1988 Evinrude 120 V4 -Suddenly going into SLOW Mode at WOT. Video included

[JAK3CAL]

HERE is my Youtube video of the issue on my 1988 Evinrude 120 V4, with the VRO.
Shes been a great motor, no issues the last two seasons until suddenly last weekend I cannot get on plane and my engine wouldn't go over 3.5k RPM or so.
I posted to the Evinrude Facebook groups and got the usual "Carbs!" "Plugs!" responses.... until I filmed this video and everyone disappeared on me.

Hoping someone here has help. Ive seen similar posts here in the past (shoutout to @Sean Lloyd)

I have done: New fuel line, new fuel bulb, new fuel filter, new correctly gapped Champion spark plugs (also tried NGKs... problem persisted).
I have checked: Carb (Clean), Spark Plugs (Tested good), Spark Plug wires (Good resistance).

The engine appears to be going into SLOW mode (im assuming... ive never seen SLOW Mode nor is an alarm going off... who knows what electrical has been changed over the years). I followed the CDI Electronics debug process by disconnecting the tan wires at the back of the head. One wire (Tan with black stripe) briefly let the motor go over 5k before reverting back to SLOW mode. All three tan wires unplugged at the same time had no effect.

What else can I check? I am at a loss here... I secretly suspect the power pack is faulty but it could be coils as well (although would the spark plugs test and fire fine if the coils were shot? On my motorcycle that wasnt the case).

Hoping someone familiar with these old two stroke Evinrudes can help give me some advice. I am not optimistic a shop would want to or be able to work on such an old motor as this, at least any easier / cheaper then myself.

Cheers everyone!

 

[racerone]

Are you sure an 88 model has the S.L.O.W. feature ?------Start with a compression test and post your values.

 

[racerone]

The 1988 model does show that it has S.L.O.W. feature.------Likely the first year for that.

 

[JAK3CAL]

@crabby_bob

Are you sure an 88 model has the S.L.O.W. feature ?------Start with a compression test and post your values.

This model has SLOW. Compression is fine, check out my video its clearly going into SLOW. Hits 3.5k RPM and starts bouncing off the rev limiter or however the SLOW electronics works

The 1988 model does show that it has S.L.O.W. feature.------Likely the first year for that.

Yes, either first or second was my understanding. Engine model is E120TLCCA

 

[racerone]

trouble shoot electrical bits.-----How does it behave in gear ?

 

[saltchuckmatt]

HERE is my Youtube video of the issue on my 1988 Evinrude 120 V4, with the VRO.
Shes been a great motor, no issues the last two seasons until suddenly last weekend I cannot get on plane and my engine wouldn't go over 3.5k RPM or so.
I posted to the Evinrude Facebook groups and got the usual "Carbs!" "Plugs!" responses.... until I filmed this video and everyone disappeared on me.

Hoping someone here has help. Ive seen similar posts here in the past (shoutout to @Sean Lloyd)

I have done: New fuel line, new fuel bulb, new fuel filter, new correctly gapped Champion spark plugs (also tried NGKs... problem persisted).
I have checked: Carb (Clean), Spark Plugs (Tested good), Spark Plug wires (Good resistance).

The engine appears to be going into SLOW mode (im assuming... ive never seen SLOW Mode nor is an alarm going off... who knows what electrical has been changed over the years). I followed the CDI Electronics debug process by disconnecting the tan wires at the back of the head. One wire (Tan with black stripe) briefly let the motor go over 5k before reverting back to SLOW mode. All three tan wires unplugged at the same time had no effect.

What else can I check? I am at a loss here... I secretly suspect the power pack is faulty but it could be coils as well (although would the spark plugs test and fire fine if the coils were shot? On my motorcycle that wasnt the case).

Hoping someone familiar with these old two stroke Evinrudes can help give me some advice. I am not optimistic a shop would want to or be able to work on such an old motor as this, at least any easier / cheaper then myself.

Cheers everyone!

Neutral revving to that degree is not very good for your motor. A little rev to start it up is fine then you need to back off pretty quick and then let it warm up at a slightly higher idle. I too thought you would show us a video with it in gear doing what you said....that's the only way to test that without harming your engine. Outboards are set to "underload conditions". I hate to say it but I was grimacing while you were winding it up. What you explain could be a safe/slow mode condition or it could be that a cylinder or two are shutting down for numerous reasons. As an example, I once had a 90 HP that didn't seem to go fast enough and it turned out the main jets in one of the carbs came loose effecting one cylinder. I'm a little curious, when you take it out and run it (in gear) do you take it back and look at the condition of the plugs? I wish I know how the rev limiter works but I don't....could be faulty. By the way, any marine shop should or would be happy to work on your motor, it not to old.

 

[JAK3CAL]

trouble shoot electrical bits.-----How does it behave in gear ?

Just fine forward and reverse. Will cruise no issue, just will not go above 3500 RPM suddenly and is entering SLOW mode. Below that I can cruise no issues and idles perfect

 

[JAK3CAL]

I’m

Neutral revving to that degree is not very good for your motor. A little rev to start it up is fine then you need to back off pretty quick and then let it warm up at a slightly higher idle. I too thought you would show us a video with it in gear doing what you said....that's the only way to test that without harming your engine. Outboards are set to "underload conditions". I hate to say it but I was grimacing while you were winding it up. What you explain could be a safe/slow mode condition or it could be that a cylinder or two are shutting down for numerous reasons. As an example, I once had a 90 HP that didn't seem to go fast enough and it turned out the main jets in one of the carbs came loose effecting one cylinder. I'm a little curious, when you take it out and run it (in gear) do you take it back and look at the condition of the plugs? I wish I know how the rev limiter works but I don't....could be faulty. By the way, any marine shop should or would be happy to work on your motor, it not to old.

I did all my original testing under load out on the water, but on this day (the video) I was at the marina with my uncle (former marina owner and lifelong boat expert) and another mechanic who moseyed over to watch… they both directed the neutral testing so I hope it’s alright. I would never under normal conditions do so!

The boat cruises just fine below 3500 rpm, no idle issues, all good. It’s just hitting that rev limiter when I try to open her up. Plugs are new (both sets, champion and NGK) and are gapped and look fine upon return.
I’m assuming there’s a faulty sensor or power pack or thermo somewhere but although I’ve found lots of posts of this exact issue… no one seems to have a solution!


Good to know I could try and find a mechanic… I also do vintage motorcycles and it is next to impossible to find someone to service older model bikes. I’ve had to learn it all myself, which is fine as long as it’s within my realm

 

[saltchuckmatt]

I’m

I did all my original testing under load out on the water, but on this day (the video) I was at the marina with my uncle (former marina owner and lifelong boat expert) and another mechanic who moseyed over to watch… they both directed the neutral testing so I hope it’s alright. I would never under normal conditions do so!

The boat cruises just fine below 3500 rpm, no idle issues, all good. It’s just hitting that rev limiter when I try to open her up. Plugs are new (both sets, champion and NGK) and are gapped and look fine upon return.
I’m assuming there’s a faulty sensor or power pack or thermo somewhere but although I’ve found lots of posts of this exact issue… no one seems to have a solution!


Good to know I could try and find a mechanic… I also do vintage motorcycles and it is next to impossible to find someone to service older model bikes. I’ve had to learn it all myself, which is fine as long as it’s within my realm

Not sure 3500 would be considered a "slow mode" my outboard, while quite newer, takes me down to 1200 rpm's. Seems like 3500 if your running hot or low oil wouldn't be very "safe" did you read somewhere that that is the safe or slow RPM? Here is a screen shot of something I found with a comparable motor....I think your problems are elsewhere perhaps even under the flywheel. Be persistent and try to be systematic and you should find a solution.

 

[JAK3CAL]

Not sure 3500 would be considered a "slow mode" my outboard, while quite newer, takes me down to 1200 rpm's. Seems like 3500 if your running hot or low oil wouldn't be very "safe" did you read somewhere that that is the safe or slow RPM? Here is a screen shot of something I found with a comparable motor....I think your problems are elsewhere perhaps even under the flywheel. Be persistent and try to be systematic and you should find a solution.

WOT on this model is 5000-6000 RPM, and she regularly would hit those values until last weekend. 3500 RPM seemed in line with other posts ive seen, the tell tale engine bucking / shuddering (its very distinct). I am so positive it is SLOW mode although of course I can't know for sure.

 

[saltchuckmatt]

WOT on this model is 5000-6000 RPM, and she regularly would hit those values until last weekend. 3500 RPM seemed in line with other posts ive seen, the tell tale engine bucking / shuddering (its very distinct). I am so positive it is SLOW mode although of course I can't know for sure.

From everything I've read it 2500 for your motor. Did you read about the diod that can go out in your harness and cause it?

 

[JAK3CAL]

From everything I've read it 2500 for your motor. Did you read about the diod that can go out in your harness and cause it?

hmm... I do not have access to a manual; im just searching for this engine model on the forums and finding other posts regarding it.

I did see the Diode post, but I haven't checked that / am not sure what that component is yet

 

[tphoyt]

Not that this is going to help your problem but just out of curiosity what type of tac are you going by? Maybe it’s not all that accurate.

 

[JAK3CAL]

Not that this is going to help your problem but just out of curiosity what type of tac are you going by? Maybe it’s not all that accurate.

Tach on the boat, it’s accurate. She’s ran fine for two seasons I can feel her out good… this just popped up from one weekend to the next. She would
plane out at about 4k and easily get up into the 5ks and now it’s bouncing off the rev limiter / SLOW mode

 

[saltchuckmatt]

Tach on the boat, it’s accurate. She’s ran fine for two seasons I can feel her out good… this just popped up from one weekend to the next. She would
plane out at about 4k and easily get up into the 5ks and now it’s bouncing off the rev limiter / SLOW mode

Well, your convinced it slow mode and it might be....so look at the 4th reply in this thread/forum and then the other link is how to replace the diode. Doesn't look very fun.

Topic: ’93 70hp wiring harness diode? – Antique Outboard Motor Club,Inc

www.aomci.org

Diode Kit | Crowley Marine

SAFETYThese installation instructions contain information that can help prevent personal injury and damage to equipment.

www.crowleymarine.com