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Posts: 81
Location: Van Buren, Indiana | This motor starts fine Idles like a purring kitten, but sometimes when you take off is only comes up to about half power. If you put it in nuetral and manually throttle it at the motor is revs up fine. We had it out two weeks ago first &second time we took off, half power at WOT, third time took off great came up on plane. 4th time back to half power. I'm thinking could it need decarbing with tuner spray? Could it be a coil problem? Any suggestions would be appreciated. It will probably go to the shop for a through check up this winter. I was just trying to remedy it for a few more trips yet this month!
Thanks Guys!  |
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Posts: 143
Location: Palatine, IL | I had a similar problem this year. Ended up being a bad plug. All of them looked fine, but I swapped them anyway before taking it in. Problem solved. |
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Posts: 81
Location: Van Buren, Indiana | Hey Weevil!
Thanks for the answer. I wondered about that too but it ran so good the first few times we took it out I did not think that would be it. We'll change 'em before the next outing!
Thanks again! |
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Posts: 143
Location: Palatine, IL | Let us know how it pans out. |
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Posts: 44
Location: Pewaukee, Wisconsin | You might have the S.L.O.W system kicking in. When the engine overheats or isn't getting oil it will limit RPMs to 2500, basically enough to get you back to the boat landing. Not saying that this is it but it is something to check. I have an 1989 Evinrude, had the same problem, it was a bad blocking diode that was setting off the S.L.O.W system. |
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Posts: 267
| Is there lower unit lube in it? |
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
As stated, I would start with something easy and is more preventative maintenance than anything... Change the plugs and test the motor out. QL78YC I believe will be the number on those from Champion. I also would suggest replacing the fuel filter on the engine as well. that should be on the right side of the engine as you are looking at it from the front.
I would also agree with doing a Decarbonization of the motor as well. Not sure if that year motor has a hook-up for it or not, so I'll try to describe what it looks like and where. Behind the carbs on the left hand side of the motor there might be a little red tab and a gray cover over the tip. Under that cover is what looks like a tire valve stem, which will accept a spray tube that attaches to a can of fogging oil or decarbonizer. Not all former OMC dealers have the nozzle anymore, but I would think you can find them on ebay or just call around...
After decarbonizing, take it out and really run it clean. Word of caution, though...you may want another set of new plugs as after decarbonizing, you may be blowing a bunch of gunk out of the powerhead, thus fouling a plug or two. I just got done doing that to my brother-in-law's johnson 50hp 3 cyl (same block as yours) and we fouled two sets before it ran clean.
If neither of these take care of the issue, then I would start looking at a carb rebuild.
In most cases like this, the issue is usually not electrical (outside of a fouling plug) as it is somewhat intermittent. With most other electrical components (coils most notably) go bad and stay bad from what I have experienced.
That engine is a great engine...I'm betting the top items here will solve your issue.
Steve |
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Posts: 81
Location: Van Buren, Indiana | Thanks guys for all the info. I checked the plugs and it does look like the bottom plug may not be firing well, it was not black like the other two, those will get changed real quick! Fuel filter was fine. Steve I did not have time to look for the air valve for the carbs. My '05 Johnson on my '04 180 Lowe Stinger, had the breather that came off with the rubber straps, this one unscrews. I will look at it this weekend. Your right this motor when it's running right is a good motor. It's on a '87 Arrowglass Runabout, its a little underpowered, but it will plane it fairly quick. This boat is growing on me, didn't think would like it at first, but it is a great multi species rig.
And it will store 9 plus footers down the side out of the way. If I still like it in a couple of years, will probably repower with a rebuilt '05 Johnson/Eveinrude 2-stroke from Outboard exchange. I just love the torque of the '05 Johnson 2-strokes!
Thanks Again!
(p.s. Steve, I may have to put a 6'' Hydro-Dynamics on this thing and sqeeze out all I can just for fun!) |
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Posts: 3508
Location: Elk River, Minnesota | HIya,
I don't think for the decarbonizing/fogging valve you would have to take off the air breather to do so...it should be right on the side with easy access. That year may not have that feature on it as I don't recall what year they brought that into the design. I sure like it, though... Had it on my 1999 50hp 2 cylinder and now on my 03 90hp.
Be interesting if you do the hydro dynamics on it. Fun to tweak everything out of it.
Steve |
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Posts: 81
Location: Van Buren, Indiana | Update finally got the boat back out yesterday, its not he plugs! The last time we had it out I felt like it was the Prop slipping but did not know for sure. When I first took off I put the hammer down, it took off fine, eased back on the throttle lost speed and seemed like lost power, run at that setting to 1st fishing spot. When we leave and try to go WOT same bogdown of motor. So I tell my buddy trim up the motor until you still have water but as high as you can go, engine runs up to FT. So he kept working with it until it locked up, we ran all the way across the lake on plane made one long slow turn stayed locked up, run straight a short distance make another sharper turn, BOOM, bow drops same, dogged running of the motor, found the problem, prop is slipping! The increased pressure in the turn was too much and it broke loose. It's a Comprop that looked like it has hit a few too many things, now confirmed. I just found a used aluminum 3 blade to replace it. Now will the ice stay away long enough to get it back out and find out!! |
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Posts: 81
Location: Van Buren, Indiana | Well not so fast on the prop slipping. I took it off after I posted thinking it was made like the others with a rubber hub and their not. The splines are molded into the hub, so now that is not the issue, it appears. I did forget to mention that when I changed the plugs the bottom plug did not have any residue like you normally see, it was just gray residue, like maybe it was not firing all the time. I checked that plug also when I was back home, same residue. It seems hard to believe that it could not be firing it does not run rough one bit. When it ran WOT throttle monday it had great power. Any thoughts anyone? When it runs right it is still a great motor, it might have to go i the shop for a good run through.
Looks like some of you guys might be riding sleds this weekend!
Edited by Ifishtolive 12/19/2012 9:13 AM
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Posts: 3508
Location: Elk River, Minnesota | Hiya,
something to check...
take the plugs out of the head but plug the bottom one into the spark plug wire. Set the other end of the plug in a place that can touch the block, then turn the motor over....see how much spark there is with multiple plugs. Then, check the other two cylinders and see if there is more or less spark using the same order of the plugs used to test the bottom. If there is more spark from all plugs, then change the coil from that bottom cylinder to a middle cylinder and re-test. If the low spark continues, you can narrow it down to that particular coil.
The next thing you can do is quickly do a compression check on the cylinders (if you have access to a tester...they aren't too expensive and nice to have when diagnosing a problem). Get the engine warm and then pull all plugs. Test each cylinder for compression. If that bottom cylinder does not hold, or is significantly lower in compression, it will show up here...
The other thing I would be wondering about is if you have a carb that just needs a good cleaning too. If a diaphram sticks closed or open here and there, it will show on the plug as well....
Couple of things to try out at home to help... Save you the shop money too.
Steve
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Posts: 56
Location: NJ | I had something similar happen on my evinrude last year. It would be fine for a bit then half power. Then it would "catch" and back to full throttle. Tried carb cleaning, changed fuel lines, new gas and new plugs. No changes. Turns out it was the power pack. Replaced it and problem solved. |
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Posts: 81
Location: Van Buren, Indiana | Weather was nice today so we checked compression, top 120, middle 120, bottom 115. Spark was even all three cylinders. I'm thinking powerpack is the problem. RubberUp, how much was the power pack? I am going to check with my dealer next week and see about getting one. Thanks Guys For all your help! I am ready for open water! |
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Posts: 46
| It's very likely either the powerpack or a coil. Coil is cheaper (about $30) so try that first. Then try the powerpack. Check eBay for parts to save $. |
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1990 70hp 2-stroke Evinrude Runs 1/2 power?