Mercury 60 HP Two Stroke Overheating:

Have overheating problems with the engine at idle, the tell tale is very weak. Decided to strip lower unit off, replace impeller, gaskets, o rings and rubber riser tube. Pressure tested for leaks before re assembly, found no leaks. Re fitted lower half. Removed and chcked thermostat, works to specification. Also checked no blockages in engine waterways; via garden hose through riser shaft when lower half was split off, resulting tell tale was very strong.<br /><br />Tested engine in water barel after finishing rebuild. There is no tell tale pulled through at all, don't understand? Tested engine again with muffs on and some hose pressure, tell tale came through but was not sufficiently strong. Re stripped engine, repeated re build got same end results again. I am at a loss, can anyone advise?<br /><br />Engine tell tale had been extreemly strong after engine hits 1,500 rpm, nothing now. However idle tell tail has always been weak?<br /><br />Any help much appreciated as i'm running out of ideas.<br /><br />PS: ignition idle timing checked and is correct at 2 degrees ATDC, as is idle speet of 850 rpm.

Re: Mercury 60 HP Two Stroke Overheating:

Water flows out the tell tale even when the thermostats aren't open, albeit weakly. It takes a little while for it to reach the 143 degree temp required to open the t-stats, at which point the tell tale should be even stronger.<br /><br />Do you have a water pressure gauge? Your poppet could be stuck open.<br /><br />-andy

Re: Mercury 60 HP Two Stroke Overheating:

Hi Andy,<br /><br />My particular model has no poppet valve, have checked the manual. Before I fitted the new impeller the tell tale always showed up immediately in a barrel of water. When the stat opened the tell tale would get slightly stronger. Currently any water that comes out the tell tale is hot to touch and this was not the case before at idle, its even hot when pressurised through the muffs.<br /><br />I have no pressure gauge at all on the engine. <br /><br />Stewart

Re: Mercury 60 HP Two Stroke Overheating:

Have you checked for clogs throughout the water jacket. Blow out the lines with compressed air or water.<br /><br />Is it spitting water out the relief exhaust holes in the rear of the motor, just under the cowling?<br /><br />andy

Re: Mercury 60 HP Two Stroke Overheating:

Hi Andy, <br /><br />Can you advise how I check the water jacket for clogs, do I remove the thermostat and push water through with a hose? Or is it via the tell tale I apply water pressure, or some other manner?<br /><br />Never say any water in the exhaust relief holes (if i'm looking in the right place).<br /><br />At the rear just above the bottom section there is a lot of water comming out when on muffs, as it always has)<br /><br />Stewart

Re: Mercury 60 HP Two Stroke Overheating:

Well at idle speeds water should be coming out the relief ports as there isn't enough water pressure to push it out the exhaust at the prop.<br /><br />As far as declogging, I would pull the hose off the tell tale and flush it that way. <br /><br />What year is your engine by the way?<br /><br />Are you sure you installed the fins of the impeller in a clockwise fashion (looking downward). If everything else checks out, it should be pumping water. I would drop the L/U again and make sure that : a.) the water tubes are aligned and b.) that the impeller is ok.<br /><br />What was the condtion of the housing for the impeller?<br /><br />Perhaps the t-stats aren't opening. Pull'em and test them with some water on the stove and a thermometer.<br /><br /><br />-andy

Re: Mercury 60 HP Two Stroke Overheating:

Hi Andy,<br /><br />Not sure if the fins are in a clockwise direction, I read on on of the bulletin boards that the fins reverse to the correct direction when the engine starts; I will check them again. I am confident the water tube has aligned. <br /><br />The engine is a 2001 model.<br /><br />Will also try the flushing method you recommend at the weekend. <br /><br />Checked the thermostat, its opening at the correct temp.<br /><br />The housing for the impellor is in good condition<br /><br />Will let you know how it goes,<br /><br />Thanks,<br /><br />Stewart

Re: Mercury 60 HP Two Stroke Overheating:

Hi Andy, tried backflushing the engine, water came through the jacket, to the exhaust, thermostat and bottom pick up tubes straight away. I am sure its not a blocgage I have. Tried the engine on muffs, got a strong tell tale. Adjusted the idle timing and the tell tale got considerable weaker, at on stage it disappeared and the engine overheated. Re adjusted idle timing to get tell tale back. Run the engine in a barrel of water. Tell tale was there but very weak. Engine overheated at idle after 2-3 minutes. Tell tale water became progressively hotter. The cooling system is still not producing sufficient water pressure via the impeller. <br /><br />I have to ponder if Mercury have designed the cooling system incorrectly on this model of engine. As there is another bottom end available for the engine with a larger impeller housing / pump / gearbox. I do wonder why ther intorduced this change. Is this part of the problem? Could it be something to do with the ignition timing? Why does it affect the strength of the tell tale.<br /><br /><br />I think I will need to put the engine into a dealer to have a look at it?<br /><br />Regards,<br /><br />Stewart

Re: Mercury 60 HP Two Stroke Overheating:

the strength of the tell tale is dependent on the engine RPM, so if in chaning the timing you increased/decreased the RPMs you would change you tell tale strength as well.<br /><br />Something doesn't sound right, and I can't say I know where to look next. If you have a poppit valve (which you say you don't) the was stuck open, this would surely cause your exact condition. <br /><br />Whats your serial number

Re: Mercury 60 HP Two Stroke Overheating:

Hi Andy,<br /><br />Finally got the outboard fixed. Had to get outboard specialist to look at it. Very unusual problem, took him apprx 5 hrs to find it. The Merc 60 impeller sits on a St St baseplate. This plate is completely solid except for the water intake slot. The plate was removed and we found salt had lifted the plate enough to break the underlying seal. As a result air was being forced from the exhaust chamber under the plate, up into the water intake hole. A mixture of air and water was being pumped. <br /><br />Cleaned the mating surfaces, replaced the lower gasket, baseplate upprt gasket and housing. reassembled the lower leg. Powered up and the tell tale came out like a jet stream.<br /><br />Fixed at last. This is one to watch out for guy's if your impellor is not working!!!! Unusual, though it occasionally happens<br /><br /><br />Woosh.com

Re: Mercury 60 HP Two Stroke Overheating:

Thanks for the update Wooshcom. I've never heard of that, nor would I look for it if I had a cooling problem. So it's another thing to keep in the back of the old brain, however I've made a note of it in my merc manual.<br /><br />-andy

Re: Mercury 60 HP Two Stroke Overheating:

Hi Andy & Stewart,

Thanks for your information on this matter, it is a hard one to pick, but this surely helped me & was fixed!!!

I hope others check this out as it was a headache that would never have ended without this post

Best Regards

Ray