Posted with a cutting out problem on my 1990 XP200 a couple of weeks ago (post name L77VJC4 vs QL77VJC4) and I was told to replace L77VJC4 w/QL77JC4's going to give it a try this weekend. What should I set the gap for? I premix 50:1 (vro unhooked)
Well since no-one wanted to suggest a plug gap I set the gap at .030. Started the motor and it fires on all 6 cylinders at idle, when you hit the throttle you can tell the power is not there it seems as though as soon as you get on it it will loose a cylinder. The carbs have all been cleaned when you shoot premix into the carb throats while high rpm running-no change. The maximum rpm it will turn at WOT is 5200 as compared to 5900-6000. Any ideas?? Does it sound like a power pack? Timer base?? I replaced the regulator/rectifier last summer and also the stator so I find it hard to belive one of them is bad.
The Q plugs gapped at 0.030" is correct. First step is doing a compression check on all six and then doing a 7/16" gap spark check on all six. If all that's good, next thing would be a factory manual. Then you can start with things like fuel and ignition components, but check the basics first and we'll go from there.<br />Good luck
If youre running it under a load with the airbox cover off, youre leaning it out severely. Do a compression check to make sure its still OK. Do not run it with the airbox cover off.
Dhadley only ran it long enough to squirt fuel into carb throats to see if somehow it could be a carb/fuel problem. I do have an omc factory manual for the motor. The motors idles perfect. I put an inline spark tester on each plug wire and started it and it would flash on each and every cylinder at idle, but as soon as I gave it throttle at approx 1500rpm you could almost feel a power drop like a cylinder quit firing. On my first outing this year at any rpm over 4000 the motor would just drop rpms for example 4000 to 3700 for 1/2 sec them back to 4000, now it no longer does this it just has no power. That is why I am thinking a power pack but I dont know if a bad power pack could be firing at idle and not at highter rpm's. I took all the plugs out and they are all have a nice "coffee" color to the ceramic. I will do a compression test and try to rig a spark tester and test this weekend and get back with the results. sorry about the long post
Long posts are usually good -- lots of detail.<br /><br />Yes, the motor can lose spark at any given rpm. Take your timing light and while someone else is driving just hook it to each plug wire. We're not so concerned about the actual timing but rather if the light flashes on each wire. It should be a nice steady light.<br /><br />And for goodness sake put that cover back on! Ive seen one lock up at less than 5000 that was running perfect. The guy was just curious to see if he could "improve" it with more air. The good news was that we put all new lightweight pistons in it when we rebuilt it.
I have a 89 GT-150 (basically same motor) that sound like it did the same thing.. The VRO pump packed it in and there's a sensor that senses this and will not let the engine run above a certain RPM... It idled and started great but when you put power to it, it would shut down one side of the cylinder banks (kills the spark)... Our quick fix was to unplug the VRO and mix our fuel at 50:1 and use a 12V automotive elec fuel pump... After we unpluged it, the engine ran great...<br /> So you might give this a try , but before you go buy a Elec fuel pump, mix some fuel at 50:1 in a tank, unplg the VRO and get someone to keep fuel pressure by squeezing the bulb.. Just to see if it is the VRO...
I have the vro unplugged on my motor and premix 50:1, but thanks for the suggestion. Dhadley I will do the timing light test and report back with the results!!
My 2000 200hp Johnson did the exact same thing, it would drop #5 cylinder after it came out of quick start, so when you started it, it would idle fine and when you started to go it would be OK, and then a cylinder would drop and come back periodically, I mean go from about 3500 to 4200 for 5 seconds and then drop back down. Turned out to be the timer base, not too bad of a fix, but the part was about $185.
I thought the power pack controlled the quick start/slow system. Did you try disconnecting the white w/black stripe wire from the head that controlls quick start to see if it would still drop out? My motor WAS dropping a cylinder for 1/2 sec at a time only above 4000 rpm now it seems as though she's gone for good at anything other than idle. Once I do the timing light test then maybe there is some way to check to find out if it's the timer base or power pack without having to buy both.
Well I originally posted this question in May and it is now almost December and I finally was able to run my boat!!! I wont get into the reasons why but they were actually legitimate. Well following Dhadley's advice did a compression check 105-105-103-103-105-105. When I started it on the driveway before going to the lake I noticed a little exhaust coming out between block and midsection, went to local dealer got water pump and powerhead base gasket. You ask whats water pump gotta do with this well I replace the darn thing once a year and I was 6 months behind! Removed the L77JC4 and replaced with QL77JC4. Filled with 30gals fresh fuel and a bottle of Seafoam just for good measure. Top RPM of the day 6440-87MPH on GPS. Never dropped a cylinder the whole day. On my original post (L77VJC4 vs QL77VJC4)OBJ stated, "the "Q"s are supressor plugs. Non-supression plugs can cause increased amounts of both radiated (radio) and conducted (electrical) noise. Such electro-magnetic interferance can raise hell on electronic ignition systems. This is why Qs were specified on your motor rather than the standard plugs. For the price of six Qs, I would change the plugs out then start troubleshooting from there." I have never run non "Q"s before and never wil not run them again!! Thanks to all for your advice and knowledge.<br />RED BOAT
