1992 Evinrude 2 stroke 70 hp 1/2 rpm and 1/2 power at WOT. Help me diagnose

[ijmckenzie]

Hey guys,

I've been reading these forums for a while but I can't seem to find any info on my current problem. Really what I need help with is diagnosing what part has gone bad. So here goes...

The problem: I was coming back from fishing the other day at WOT doing about 30 knots. All of a sudden the my rpms and speed dropped by roughly half. (I don't have a tach but speed went to 15 kn).

What I have done so far: I figured I might have a bad power pack so I cranked the boat up in the yard and started pulling the "spark plug connector heads." Sorry guys I actually don't have any formal training in engine repair so honestly I don't really know what to call certain things...So try to bare with me on that. Any way I pulled #1 spark plug connector(#1 being on the very top carb, #3 being the very bottom). Engine starts to stall and plug head clicks madly. So far so good. I pulled #2. Nothing happens. Engine keeps running. Here is the weird part. #2 only clicks when I hold it right up next to the plug head. Also the clicking seems weak compared with #1. Now I do know there is power flowing through #2. How you might ask. Well, I accidentally grabbed the pliers above the insulated part and shocked myself....so there is def power on #2. I pulled #3 and got the same result as #1.

From what I can tell this tells me that #2 carb is not firing. Why?

Could it be the ignition coil????

Well I switched #1 and #2 ignition coils and here is what happened....

I pulled the plug head on #1 carb (now with #2 coil) no clicking (same as I described above for #2) but engine still started to die. Pulled the plug head on #2 carb (w/ #1 coil) furious clicking but engine did not stall at all.

Seems to me (old) #2 coil is somewhat "bad" which could be related to the occasional stalling I have been seeing after running for a long time at idle. I think I am going to replace it anyway but it seems that the coil is not ultimately the problem I am facing now.

So....Now I am stumped. What can I test from here before I start having to throw parts at it till it works?

Also, I cleaned all the connections from power pack to spark plugs etc

Also I thought about the stator being bad? But honestly I have no idea if this is possible with the symptoms I have described...I did look at the stator and noticed a little bit of the "candle wax" dripping that can indicate a bad stator but I have no idea if it is actually bad or not.

I can post pics if that would be helpful to anyone.

Thanks in advance for all the help guys...This forum has already helped me through a few different issues and speaking for the people who don't really know what we are doing; we really appreciate all the help that those of you who do know what your doing give to us.

 

[pn]

Re: 1992 Evinrude 2 stroke 70 hp 1/2 rpm and 1/2 power at WOT. Help me diagnose

does sound like a coil issue, they seem to act up after heating up. An aside, for insurance i always like to know the compression readings, you might be able to borrow one from the local autoparts store. Taking a look at your sparkplugs (tip) after running may help w/ diagnosing.

 

[ijmckenzie]

Re: 1992 Evinrude 2 stroke 70 hp 1/2 rpm and 1/2 power at WOT. Help me diagnose

How do you figure its a coil issue? Seems like if it was a coil issue #1 carb would have stopped working and #2 would have started working when I switched them. And how do you figure the heating up part? It acts the same cold and hot. Am I just missing something here

Compression readings are good. Can't remember off the top of my head but I remember them being fine.

Also that reminds me I switched #1 and #2 spark plugs to no effect. (before I switched the coils). Also I checked the spark plug tips already. 1 and 3 were fine. #2 (the one that's acting up) seemed a little oily

 

[clanton]

Re: 1992 Evinrude 2 stroke 70 hp 1/2 rpm and 1/2 power at WOT. Help me diagnose

What are the compression numbers?

There should be 100s of post on the ignition and cooling system for this engine, do a search, if you can`t find anything, bump post back to top.

 

[ijmckenzie]

Re: 1992 Evinrude 2 stroke 70 hp 1/2 rpm and 1/2 power at WOT. Help me diagnose

I will make an effort to locate the compression numbers and post a reply. However, I can't seem to find anything posted with the same symptoms as my specific problem. I posted an updated question here:
http://forums.iboats.com/johnson-ev...get-one-cylinder-fire-603767.html#post4206410

Long story short is I have done everything suggested on various posts/forums and I still can't figure it out. As near as I can tell I have fuel, air and spark but no ignition.

As I detailed in the updated question I am beginning to suspect the (rarely at fault) reed valves.

Thanks for your reply though

 

[clanton]

Re: 1992 Evinrude 2 stroke 70 hp 1/2 rpm and 1/2 power at WOT. Help me diagnose

need a gap tester for spark test. Hearing a clicking does not mean much.
Check powerpack mounting plate bolts, that hold plate to block, plate must have good ground to block.
Check all pack wires behind this plate, wires rub plate and short to ground.
Check all pack ground wires.
Pulling the #2 plug wire will not cause engine to responsed like #1 and #3.
These engines have a history of failure of # 2 cylinder piston and rings. Compression test very important.

 

[ijmckenzie]

Re: 1992 Evinrude 2 stroke 70 hp 1/2 rpm and 1/2 power at WOT. Help me diagnose

Thanks Clanton,

I will check the wires on the power pack. I will also re-compression test and post back here.

Out of curiosity why will pulling the #2 plug not cause the engine to respond like #1 and #3?

Ian

 

[clanton]

Re: 1992 Evinrude 2 stroke 70 hp 1/2 rpm and 1/2 power at WOT. Help me diagnose

I don`t know, but there is an OMC service bulletin that addressed this.

 

[ijmckenzie]

Re: 1992 Evinrude 2 stroke 70 hp 1/2 rpm and 1/2 power at WOT. Help me diagnose

ok ya'll brace yourself for the bad news. Compression check came back 125,0,125. Seems something is wrong with the #2 piston or cylinder head or o rings or something. To be perfectly honest I'm not sure what the next step is so if anyone has delved this far into their motor feel free to give me some tips...otherwise I guess we can call this thread closed. I'll prob make a new one to see if I can get some help taking the pistons apart.