90HP Inline 6 Bogs Severely Under Power? Choppy Idle?

[79 Silverline]

Hello everybody, first post here at iBoats - awesome forum.<br /><br />Here's what I got - I'm running a 90HP Inline 6 of 78' or 79' vintage (Cowling decals and timing sticker look like/say 79', but some things don't appear to match up). Ever since I started her up this summer, she idles rough and will go out if left idling long enough. However, when you got on the power, she'd open up and fly.<br /><br />The problem happened when I was flying across the lake and hit a wake hard a couple times and the engine bogged severely. She will NOT go past about 1/4th of 1/3rd throttle. Sounds like needles and seats or jammed carbs right? Nope. I had just rebuilt all 3 carbs (floats, needles, seats, kits), and then field stripped, inspected and cleaned them two times that day to no avail. Fuel pump? I rebuilt it before the trip, and stripped and inspected it. It's fine too. Pumping the primer bulb shows that the carbs are full.<br /><br />Inspecting all 6 plugs, they look a little fouled from extra fuel/oil but that's no surprise. Didn't do any chops, obviously. Flashlight shows that I have all 6 pistons left and the cylinder walls are still present and accounted for. Before I left, all 6 had 150-155 PSI compression.<br /><br />I have a brand new CDI ignition switchbox and coil combo, and it obviously fires the engine up, it's just not keeping the fire lit at higher speed, and idle is choppy. Checked my connections already. Once I was home, a timing light shows missing ignition events that seem to coincide with the engine stuttering - it gets reaaaly bad when I try to mash the throttle. So it's spark.<br /><br />I'll try to round this off here as it's getting long winded - but could this problem be from a dying, but not yet fully dead trigger? I have no experience with outboards, and don't know how to test one of these things, or even remove it. Can a trigger start getting intermittent? I'd appreciate ANY information you guys could share, as I'm really not sure what the deal is or how to proceed. Thanks!

 

[79 Silverline]

Re: 90HP Inline 6 Bogs Severely Under Power? Choppy Idle?

^ bump. Any ideas?

 

[timmathis]

Re: 90HP Inline 6 Bogs Severely Under Power? Choppy Idle?

Triggers mostly just die!

 

[79 Silverline]

Re: 90HP Inline 6 Bogs Severely Under Power? Choppy Idle?

That's what I'm thinking - they usually either work or they die. However I can't think of any possible other reason why I'm dropping spark. The CDI switchbox/coil assembly is brand new, and appears to function correctly - it fires every single time I test it by jumping brown/white and tapping black to ground. Raking the black wire across a grounded piece of metal briefly results in an almost continous spark.<br /><br />Timing light shows that the coil is failing to fire sometimes, however I have reason to believe that it's the signal going to the switchbox that's bad. I'm going to stick an oscilloscope on the trigger wire (provided that I can locate which wire provides reference pulses to the switchbox). If I see missing pulses coming from the trigger, I'll know what it is. Anybody have any schematics of the trigger itself? Pinouts and wire colors? Thanks.

 

[Clams Canino]

Re: 90HP Inline 6 Bogs Severely Under Power? Choppy Idle?

1st check for overvoltage on the +12 line. I've seen overcharging do strange things on those things.<br /><br />-W

 

[79 Silverline]

Re: 90HP Inline 6 Bogs Severely Under Power? Choppy Idle?

Well, I checked for overvoltage, everything is fine. I did however notice that the spark really starts cutting out (and the engine starts bogging) RIGHT as the timing advance is coming in. Hmm. I tried yanking on the trigger wires while the motor was running, and it didn't do anything. I'm going to rip all my wiring out and lay in fresh wire to replace my cracking, aging wire anyways.<br /><br />As for my suspicion that the trigger and switchbox are acting up? Well it looks like I get to test my theory, because last night when it was dark, I jumpered the wrong white wire (12V switched) into the wrong white wire (trigger). Cooked my switchbox (AGAIN!? DAMN IT!) and my trigger too. Not going to throw tools... not going to get angry... Ok so I was pretty pissed off. On the bright side, I'll have replaced every questionable part. If this doesn't work, then I be my own uncle.

 

[Clams Canino]

Re: 90HP Inline 6 Bogs Severely Under Power? Choppy Idle?

Check Ebay for a very inexpensive replacement internal wire harness. <br /><br />-W