lakelad Posted August 16, 2020 Share Posted August 16, 2020 Hi All, I'm after some tips from the community as my Mercury 2001 3cyl 50hp outboard is overheating when in neutral? Interestingly it does not overheat when on the hose at home (more water pressure I assume), or when moving along, it only gets hot when idling in neutral. Water appears to be coming out fine from the outboard, as long as I don't sit for 30 secs at idle it still runs well have done many miles in it since noticing this. Now I've recently done a service, so either I buggered something up or this is coincidental timing.. service involved new impeller, gearbox oil, spark plugs, thermostat/gasket. Have tested old and new thermostats in hot water, both seem to work OK. Impeller looks the same size as the last one and fits OK also. Googling has led me to "poppet valve" related issues these symptoms, but those appear to be with larger engines, I'm not sure my 50hp has a poppet valve? My pdf service manual doesn't mention anything related to a this. Any tips?? Link to comment Share on other sites More sharing options...
kingie chaser Posted August 16, 2020 Share Posted August 16, 2020 (edited) Whats the pressure/flow like coming from the telltale at idle? When you changed the impeller did you just change the blade or did you fit a whole kit including the gasket?? The thermostat also sounds like it could possibly be the incorrect temp rating, was it an OEM part? Edited August 16, 2020 by kingie chaser 1 Link to comment Share on other sites More sharing options...
noelm Posted August 16, 2020 Share Posted August 16, 2020 Check the poppet valve, or pressure relief valve, or whatever Mercury call it, that's it's function. 1 Link to comment Share on other sites More sharing options...
kingie chaser Posted August 16, 2020 Share Posted August 16, 2020 (edited) 17 minutes ago, noelm said: Check the poppet valve, or pressure relief valve, or whatever Mercury call it, that's it's function. I noticed on a youtube I just watched that the gasket on the for the thermostat housing needs to go under the thermostat but over the top of the poppet diaphragm. Is that how you installed it @lakelad? Edited August 16, 2020 by kingie chaser 1 Link to comment Share on other sites More sharing options...
lakelad Posted August 16, 2020 Author Share Posted August 16, 2020 (edited) Thanks for the trouble shooting tips guys, here are my answers to the questions: 2 hours ago, kingie chaser said: Whats the pressure/flow like coming from the telltale at idle? It seems OK, not dribbling but running solid, not racing like under full steam. 2 hours ago, kingie chaser said: When you changed the impeller did you just change the blade or did you fit a whole kit including the gasket?? I bought this kit: https://www.outboardspares.com.au/ossk32o Mercury Mariner 50-60hp 2 Stroke Service Kit with Oils (OSSK32O) The thermostat has the same markings as the old one which worked OK, and they both functioned OK when I put then in a pan of water and heated it up so I think this is OK. New one opened slightly earlier and a bit further but that would make the engine cooler right? 2 hours ago, noelm said: Check the poppet valve, or pressure relief valve, or whatever Mercury call it, that's it's function. I can't fin a poppet valve Noel (50hp 2001 3cyl Mercury 2 stroke), I'd be happy if the motor had one I could service, but not sure it has one? 2 hours ago, kingie chaser said: I noticed on a youtube I just watched that the gasket on the for the thermostat housing needs to go under the thermostat but over the top of the poppet diaphragm. Not sure I have a poppet valve on the 50hp mate? I will take some photos of the gasket and thermostat with cover off and post here.. Edited August 16, 2020 by lakelad Link to comment Share on other sites More sharing options...
kingie chaser Posted August 16, 2020 Share Posted August 16, 2020 (edited) 1 hour ago, lakelad said: Not sure I have a poppet valve on the 50hp mate? I will take some photos of the gasket and thermostat with cover off and post here.. Yeh I think they use one in higher HP Mercs. What is the actual model anyway?? I would think if you have good telltale flow that maybe the thermostat is not opening at the correct temp? The one you bought looks like the right temp @110*F which is what Merc recommends. When you say its over heating what gives you the idea it is & what is it actually doing?? Edited August 16, 2020 by kingie chaser Link to comment Share on other sites More sharing options...
Smobaby Posted August 16, 2020 Share Posted August 16, 2020 Check to make sure that the inlet tube is correctly inserted into the rubber grommet on the impeller housing sometimes they misalign tear the rubber then at idle you will only get limited water flow at speed this will be better but not 100%. 2 Link to comment Share on other sites More sharing options...
zmk1962 Posted August 16, 2020 Share Posted August 16, 2020 26 minutes ago, Smobaby said: Check to make sure that the inlet tube is correctly inserted into the rubber grommet on the impeller housing sometimes they misalign tear the rubber then at idle you will only get limited water flow at speed this will be better but not 100%. I was about to suggest exact same. Especially if the problem only surfaced after you worked on the impeller. cheers Zoran 1 Link to comment Share on other sites More sharing options...
kingie chaser Posted August 16, 2020 Share Posted August 16, 2020 (edited) 5 hours ago, kingie chaser said: Whats the pressure/flow like coming from the telltale at idle? The question was asked & you can only go off the info provided 2 hours ago, lakelad said: It seems OK, not dribbling but running solid, not racing like under full steam.. Edited August 16, 2020 by kingie chaser Link to comment Share on other sites More sharing options...
lakelad Posted August 24, 2020 Author Share Posted August 24, 2020 (edited) On 8/16/2020 at 6:34 PM, Smobaby said: Check to make sure that the inlet tube is correctly inserted into the rubber grommet on the impeller housing sometimes they misalign tear the rubber then at idle you will only get limited water flow at speed this will be better but not 100%. Thanks @Smobaby and @Zoran, I haven't managed to get back on the water as yet, but I did pull the leg off on the weekend and review the impeller, not sure I have the rubber grommet you refer to though, see photos below? Since I had a spare new impeller and was clutching at straws I replaced it as well as the two rubber washer/bushing which I had not replaced with the previous impeller. Only thing worth noting is the slightly used impeller (2 half day trips) has a slightly roughed edges as per the photo, will see how it goes now when I get a chance to hit the water. I put some silicon grease on all the rubber also this time. Edited September 14, 2020 by lakelad Link to comment Share on other sites More sharing options...
lakelad Posted August 24, 2020 Author Share Posted August 24, 2020 On 8/16/2020 at 7:15 PM, kingie chaser said: Whats the pressure/flow like coming from the telltale at idle? If it's overheating next trip I'll review and take a video for advice on the telltale. Link to comment Share on other sites More sharing options...
wrxhoon1 Posted August 24, 2020 Share Posted August 24, 2020 Are you sure you installed the impeller correct? Looking at the blades one of them ( the one at 7 o'clock in the pic) looks like is bent the wrong way. When you put the new one in make sure you bent them the opposite to the shaft rotation . You can check at home if she overheats, all you do is run it in a drum, saves launching just to check overheating. 1 Link to comment Share on other sites More sharing options...
Fun2fish Posted August 24, 2020 Share Posted August 24, 2020 Are you getting steam from relief vents had that with my motor was a blown head gasket. I'm trying to see about a fix for small hole in block where gasket blew but saying that motor running fine just the steam at idle a concern 1 Link to comment Share on other sites More sharing options...
kingie chaser Posted August 24, 2020 Share Posted August 24, 2020 On 8/16/2020 at 6:11 PM, kingie chaser said: When you say its over heating what gives you the idea it is & what is it actually doing?? You still havent described the symptoms of your over heating???????????????????????????????????????????????? Link to comment Share on other sites More sharing options...
noelm Posted August 24, 2020 Share Posted August 24, 2020 Did you replace the entire pump kit, including the wear plate and housing, or just the impeller, and did you use genuine parts, or after market copies? 1 Link to comment Share on other sites More sharing options...
kingie chaser Posted August 24, 2020 Share Posted August 24, 2020 3 minutes ago, noelm said: Did you replace the entire pump kit, including the wear plate and housing, or just the impeller, and did you use genuine parts, or after market copies? Question was asked on post #2 1 Link to comment Share on other sites More sharing options...
noelm Posted August 24, 2020 Share Posted August 24, 2020 Didn't see that, the wear plate looks pretty bad/worn, that's why I asked 1 Link to comment Share on other sites More sharing options...
Fun2fish Posted August 24, 2020 Share Posted August 24, 2020 I know you should make sure impeller is installed on proper direction but wouldn't rotation place blades correctly if you bugger it up 1 Link to comment Share on other sites More sharing options...
Greg Foster Posted August 25, 2020 Share Posted August 25, 2020 Hi lakelad my old 35 Johnson overheated after a service took it back to thomos at Gateshead was really hot when I lifted the leg up to winch it on the trailer no tilt on the old girl to old 😂 He ended up taking the thermostat out, Apparently there not really needed unless your in really cold water Lake Macquarie is not that cold Well worth a talk to he may help 1 Link to comment Share on other sites More sharing options...
noelm Posted August 25, 2020 Share Posted August 25, 2020 Never take the thermostat out, buy a new one and replace it, they are there for a very good reason, but "old time" mechanics take them out, just like they remove the auto oil systems. 2 Link to comment Share on other sites More sharing options...
lakelad Posted September 14, 2020 Author Share Posted September 14, 2020 Thanks for all the advice here guys, some great tips which I hope help the next guy. I resolved my issue in the weekend, I looked over everything previously posted and replaced the wear plate and rubber pickup tube. The old pickup tube was on the engine side, and I think it may not have been lined up exactly with the pickup from the water pump housing. To clear up the questions above, regarding overheating the engine was getting warmer every second in idle going from running temp at 30% on the gauge slowly over 45 seconds to 100% of the gauge. This video put me onto the pickup tube, good for anyone with a similar motor, I notice a lot of these old Mercury's still going out there: Link to comment Share on other sites More sharing options...
Hoods Posted September 14, 2020 Share Posted September 14, 2020 Only other issue I can think of is the rubber grommet at the head plate may have swollen & closed up a bit which is a common issue with the Merc's - thanfully mine is still ok as its a bit of a job. Local Merc mechanic advised to fix garden hose tot he water pipe in the leg & see if it comes out the tell tale Ok or if there is a problem it will blow the garden hose off indicating an issue between the water pipe & the housing (ie the grommet). I found a youtube on changing the grommet - just search. Hoods Link to comment Share on other sites More sharing options...
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