kiro Posted June 13, 2008 Share Posted June 13, 2008 Hey raiders, I should probably be banned from this site for my stupidity... I took my boat out during the long weekend (i have a reconditioned johnson 50) and i have 2 22ltr fuel tanks... in the spare tank, i filled it with unleaded, AND FORGOT TO MIX IT WITH OIL... i was boating for about 1 1/2 hours from the tank with no oil... is my motor screwed???? i flushed it when i got home (added the oil then), and it started ok.. i left it running for a bit... how bad do u think i damaged it??? help! Link to comment Share on other sites More sharing options...
chrisg Posted June 14, 2008 Share Posted June 14, 2008 Hey raiders, I should probably be banned from this site for my stupidity... I took my boat out during the long weekend (i have a reconditioned johnson 50) and i have 2 22ltr fuel tanks... in the spare tank, i filled it with unleaded, AND FORGOT TO MIX IT WITH OIL... i was boating for about 1 1/2 hours from the tank with no oil... is my motor screwed???? i flushed it when i got home (added the oil then), and it started ok.. i left it running for a bit... how bad do u think i damaged it??? help! Doh.....First thing to do is get the motor compressions tested. That will give you an idea of any damage caused. The fact that it didn't seize is good..you may have got away with the very worst. Get it checked first then worry Chris Link to comment Share on other sites More sharing options...
a boat Posted June 14, 2008 Share Posted June 14, 2008 Hi, I agree with Chris, do a compression check and see what the results are-both cylinders should be equal. If OK you will be lucky because if it was running for 1.5 hours on the plane then I would be guessing that you have caused problems-Imagine running anything without lubricating oil, but at least with the 2-Stroke design you have they run needle roller bearings which can cope better without oil than slipper bearings, but the problem will be the lack of oil in the combustion chamber and damage to the pistons and bore. Let us know what you find when do a compression test. Cheers, Huey. Link to comment Share on other sites More sharing options...
Dreamtime Posted June 14, 2008 Share Posted June 14, 2008 Hey raiders, I should probably be banned from this site for my stupidity... I took my boat out during the long weekend (i have a reconditioned johnson 50) and i have 2 22ltr fuel tanks... in the spare tank, i filled it with unleaded, AND FORGOT TO MIX IT WITH OIL... i was boating for about 1 1/2 hours from the tank with no oil... is my motor screwed???? i flushed it when i got home (added the oil then), and it started ok.. i left it running for a bit... how bad do u think i damaged it??? help! Your engine must have teflon liners to last that long without oil and not seizing! Unless the rings are "R.S" and other oils are lubricating your pistons. Your call Huey???? Link to comment Share on other sites More sharing options...
pelican Posted June 14, 2008 Share Posted June 14, 2008 It's a good sign it is running and you didn't mention odd noises or lackof power. I've seen a few survive terrible lack of oil abuse and it depends on what load and revs they did for that hour and a half. Older motors sometimes ran real cool without thermostats and there would be a pool of oil in the crankcase. Poor quality oils often pooled as well at low revs. A lot of old outboard tanks have a sediment of old oil in them and every little bit helps if some of it disolved into solution. Test it and see what you've got as a compression test will give you some idea of how hot it got and whether the bores are scored or have metal transfer. Did you know the compression readings after it got rebuilt? If you did you would have a very accurate comparison. Do you know if it was a full rebuild?? Cheers PS. Your other motor not sure I understand just what your "mechanic"has described as the problem?? Link to comment Share on other sites More sharing options...
kiro Posted June 14, 2008 Author Share Posted June 14, 2008 Thanks heaps for all your help and suggestions guys... its much appreciated.... the support on this site is remarkable.!! I got the compression readings, and the bloke said it was 140 equal?? he said thats a good thing... i wouldnt have a clue what that means... the other motor (chrysler 30hp), the bloke said the bottom piston has problems... when i took it to him, i told him that when i was out with it, it kept bunny hopping on the water... it would go go go and then retreat, then go go again, then retreat (didnt retreat much, but still...) He said that because of the bottom piston, sometimes not enough fuel gets to the motor, thats why it retreats... it still starts and runs no problem, but it bunny hops from time to time... has what he said made any sense?? my problem is i dont know a thing about boats, or motors.... i just love fishing, and been fishing my whole life (land based)... and if having a boat is going to increase my chances of catching fish, then i have to have a boat! a few weeks ago, i bought a 4.5m sportsman craft.. beautiful looking boat... (i'll post some fotos soon).. once again, thats for all your help raiders... i'll keep yous posted when i get the boat back... in peace, Kiro Link to comment Share on other sites More sharing options...
pelican Posted June 14, 2008 Share Posted June 14, 2008 Equal is good and 140 is good Link to comment Share on other sites More sharing options...
Robbielites Posted June 14, 2008 Share Posted June 14, 2008 On the subject of compression.... Is there an acceptable limit with compression loss? I.e at what stage do you worry? Say you have a twin cylinder motor and factory spec is 150 but both are at 135 so I have lost 10% do you panic or is a variant between cylinders say 150 the other 135 more detrimental than both being down equally? Robbie. Link to comment Share on other sites More sharing options...
jewgaffer Posted June 14, 2008 Share Posted June 14, 2008 Say you have a twin cylinder motor and factory spec is 150 but both are at 135 so I have lost 10% do you panic or is a variant between cylinders say 150 the other 135 more detrimental than both being down equally? Robbie. That's a good point Robbielites. They used to test out the performance of Fords, Holdens and Valiants as taxi cabs particularly in the competion for taxi cab new vehicle business, in the sixties and the early seventies. The Valiants had very smooth engines and had very even compression , the Holdens were also smooth and even. but the one that lasted over a million miles as a taxi was the the Ford XT, XW, XY, XA, XB, and later the XC which remained current for a number of years (most taxis did over 100,000 miles a year in those days due to less traffic). The relevance is that the Fords all sounded as rough as guts in idling with the compression all over the place with a lot of difference in each cylinder when measured, whereas the other two motors were as smooth as silk but the engines had nowhere near the trouble free performance or life span of the Fords, which had a distinct uneven sound. I'm not sure if uneven compression in boat motors could tell the same story. The replies will be interesting when people with a couple of experiences with uneven boat motor compression with the same or better or a loss in performance inside the 10 per cent or behond add to the discussions in regards to the affect on boat engine life as well. Cheers jewgaffer Link to comment Share on other sites More sharing options...
IWANNABROCK Posted June 14, 2008 Share Posted June 14, 2008 It is more important that all cylinder's have the same compression with in 10 psi of each other,that was what I was taught as an apprentice. Link to comment Share on other sites More sharing options...
a boat Posted June 15, 2008 Share Posted June 15, 2008 Hi Kiro, if the compression is 140 on each cylinder than you are lucky because that is fine and being equal is the most important thing, or at least with the acceptable 10% variance. If the guy is trained he could do a leak down test also, which can determine the condition of the rings, but a compression check is more common. Also if you trust the guy, I would get him to remove the cylinder head and visually inspect the bores because running for the time you did without oil is not good and as mentioned at the same time replace the head gasket, which is a preventative maintance measure also, and just make sure you run a 50:1 mix from now on and that the thermostat is installed and operating correctly. As for what is acceptable, there is nothing as a STD compression reading because different engines have differnt compression ratios and there are no factory specs for compression, the important thing is that they are even. Of course if compression was below about 80 PSI on each cylinder than that would be a worry and require looking into. Older carby 2-Strokes like to be "power tuned" from time to time and this will chemically clean the ring grooves of carbon and can bring back compression, but more importantly can help stop the engine failing due to not being able to dissapate the heat from the piston, thru the rings into the block, which can cause the pistons to become too big and seize. Also running good quality oil will help with carbon build-up and the modern synethic oils like XD-50/XD-100 actually have an addative that stops carbon build-up. Cheers, Huey. Link to comment Share on other sites More sharing options...
Flightmanager Posted June 15, 2008 Share Posted June 15, 2008 It doesnt sound like he was running neat petrol , there must have been some old fuel/oil mix in the tank when he topped it up !! OK , probably running at 200:1 , but enough not to shred the engine !! Ross Link to comment Share on other sites More sharing options...
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