05 75hp merc missing wot

[Sirrobin53]

Well, having the same issue with this missing engine at wot. Idles well with just a little shaking which, what I have read, is common to the 3 cylinder engines. I have rebuilt the fuel pump, gone through the carburetors for the 3rd time, changed the coils, rectifier /regulator, plugs, trigger and the link/sync performed 5 times and verified 6. Timing is set at 19°BTDC at WOT. This was done in the shop, hot battery, charger on and plugs out cranking.
. The trigger was changed because the potting was cracked and it was sticking on the boss and not turning. The regulator / rectifier was changed because it was not charging and the wires were melted at the regulator and stator connections. It now charges @ 14.2v.
The problem is from 1/4 throttle to WOT. Seems to be missing when pegged at WOT. Let off to 3/4 throttle and missing quits. Ease throttle back in slowly and after 3 or 4 tries can get it to WOT.
Pumping the primer bulb makes no difference. All filters changed, new fuel lines.
IDK. I was hoping for a trouble free boating season. So much for that.
Any ideas?
I apologize for the long winded post.

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[racerone]

Post compression test results.-----Lots of work done but what about the water pump ?-----Checked for cylinder sleeve out of position ?----Run with a timing light to see if you can pinpoint the miss to a particular cylinder.

 

[Sirrobin53]

Water pump and lower unit oil change to compression 120-122 120. Because the trigger swelled and stuck it created it backfire. It blew the top seal out under the crankshaft. That was also replaced.

 

[Sirrobin53]

Tach is still erratic but its new and maybe not the proper one. Never goes much past 1000. Idles at about 750 though.

 

[Sirrobin53]

We are on Dale Hollow now with limited tools. Seems to idle well so we are Crappie Hunting for now.:joyous:

 

[Sirrobin53]

How much AC Ripple should there be coming out of the regulator? I have 60 volts

 

[The Force power]

Where do you have 60 volts? at the "regulator/Rectifier" or at the battery?

If its at the Battery; I'm pretty sure the regulator is no good
If its at the Rectifier/regulator; check the voltage at the battery if that is around 12 volt(or less), you probably have a bad wire/connection from the Rectifier/regulator to the battery

 

[Sirrobin53]

Removed the stator and found that it was melted around a couple of coils, with a burn hole in another one. I have one coming. Hope it will finally fix this problem. This is the only thing left to change in the ignition department.

 

[Sirrobin53]

So, can I expect that it has burned out the new regulator? I have 3 new CDM's on as well. Sheese. Where does it end? With a Yamaha ?:lol:

 

[The Force power]

Where does it end? With a Yamaha ?:lol:[/QUOTE]

Yamaha has made engines for Mercury since the late 70's (I like them)

To get back to the problem; where did you have 60 volts?

 

[Sirrobin53]

At the battery. I just replaced the regulator / rectifier because of burned connections and no charging. After replacement I have 14 volts to the battery @1800 RPM. All connections were soldered. On advice from many sources i also replaced the 3 CDM'S, and checked the battery with a hydrometer to be sure that it was ok. The burned connections on the regulator are symptoms of a bad battery that charges at full alternator output continuous. I still had missing issues at WOT and eratic performance and tachometer readings. All that is left is the stator......

 

[Sirrobin53]

Racerone, compression numbers.

 

[Sirrobin53]

This is a boat that was new me. PO may have had these issues and just got rid of it. When i got it the gearshift didn't function. In forward all the time. I replaced the impeller and lined up the shift linkage then upon removing the oil plug found only crystal clear water in LU. At some point the oil was changed and a gasket stuck on 1 screw and on the motor on the other. When the screws were replacd they were switched so 1 had 2 gaskets and the other had none.
And yes, I saw it run on the pipe. I was doing prevention maintenance so we could have a "relatively" trouble free boating season. So much for that. :lol:
Now just trying to get a season out of it B4 I run out of DOE.

 

[The Force power]

Ones you have the new Stator installed, you'll know if the Regulator is still good; lets keep our fingers crossed
this could solve the original problem

I would not run for too long, to prevent over-current to the electrical-system and have a battery connected

 

[Sirrobin53]

Going to Dale Hollow this afternoon for a couple of days. Going to chase the wild goose. Some say that the crappies are biting. Others have cleaned a couple of walleye. I will test the boat and report on the project as soon as I know something. I backed it in the water on the trailer yesterday at home for a test of the new stator. Tachometer was responding to the throttle and the engine was pushing against the truck pretty good. Promising results at least. I have my fingers and toes and eyes crossed. I hope that I find that I have won a battle. Not:deadhorse:

 

[Sirrobin53]

Put it in the water here at Dale Hollow yesterday. Same $&=$. Missing at wot. I admit defeat. No more money will be spent on it . Having a 70 Yamaha installed. I want to spend what little time I have left fighting fish, not a temperamental outboard .
Many thanks to all who have been gracious enough to respond with suggestions for repair.
Now I suppose I will have to be looking for help in the Yamaha forum:lol: