1990 Merc V135 Black Max Idle problems

[yland]

My 135 black max surges at idle from 600rpm up to 1200 rpms. The carbs were cleaned and are still very clean, all new 93 octane fuel in tank.
I had the same problem at 3500-4200 rpms until I took out the back draft jets.
I was wondering if I took out the idle air jets if this would stop my surging at idle or if it was something else.

 

[Barnacle_Bill]

Re: 1990 Merc V135 Black Max Idle problems

Possible pinholes in the fuel pump diaphram. If you rebuild it get the kit from Mercury as it contains newly designed check valves that will hold up when using fuel additives or E-10

 

[yland]

Re: 1990 Merc V135 Black Max Idle problems

Replaced the fuel pump and still surges between 600 and 1000 rpms.
Also now the alarm is going off.

 

[aussieflash]

Re: 1990 Merc V135 Black Max Idle problems

Also check tank air vent open and not restricted,no loose or cut fuel lines,dirty fuel filter,anti siphon valve (chuck in bin).Did you replace all needle n seats in Carbs,adjust float levels(very important),replace all carb gaskets,make sure carbs tightly re attached to reed block.Also check bleed line routing.Good Luck.

 

[Faztbullet]

Re: 1990 Merc V135 Black Max Idle problems

The surging could be a bad idle stabilizer raising and lowering timing, the horn is it a solid or intermittent tone?

 

[yland]

Re: 1990 Merc V135 Black Max Idle problems

The idle stabilizer sounds like a good bet.
The alarm is a solid tone that stays on. Sometimes it stays on after the boat is off. I tried
disconnecting the temp unit but i still get the alarm. I also ran the motor on a remote tank with a 50:1 mix and disconnected the oil injection line at the fuel pump. I got oil out of the line but i
was also getting gas out of the fuel pump. Isn't there a check valve that is supposed to stop gas
from being pumped into the oil line? Could that cause the alarm?

 

[aussieflash]

Re: 1990 Merc V135 Black Max Idle problems

Overheat alarm.Don't run engine and check compression,inspect plugs.
Have you checked off what I told you re your surge problems.

 

[Faztbullet]

Re: 1990 Merc V135 Black Max Idle problems

Disconnect the purple wire to oil module, if horn ceases the module is bad. The small elbow feeding the oil into fuel pump is a 2psi check ball style valve, if you have fuel coming from it with oil line disconnected its stuck or defective.

 

[yland]

Re: 1990 Merc V135 Black Max Idle problems

Okay well I haven't gotten a chance to check the idle stabilizer, but I did disconnect the purple wire and the Horn stopped. What does this purple wire do? Is that what feeds voltage to the unit from
the key switch. It looks like it runs from the module to the temp unit,
then through the voltage regulator and up to the key switch

 

[yland]

Re: 1990 Merc V135 Black Max Idle problems

Everything has been checked and re-check for the idle surging. Engine got new reeds, carb rebuild, all new gaskets all most all new fuel lines.
It seems like the idle stabilizer is advancing the timing at random if that makes sense.

 

[CharlieB]

Re: 1990 Merc V135 Black Max Idle problems

Remove the Idle stabilizer module and throw it into the trash. When they go bad they have a nasty habit of spitting a rod out the side of the motor at WOT.

Remove all spark plug, ground the wires, disconnect the throttle cable and tie the throttle /timing lever WOT, Set WOT timing to 23 degrees. You may have to readjust idle speed with idle timing adjustment once back on the water.

 

[Faztbullet]

Re: 1990 Merc V135 Black Max Idle problems

Just a note: The early model 135's(serial C100861-C221500) set at 21? as this will give the 19? at WOT. The engine serial numbers D082000 & up will set at 23?...

 

[yland]

Re: 1990 Merc V135 Black Max Idle problems

The Idle stabilizer can cause problems at WOT?? How does that happen?
I do have another problem, the serial number fell off the motor. From the carbs that were on it
I believe it was high C- low D range

Second what do I do with the Alarm and purple wire

 

[CharlieB]

Re: 1990 Merc V135 Black Max Idle problems

If any doubt to serial # set timing at 21, you may use 23 only if you use higher octane fuel, the difference in performance is not worth the additional cost.

Purple should be power supply to the alarm module.

It is possible the module has gone bad, Disconnect sensors, reconnect the purple, turn the key on, it should not alarm, if so, replace the module.

Once all wires are on and the key is ON, test the temp alarm. Ground the tan wire to a temp sensor, with the key ON the alarm should sound.

 

[j_martin]

Re: 1990 Merc V135 Black Max Idle problems

The Idle stabilizer can cause problems at WOT?? How does that happen?

The idle stabilizer messes with the timing, pulling the bias voltage on the switchboxes toward ground to advance the timing.

If it should short out and pull it to ground at WOT, timing will advance about 40 degrees. Your first indication would likely be a rod cap to the back of your head.

Either wear a helmet, or chit can the idle stabilizer.

 

[fisherman81654]

Re: 1990 Merc V135 Black Max Idle problems

The idle stabilizer messes with the timing, pulling the bias voltage on the switchboxes toward ground to advance the timing.

If it should short out and pull it to ground at WOT, timing will advance about 40 degrees. Your first indication would likely be a rod cap to the back of your head.

Either wear a helmet, or chit can the idle stabilizer.

lol real funny,but true.