I'm having a problem with my 1990 Evinrude 70hp losing power while on plane. The problem has been intermittant and it doesn't show the same exact symptoms every time out. I have a really good mechanic who does my work for me, but when the problem first surfaced I immediately checked all the obvious stuff related to gas. New, gas, new tank, new hoses, etc. Same problem, runs good at idle AT FIRST then put it up on plane, run for a bit then it looses power and sometimes cuts off, but most of the time just bogs down until I am at 3/4 throttle and barely making way.
So after checking the gas I took it to my mechanic who suggested an ignition problem. First they checked compression which was on the money between all 3 cylinders....and had good spark on all 3 cylinders. They put it in the test tank and couldn't get it to fail. Being an intermittant problem my mechanic suggested that it could be the power pack. I agreed and got it replaced. They tested it again after replacing the pak - all looked good. I took the motor out.....same problem reared it's ugly head. Took it back, ran it in the test tank and I was there. It ran like a scolded dog for 20 minutes - no problem. Well, he said he would still dig deeper...took the flywheel off and the stator showed signs of melting. Went ahead and replaced that...while he was in he also replaced the recitifier. Felt certain this had to be the problem and that the motor was failing after heating up. Tested the boat in the tank after replacing the stator and all was good. I get the boat and take it out.....same old problem. At first it seemed like it might do OK.....ran OK at idle speed and too off like a shot from a gun when putting up on plane - for a second I thought all was good....then it bogged down again....AHHHH!!!
Going back to the basics I got a spare gas tank that my buddy had been running on his Evinrude all week and tried that just to rule out gas again. Same old problem........sounds like it's running on 2 cylinders or not getting gas. No problem starting and it normally runs at idle speed well and just gets worse when runnning it hard.
My mechanic says they could trouble shoot it fairly easily if they could just get it to fail in the tank. Frustrating that it runs fine in the tank, but awful when out on the water.
Hopefully he ran it in the tank again this evening and got it to fail. If not I suggested going ahead and replacing the 3 coils. He also said he was going to pull the carbs and take a look for any varnish, etc.
So does anybody have any bright ideas. This is the most frustrating thing I have gone through with an outboard and I have had a bunch. Maybe a reed valve?? I don't think that would be intermittant though.
Already asked, unfortunately I don't think he really has the time. He's a really good mechanic thought and has always treated me well in the past....that's why I hesitate to take it somewhere else...especially since he knows the history.:$
I'll bet a fuel restriction.Once the carb bowls ,or A carb bowl goes empty,you may be losing a cyl.How about a pinched fuel line,or a fuel line that has swollen inward,cutting fuel.I doubt that tank testing is giving the eng. the run for the money it needs to fai;l
Sounds like ignition to me. How old are your plug wires and other ignition components?
Also, have you tried running it with the cowling off? Sometimes exhaust leaking into the cowling can cause problems as can cowling fasteners being too close to plug wires (or so I've read in other places here for the latter).
I like mikesea's suggestions. At worst pull your carbs and rebuild them. The carb kit price is very reasonable and it is something you can do yourself.
Well, when I ran my buddies gas tank I used his hose. I have a water sepeartor and by passed all of that with his tank and a hose directly from the tank to the motor. By doing this I pretty much ruled out the fule line, gas, tank etc.
Most of the ignition components have been replaced at one time or another but I'm not exactly sure when. I think I am going to rebuild the carbs just as a precauson. We'll see.......but boy it is frustrating!
Petty - funny you asked about running it with the cowling off. I did do that on the water because other than load issues, that's the only thing I can see different from them running it in the tank and me running it on open water. Unfortunately running it on open water produced the same result. I run it for a few minutes at idle speed out of no-wake and it seems to run OK, then I put it up on plane and it takes off and bogs down little by little....getting worse by the minute. Normally by the time I am back to the no-wake zone I have it pegged at 3/4 throttle and I am barely making way.
Take a timing light and a buddy out next time. When it starts to bog have him check for loss of spark. I would still do the carbs if they haven't been done for a while. Put your fingers on the head and see if you can hold them there for a good five count. iwombat could be right but it is odd.
After I run it awhile I can hold my fingers on the cylinder head so I don't think it is overheating. The warning horn works fine so I know it is not going into SLOW.
Water pump seems to be fine - not sure about the thermostat.
I thought to replace the coils just to see what happens since it is an easy and cheap fix. I tend to think that it is failing when it gets hot, but I would think that it would get hot running in the tank also and then it would start breaking down.
As the engine starts to die,did you try squeezing the ball to force gas up to the engine.If not,try it.If it begins to run,its the fuel pump,assuming all the lines are air tight.What kind of fuel pump do you have. ?Are you using the old style that has 2 screws and a removable slotted screw so you can access the screen.Is the screen clean. Or is it a VRO seperate oil and gas.?
I had close to the same syptoms and it turned out to be the power pack on my 90hp Johnson. A breaking down power pack will display syptoms just like a fuel restriction problem. Have you ever replaced the pack?
Well, I got it back from the mechanic this evening. He called and said he pulled and rebuilt the carbs. Said that they did have some trash in them, but that wasn't necessarily causing the problem. He then asked what I wanted to do about the coils. I told him go ahead and replace all 3 with new ones. At this point another $100 and parts will be some piece of mind. Once again he had ran it in the tank and it ran flawlessly.
So I picked it up, drove down the road and dropper her in. I gave her a 30 minute work out and she never missed a tap. She saound like my old motor again. I'm not completely convinced until I make a few more trips, but I really do think it is fixed since every other time it failed quickly after launching.
So was it the coils or the carbs....well I guess I'll never know. Main thing is I got her running again in time for duck season. I tend to think it was the coils though........
Thanks for everyones input - I really appreciate it. I'm sure I'll be back before it is all over with. I own 4 outboards:$
Evinrude power loss troubleshooting
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