96 Merc 115 runs rough at higher range

[Maui Mark]

Hello everyone. Newbie here. My engine starts and idles pretty good. I'm aware of 2+2 as my father has an 02 Merc 125. My problem is the higher end. It misses out and the rpm's won't hold steady. Sometimes it runs great for a sec but mostly pretty bad. I did find a few exhaust plate bolts by no. 4 cyl that we're loose. Not finger loose but not as tight. I know they should be at 18 ft lbs. Saw leakage from one of them. Any insight? Thanks

 

[racerone]

Use a timing light to see if you have steady spark on all 4 cylinders as you increase the speed of the boat.

 

[Maui Mark]

Thanks. I do have new plugs, bulb, fuel lines, etc. I've just been looking for days and haven't really seen any concrete solutions. I even bought a new SS prop, 13"x 19p. Went riding with someone who knows quite a bit but scratched his head too. I'm trying to keep it simple before breaking out really big bucks! If anyone knows of a similar situation, with a cure, please let me know or direct me. Any response is appreciated. I would try to help anyone as well. I'll keep you posted if i discover anything. I know someone else is having the same issue. Thanks again!

 

[ondarvr]

Did you do what was suggested in post #2?

 

[Maui Mark]

No sir. This Saturday she gets compression check and timing light. I apologize that I didn't say that I just got this boat. Awesome price. Bought it as it ran. I'll get it dialed in. I found and replaced the accelerator filter that was very dirty. Checked the reeds. Adjusted the top 2 carb mixture screws. They were WAY out. I have all the confidence that it will be all good. I'll definitely keep you posted. I spent countless hours reading and searching posts. If this works I'll share for sure. Thanks

 

[Maui Mark]

Update. Cold compression was 120 across the board. Timing was right. Cleaned carbs, sync and link done. I have amazing idle for a 2+2. Going into gear very smooth. Hole shot and acceleration is basically the same. I'm still missing out. Rough at higher speed. I'm gonna put some NGK's and new wires. I've replaced the plugs but with Champion. New errors will be highly insulated.
I do have a question though. When we were putting it back together and i was attaching the voltage regulator on top of the air intake or carb cover, it arched when first touching the ground wire. I did not disconnect the battery. No key or switches on. Why would it do that? I'm not good with electricity. Just nuts and bolts. Thanks for your help.

 

[ondarvr]

Did you have the timing light connected while you were at high RPM's to tell if it was getting spark to each plug?

 

[Maui Mark]

Update. Realized that my accelerator pump was too low. I moved it close to the cam at WOT. It ran way better but still not 100%. Who ever worked on this before me did not know what they were doing. I'm no outboard mechanic but some things seem common knowledge. I'm getting spark too all plugs. I'm pulling the carbs again, adjusting flats, cleaning and replacing every single fuel and vacuum line that i can find. It's almost there. Thanks alot. The accelerator pump must be set properly. Not sure why it was moved.

 

[racerone]

Great story , keep posting on your efforts as we can all learn here.

 

[Tripp Halbert]

what are your symptoms at higher rpms? does your tach bounce back and forth by about 50-100 rpms? Does it feel like the motor is dragging more than it should?

 

[Maui Mark]

Trying to post updates. Keeps telling me unauthorized.

 

[Maui Mark]

Tripp, the motor is dragging over 3500 rpms. As racerone suggested, my timing isn't advancing properly at WOT. It starts right up, idles perfect and runs great on low end. Top end it drags. I feel it's electrical but not sure which part. We're gonna look at it more today. I appreciate the help. I'll keep posting the findings to help someone else out. And, my keys were in the wrong order, fixed that too. Of all the mechanical/fuel corrections, it pretty much runs the same.

 

[Maui Mark]

Jets, not keys.

 

[racerone]

Timing is fully advanced before you get full throttle opening !

 

[enginepower]

Sounds like a fuel pump with a torn diaphragm. It will still pump fuel but not enough volume for WOT. Get somebody to squeeze the primer bulb a couple of times when it happens and see if engine picks up.

 

[Maui Mark]

If I choke it, it stalls down, if I pump the bulb, nothing happens. Bulb stays full not hard. My timing on #1 isn't the same at WOT. I think it's 2? before TDC. At 5000 rpms should be 23?. I can't get to 5000. At my highest rpm it's 30?. Hopefully I make sense. Not good with electricity and ignition. I've been waiting for pump kits. There's no visible damage. Couldn't work on it today. I have a digital multimeter. Can I diagnose anything? I need step by step instructions. Thanks guys!

 

[Maui Mark]

Gonna pull the flywheel off and do an inspection. I hope I find something visibly wrong. I think that the stator has 4 settings. Don't want to get ahead of myself but you never know. This motor has had so many basic things incorrect you never know. I've learned so much in a few weeks. I've done 4 sea trials, at least I catch fish on stops when my buddy takes the cover off. My boat has redfish and speckled trout scales on it. The boat is good for something!

 

[Maui Mark]

Help, I checked the wires on the voltage regulator bolted on top of the carburetor. With the multimeter, ohms, I disconnected all 5 wires. 2 yellow, 2 red and 1 gray. With the black lead on the box, I touched all wires. I got a reading on all but 1 red wire. I reversed the leads with the red on the box. Touching all wires I got a reading on all but the same red wire. Should it read in both directions? From my extensive reading it shouldn't . Please advise, thanks.

 

[Maui Mark]

Carburetor cover

 

[enginepower]

Disconnect the voltage regulator and see if problem goes away. If it does, replace it. Here is a great online troubleshooting guide to help you determine ignition problems. http://www.cdielectronics.com/support/ . The only thing you will be able to do is the ohms test. You would have to make a DVA or buy one to test the voltages. I made mine for about $12 out of an old set of meter leads.

I was just looking at that guide and it has a part that describes your condition and says to disconnect rectifier as I suggested. If you have a rectifier AND a rectifier/regulator like I have, I would disconnect both. Does your tachometer do anything funny at high rpm's?