explanation sought!!!

[rxl123]

I just don't get this, right. I have 70hp '83 evinrude. <br /><br />I premix the oil to the right quantities 50:1 in new fuel (both tanks). All spark plugs are in the same condition.<br /><br />But it smokes - and I mean quite a lot. It smokes on idle, and if I throttle up in neutral I get clouds of bluey smoke, and the occasional sneeze.<br /><br />I think it runs lumpy (but I haven't heard another to compare), and it stalls when engaging a gear.<br /><br />I can't believe that all three carbs are playing up at the same time, as evidencd by the identical spark plugs. Therefore I'm assuming this is not a carb problem, particularly as neither jets or mixture ( I believe) are adjustable.<br /><br />What else can cause smoke, or MUST it be the mixture in the can? I'm new to this boating lark, and while I think I'm doing it right, I may be missing something.<br /><br />Please guys - give me a steer here!

 

[Jkurtz29]

Re: explanation sought!!!

Do you have the right plugs going to the right spot?

 

[rxl123]

Re: explanation sought!!!

Hey JKURTZ,<br /><br />The plugs are new and from a OMC dealer declared as correct. <br /><br />Don't understand what you mean by 'going to the right spot?

 

[ob]

Re: explanation sought!!!

rxl123,There are several factors that can effect the performance of your engine.Your symptom off hand to me sounds like you may have some failed reeds.Insure that all of the fixed orifices in your carbs are clean and clear of any restrictions.Run a compression test on the engine and post the results and we can go from there.You'll also need to confirm the link and synch of your carburetor linkage.

 

[oldboat1]

Re: explanation sought!!!

Look for simple things first. First insure that the motor is pumping plenty of water -- can't tell you if that motor has a tell-tale or exhausts water from a port in the leg, but you need to see water somewhere. If you are not pumping water, handle that problem first -- may find it's related to (or a cause of) the other problems.

 

[Dhadley]

Re: explanation sought!!!

Lets start at the begining. Is this motor new to you? If not, has it always done this? Has it sat for a while -- if so, how long? What spark plugs are you using? (We need the actual number on the plug) What brand oil? Describe how you measure 50:1.<br /><br />If this motor is new to you, clean the carbs and install new kits. <br /><br />Let us know!

 

[moderator1]

Re: explanation sought!!!

rxl123,<br /><br /> I am combining your posts. They ask the same question. Following is your first post and responses. <br /><br />Hi,<br /><br />I have 'too much smoke' on my evinrude 70 1983 coming out the prop. Its blue-ish initially and then becomes slightly less blue. Also get some coming out the 'nostrils' at water level, but this could be steam. Tell tale is cool, but thermostat housing is hot enough to make me think twice about putting a finger on it.<br /><br />If steam, what does this mean? <br /><br />If oily smoke in a non VRO what can cause this if the mixture is OK?<br /><br />Thanks <br />--------------------------------------------------------------------------------<br />Posts: 7 | From: Wiltshire, UK | Registered: Aug 2003 | IP: Logged <br /> <br />rxl123 <br />First Mate <br />Member # 30518 <br /><br /> posted August 21, 2003 06:13 AM <br />--------------------------------------------------------------------------------<br />Also, put new plugs in - had a look and are 'wet and black' not dry and brown.<br /><br />Thanks - help appreciated<br /><br />Gary <br />--------------------------------------------------------------------------------<br />Posts: 7 | From: Wiltshire, UK | Registered: Aug 2003 | IP: Logged <br /> <br />The Marine Doctor <br />Captain <br />Member # 29197 <br /><br /> posted August 21, 2003 09:07 AM <br />--------------------------------------------------------------------------------<br />The engine is running rich.<br /><br />No harm in replacing a thermostat...just in case.<br /><br />TMD <br />--------------------------------------------------------------------------------<br />Posts: 569 | From: SK Canada | Registered: Jul 2003 | IP: Logged <br /> <br />rxl123 <br />First Mate <br />Member # 30518 <br /><br /> posted August 21, 2003 01:58 PM <br />--------------------------------------------------------------------------------<br />Tks Marine Doctor - however I don't quite get you. <br /><br />You suggest replacing a thermostat but the only thermostat I know is the water cooling thermostat. I've got a manual but I can't find any others.<br /><br />Can you expand a little please so I can follow?<br /><br />Ran the boat up in the tank today - it runs a bit lumpy, smokes all the time, particularly under some revs, sneezes occasionally, and when idling in neutral stalls if I select a gear.<br /><br />Any suggestions other than throw it away? I've got new leads new plugs new pump new fuel hose, even appearance on all spark plugs and I'm running out of ideas. Compression is 140, 137, 133<br />Thanks a lot<br /><br />Gary <br />--------------------------------------------------------------------------------<br />Posts: 7 | From: Wiltshire, UK | Registered: Aug 2003 | IP: Logged <br /> <br />2K BOAT <br />Captain <br />Member # 5118 <br /><br /> posted August 21, 2003 03:34 PM <br />--------------------------------------------------------------------------------<br />mite need to rebuild carbs. <br />--------------------------------------------------------------------------------<br />Posts: 608 | From: charleston, sc | Registered: Nov 2001 | IP: Logged <br /> <br />The Marine Doctor <br />Captain <br />Member # 29197 <br /><br /> posted August 21, 2003 04:08 PM <br />--------------------------------------------------------------------------------<br />The carbs are delivering to much fuel.<br /><br />Remove them and clean and rebuild them.

 

[rxl123]

Re: explanation sought!!!

tks for the responses guys. I seem to have invoked the moderator - I've never used this before and am sorry if two threads has mucked you about.<br /><br />To answer the questions:<br /><br />Compression test delivered 140, 137, 133. Set the throttle linkage as per the manual. Haven't been under the flywheel to do the timing stuff as have neither light or piston stop.<br /><br />I measured my oil by puting in 15 litres of fuel and 300 mil of oil. Used motorbike 2 stroke (wont do this again), however it still smokes at about the same rate on my second tank - which is still full from the previous owner.<br /><br />Tell tale is piddling nicely.<br /><br />Motor is new to me, and no it hasn't always done this. Initially got major power loss no smoke tho' - a couple of times up and down the lake and I couldn't get on the plane in 14 ft fletcher! Leads and plugs were shot, throttle butterfly centre carb was loose,bulb was bulging not squeezing. Runs better now but now started to smoke, sneezes when I give it throttle in neutral, stalls when I engage drive and still feels a bit lumpy.<br /><br />I partially stripped one of the carbs, but the float was clean, and it all looked fine, and so I assumed that as the spark plugs all looked the same the carbs must all be in about the same cond.<br /><br />However from what you guys are saying - the carbs do sound like a favourite. I'll have a go at all of them. I don't have a special tool for removing bits - do I need one?<br /><br />And finally, OB - you mentioned reeds. I am guessing this means the jets in my language? If not can you clarify?

 

[OBJ]

Re: explanation sought!!!

Hi rxl...<br /><br />What ob is refering to are the reed cages that set in the engine right in back of the carbs. When you take off a carb, look in the hole and you will see them. They act as one way valves. They let fuel/air mix from the carb enter the engine but won't (should not) let the the pressure from the piston downstroke blow out the carb. Bad reeds can sometimes be identified by "blow back" from the carb throats. This will be a puffing from the carb throats usually noticed at idle. You will also notice what appears to be (and is) a lot of fuel laying in the carb cover or around the front part of the lower engine pan. Damaged reeds will cause a rough idle as the cylinders aren't getting the fuel/air mix needed. <br /><br />With the motor at idle, you can hold a piece of light toilet tissue, just a strip, in front of the carb throat. It should want to suck in. If it blows out, then your reeds for that carb are probably damaged.<br /><br />One question, have you had any bad backfires or hard "sneezes or coughs" from the engine lately?<br /><br />Keep us posted and Thanks.

 

[rxl123]

Re: explanation sought!!!

Outboard Jim,<br /><br />Tks for the info on reeds. I'll give the tissue strip a go - sounds like a good test.<br /><br />Yes I have had hard sneezes, particularly if I rev up in neutral (haven't tried in gear as am in test tank), and this co-incides with a lot of smoke.<br /><br />rxl123

 

[ob]

Re: explanation sought!!!

rxl123,might want to use something like a dollar bill to perform the blowback test to avoid a piece of the tissue material from being injested into carb throat.Should detect intermittent suction but no blow back.Good luck.

 

[OBJ]

Re: explanation sought!!!

A dollar bill?? I'll give that one a try ob. Thanks.

 

[Solittle]

Re: explanation sought!!!

Lets look at what you wrote:<br /><br />"I measured my oil by puting in 15 litres of fuel and 300 mil of oil. Used motorbike 2 stroke (wont do this again), however it still smokes at about the same rate on my second tank - which is still full from the previous owner."<br /><br />So you have one tank with the wrong oil in it and the other has gas from the previous owner and you probably don't know how old that gas is or wht kind/how much oil the owner put in it. Seems to me you need to dump all of the questionable fuel from both tanks, purge all the lines and start with fresh. Go from there and if need be:<br /><br /> http://www.outboardrepairs.com/carburetors/

 

[ob]

Re: explanation sought!!!

Ditto on that SoLittle.

 

[OBJ]

Re: explanation sought!!!

Yep...me to "Ditto".<br /><br />rxl....if it's sneezing hard, it may be due to one or more of the low speed needles being adjust to a "to lean" condition. This is not a desirable situation. How 'bout doing this....on each carb, count the number of turns it takes to lightly seat each needle and let us know what you find. If it's a half turn or less, the needles are to lean.<br /><br />Hope ob or someone is looking at this to keep me straight here....<br /><br />Lightly seat, and I mean lightly, each needle and back out 1 1/2 turns. Start the engine and let it come up to operating temp.<br /><br />Start with the top needle and turn it in 1/8 turn until the engine starts to get "sloppy". Make a mark where this occured. Now go the other way. When you find the place where it gets sloppy, make a mark there and move the needle midway between the marks. Do this with all the carbs. May take awhile. Allow 15 sec. between adjustments for it to take effect.<br /><br />I think I 'splained that right.

 

[ob]

Re: explanation sought!!!

OBJ,I'm racking my brain here and can't for the life of me remember whether the 83' 70 hp had adjustable mix screws or fixed orifices.My 85' were all fixed.If it does have the mix screws your procedure is fine.I've found that the ones I've run like to be open around 3 turns.I think he'll be on the right track givin the history of the engine and the fact that one of the carb flaps was loose to give all three carbs a complete rebuild.

 

[OBJ]

Re: explanation sought!!!

ob....rechecked the parts book and seems they went both ways. They show a needle and also a fixed jet and screw plug for the same place. Have to check the regular book when I get to the shop. Probably a mid season change from needle to fixed jet although both models for that year show he same thing as I explained above. Dang things....why can't it be simple all the time....LOL.

 

[rxl123]

Re: explanation sought!!!

Tks for this stuff guys.<br /><br />OK - I like the dollar bill trick - thanks.<br /><br />On the oil - I take your point and I will do a flush. Reading around this forum I can see how big a deal it is - I'm not used to it being this critical in my car! However I did discount oil on the grounds that the same fuel in the same tank before I replaced leads sparks bulbs etc DID NOT smoke. Saying that, I got roughly 40% power loss after 10 mins but no smoke! Haven't been able to assess this power loss since replacing the bits - on the lake on Monday and will know more then.<br /><br />On the carb rebuild - I had kind of discounted that on the grounds that before I replaced all the sparks the build and state of all the plugs was identical. I took apart the top carb and the float and hinges and stuff were in A1 condition. I therefore reasoned that if that looked OK - and the plugs were evenly coloured up they all were OK. I guess that the new plugs haven't been in long enough to show any state other than new, and as the smoke is new it may be that one of the carbs has gone offline. <br /><br />What do you reckon to running the engine, and taking out the HT lead of each cyl in turn to see if the smoke goes away - that should highlight if the problem is specific to a cylinder as without combustion, no smoke right?<br /><br />Mind you, I do take that a carb rebuild is good housekeeping on a new engine and I'll do it anyway. It all just costs so much over here - $65 for the gasket set, let alone any needles!<br /><br />My engine does not have any mixture screws so no news on that front, and the compression is good. I believe that the smoke can only ever be caused could be caused by too much fuel/oli mixture getting through to the chamber, or too much oil in the fuel. Am I right in this or are there other things than can cause smoking?