1988 Evinrude 70hp help

[rfiglia]

I have a 1988 Evinrude 70hp. Its not running smooth until about 4-4500 rpm. At that speed it runs great. So in the driveway today at idle I pulled off the plug leads, the top 2 cylinders react when I pull the leads off, when I pull the bottom lead off the engine still runs the same, its getting spark on all 3. Seems like good strong spark even on the bottom cylinder. I switched 2 coils around and the same thing happens on the bottom cylinder. The plugs are new as are the wires. The compression is 120psi in all 3. Like I said below 4k rpms its souds like im running on 2 cylinders. Any suggestions? Thanks, Rich....

 

[mikesea]

Re: 1989 Evinrude 70hp help

Re: 1989 Evinrude 70hp help

seems like your bottom carb is dirty,mostly in the low speed jet area.you need to take it apart and clean it,while your at it do all 3,they should be disassembled,soaked in carb cleaner sold at auto stores,if you have compressed air,lblow through all passages,if not get a can of sprray carb cleaner and use it after you allow the soaking,just using spray cleaner is usually not good enough and will require double work,its not a hard job if you are mildly handy

 

[david_r]

Re: 1989 Evinrude 70hp help

Re: 1989 Evinrude 70hp help

sounds like you need to clean/rebuild your bottom carb.......wouldnt hurt to clean/rebuild all 3.....there are tips in the frequently asked questions on carb cleaning/rebuilding and adjustments.

if you have good spark but the motor doesnt change when you pull the plug you arent getting any gas to that cyl.......you have to have spark, fuel, air, and compression.

 

[tashasdaddy]

Re: 1989 Evinrude 70hp help

Re: 1989 Evinrude 70hp help

don't do just one carb, do them all. running the motor as it is will do great damage to the bottom cylinder.

 

[DJ]

Re: 1989 Evinrude 70hp help

Re: 1989 Evinrude 70hp help

don't do just one carb, do them all. running the motor as it is will do great damage to the bottom cylinder.

Yup, ask ME how I know that to be fact.

 

[rfiglia]

Re: 1988 Evinrude 70hp help

thanks for the replies, I just took a spray bottle of fuel and sprayed it into the lower carb while running at 1500 rpms, there was NO REACTION, when spraying into the middle and top carbs there WAS a reaction. Is it still the carb? There is good spark, when I pull the lead there is a strong spark from the lead to the plug when holding it away.... Thanks, Rich

 

[tashasdaddy]

Re: 1988 Evinrude 70hp help

compare your plugs, what do they look like.

 

[rfiglia]

Re: 1988 Evinrude 70hp help

They are brand new

 

[david_r]

Re: 1988 Evinrude 70hp help

do you have a timing light ?....if so hook it up to the bottom cyl and drive the boat and see if you are still getting spark above idle---all you have to do is watch for the flash..............im guessing when you are checking for spark any other time its idling or cranking with the key, correct?

 

[rfiglia]

Re: 1988 Evinrude 70hp help

the engine runs fine at high speed so I know im getting spark

 

[rfiglia]

Re: 1988 Evinrude 70hp help

compare your plugs, what do they look like.

Bottom plug is wet, seems like fuel is getting in there.

 

[tashasdaddy]

Re: 1988 Evinrude 70hp help

buy an adjustable spark tester. set it a 7/16 inch, and check spark.
http://www.amazon.com/Lisle-Ignitio...4?ie=UTF8&s=automotive&qid=1229280507&sr=1-14

 

[rfiglia]

Re: 1988 Evinrude 70hp help

going to get one now, will post results later...Thanks

 

[rfiglia]

Re: 1988 Evinrude 70hp help

ok, have spark at 1/2 inch gap while cranking engine on all 3 cylinders....

 

[DJ]

Re: 1988 Evinrude 70hp help

Compression? Should have no more than 5-10 psi. difference between all three. All over 100 psi.

 

[rfiglia]

Re: 1988 Evinrude 70hp help

as I stated in the first post compression is 120psi even in all 3 cylinders

 

[tashasdaddy]

Re: 1988 Evinrude 70hp help

well, you have 2 of the 3 things required. fuel is the next to test. which means carbs.

 

[rfiglia]

Re: 1988 Evinrude 70hp help

I understand what your saying but I sprayed fuel directly into lower carb with no reaction..

 

[david_r]

Re: 1988 Evinrude 70hp help

if you sprayed pre-mix into the carb while the prob was occuring and it didnt help.........i would say you are losing spark due to a bad connection, bad wire, or faulty ignition components....its very doubtful that you are losing compression at mid range so something is missing.

what is weird is it idles good and it runs at wot good.

 

[rfiglia]

Re: 1988 Evinrude 70hp help

yea this is crazy, engine starts up fine even the freezing cold here in NY. This up until now has been one of the best 70's I have ever owned. Like I said while the engine is running I pull the lead off the bottom plug, the spark is jumping from the lead to the plug, when I pull it further away from the plug to stop it from getting spark the engine does not react any different..