should not be hot at all, at the most lukewarm.<br /><br />This motor has no thermostat. Feel the exhaust cover when the motor has been running for 5 minutes or so, if it's very warm you've got poor water circulation thru the block. The water is picking up excess heat because there's not enough flow.<br /><br />Most common cause of this problem is silted-up block or broken impeller blades in the water supply tube.<br /><br />You can remove the cylinder block cover (the back plate over the spark plugs) to reveal the tops of the cylinders which are integrally cast into the block (this motor has no head per se). There may be a lot of silt or debris built up in the passages around the cylinders, you'll need to clean this all out by mechanical means, water flushing, maybe compressed air. Remove the lower unit and provide water from your garden hose to the water supply tube. You should get a strong flow out the tube up into the back of the block, this'll flush any remaining debris out.<br /><br />Note that the 1/4" bolts holding the back cover on are very prone to snapping off, if you encounter any more than a moderate resistance when you remove them, you must apply heat (use a propane torch). If you snap any, you'll have to drill them out or drive them out (depends on whether you have thru-bolts or tapped holes in the block).<br /><br />If you bust any of the lower bolts, you'll have to remove the powerhead to gain access to them.<br /><br />HTH and Good Luck.........ed

 

[andrewkafp]

Re: Is it Hot or Not

The telltale on a 50hp 4 cyl when idling will only be lukewarm. You don't say when it is "Hot". If you run it hard for 10 minutes, then anchor, it will be quite warm to hot, but should go back to warm after 30-60 seconds.

 

[ksuydam]

Re: Is it Hot or Not

The water is super hot when running, but like I stated I can touch the block anywhere and it is cool to just warm to the touch. You can't hold your hand long from the water coming out the telltale(p-hole).<br />It really is a puzzle. 3 weeks ago it was not a problem. Just a thought here, Could those pesky little black wasps that make nests in any hole they find made a nest deep inside and blocking water flow?

 

[TELMANMN]

Re: Is it Hot or Not

I picked up a infrared thermometer from gander mountain last fall on clearance. I am sure other sporting good stores around the country also handle them. <br /> My "pee hole" seemed to always quit, but the motor never gave an alarm it was over heating. I wuold then bring the motor up, let it drain and the majority of the time, if when restarted, it would start spitting. <br /> I picked this up and took head temps and it was always cool(around 110) so I then got a small wire and ran it up the pee hole and it cleared. <br /> Now this is on a 50 hp. 2003 Merc.(also on my 98 40hp merc on my pontoon) which I run on my lake which has a very weedy frontage. I had always figured the tell tale was getting pulgged but was always leary about running the motors too much with out verification that the temp. was ok.<br /> Once I got the infared temp. gauge I took the head reading and figured it had to be plugged in the inlet so then ran the wire up(picked up a stainless role of wire approx. 20 gauge and just run it up for 2 feet etc. <br /> Apparenty I took something out as now I am having no problems.

 

[andrewkafp]

Re: Is it Hot or Not

ksuydam.<br />Do you have a pressure gauge connected ? A 4cyl 50 waterpump should be pumping around 6psi at @5000 and around 2-3 at 2000-3000.<br />The water is too hot if you can't touch it. With my 1980 50 ruuning near WOT (Another driver) I can hold my hand under to pee'er indefinately. The W/P is a few seasons old, and is in need of replacement soon.

 

[ksuydam]

Re: Is it Hot or Not

No I don't have a pressure gauge and my water pump is only 3 maybe 5 months old. I replaced the whole pump instead of just the impeller to avoid this situation. I had the exhaust plate or whatever it is on the left side replaced when water was seeping into the plugs. The mechanic told me he had flushed the whole system because of build up he had noticed. I also flushed around and scraped all the build up under the water pump. The water coming out the p-hole is strong and when you accelerate it gets even stronger, which tells me that there just can't be a blockage, but I had problems with little black wasps making nests inside the p hole tube.<br />Could they somehow blocked a 1 or more water ports but is still allowing the water to be by passed thru others?<br />The cylinder heads are definetly not getting hot.<br />You can leave your hand on the heads or any other part as long as you want. But You cannot put your hand under the stream of the p-hole long. It is like something is super heating the water on its way out.<br />Or could this have something to do with the problem.... I recently had to replace the hub in my prop, It was really corroded on and I dang near had to beat the thing to death to get it off, with a puller and heat of course. Could this have damaged the water pump? I just noticed today that I must have damaged the seal cause its leaking oil now, but the bearing seems to be ok, no play in shaft.

 

[andrewkafp]

Re: Is it Hot or Not

Dunno what to tell you ksuydam.. If you have good pressure and flow, but the water is hot. That is not like my 1980 50, and your 77 is virtually the same as mine. A blockage would most likely reduce the flow, and a lean condition would make at least part of the motor very hot. Keep posting, as there are far more qualified Mercsters than I on here. Lucky you are observant and spotted it quickly, before any damage. You may wanna look at the plugs for any abnormal burning or aluminium. You can tell a lot from the plugs. I have found 12footer, Kclost and our own.. Achris to be quite competent on Mercs and may have some answers.