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96 Fast Strike Power Surge

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brjeep

New member
Hi All:

I am hoping for some advice to fix the following problem.

My 96 150 Fast Strike (J150GLEDB) has a power surge. At full throttle the engine will initially run at a hi-power mode and at about 5300 RPM; after running a few minutes the power will suddenly drop off to lower power mode and I get about 4700 RPM. Then the engine will switch back and forth between the high and lower power modes. The switching is sometimes every few seconds and sometimes less frequent. It isn't a graual powering up and down, rather it is a sudden switch. I can definitely feel the sudden acceleration and deceleration, so it isn't just in the tach.

I bought the engine just recently, so don't know its history. When first installed I coudn't get more than about 3500 RPM. My local mechanic checked it out and rebuilt the carburetors. Performance is much better now. I don't notice the switcing at low or mid RPM, but it is obvious at high RPM.

I'm hoping to diagnose and maintian the engine myself, so have not taken it back to the shop.

Any advice appreciated.
 
Sounds like you are dropping out spark on one cylinder, then re-gaining it, causing the fast,slow,fast issue.

You will have to do a thorough examination of the ignition system, starting with trying to figure out which cylinder is causing the problem.

If it were me, I would remove the top cowl, rig a timing light to #1, run the boat, watching the timing light. If #1 drops out, the light will quit flashing.
Proceed thru all six to try to pinpoint which cylinder is the culprit.

All that said, that is on the assumption that you are actually losing one cylinder.

Another possibility is a defective optical sensor in the ignition system. If you suspect that component, I would just shotgun it and see if it fixes the issue.
That is an easy replacement, and not too expensive, about 85 bucks.

Look up your engine on shop.evinrude.com, and on the throttle linkage page, it is ref #24.
 
If you haven't got a timing light you can also pull one plug wire at a time with an insulated pliers. You'll know which one is not firing right away.
 
Thanks for the responses.

ill give the timing light test a try. Hope to run the boat this weekend.Ill let you know how it goes.

Out of curiosity, once I discover the cylinder that intermittently stops firing, how do I fix it?
 
It is possible it is fuel related also connect it to a portable tank and see if the issue goes away. The best way to check for spark is just set the timing light on the deck and see if it is spark related when it hesitates. Around here you can just borrow a timing light at most any auto parts store. Nice to have one in your tool box if you plan on doing your own diagnostics.
 
As I said in my original post,

"All that said, that is on the assumption that you are actually losing one cylinder." I never said that was absolutely your problem.

All you are doing by using the timing light, is trying to determine IF you have an ignition problem. This is the easiest step, because you will have a visual indication, when that thing acts up, if it is ignition, you will see it. And it is a FREE test!!!

You said you had a local mechanic rebuild the carbs....so THEREFORE I specifically went to a POSSIBLE ignition problem FIRST (Kim).

Just find out if the ignition is acting up or not. Proceed from there.
 
Hi daselbee,

Apologies if I offended.

i understood and very much appreciated your reply.

I am new to outboard engines so was just curious about possible next steps.

i should be on the water Sunday, so wish me luck with the trouble shooting :).

thanks again!
 
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