1984 Mercury Black Max 150 hard start and wont idle.

[stevenmike]

I just picked up a 1984 Mercury Black Max 150 on a 1998 Skeeter SL185.

PO did not mix his oil correctly and was running heavy on oil. Checked compression on all cylinders 125psi. Drained tank of POs mystery mix and refilled with 30gal at 50:1

Took the boat out today, put in at Black Lake went out into Lake Maurepas by way of Blind River then back thru the river to the Diversion Canal.
When we put in she did not want to start. Took several minutes of cranking and adding throttle to finally get her to stay running. Motor ran OK, trim switch is acting up so trim keeps falling back all the way down. That said RPMs seemed to stay around 4800 with the throttle all the way forward.
When I stopped at Blind River Bar for about 10 mins and got back in the boat to head back to the launch the motor once again Took several minutes of cranking and throttle to get running. Had to bump throttle above idle in the no wake zone to keep the motor from stalling. Once back at Black Lake when attempting to idle onto the trailer she stalled again.

My question is where should I be looking to solve this? Ive read about the idle stabilizer causing issues and or failing with catastrophic results for the motor. What is involved in deleting that module? Just unplug wires from both sides and connect to eachother? What is the timing setup procedure once the module is bypassed?

Lastly whats a good PN# for a water pump kit? I put my serial in on Marineengine.com and got multiple PN# back for the water pump kit.

 

[jimmbo]

Welcome to iboats
At 4800 that engine is overloaded, WOT range for that motor is 5000-5500
Before you start throwing parts on it. Start with the Basics:
Can the Ignition System provide a Spark Strong enough to jump a 3/8" gap on every cylinder?
What did the plugs look like?
Are the Carbs clean, Floats set at the correct Height. extended hard starting is often a sign of dirty carbs.
Are you using the Fuel Enrichment System when trying to start it. That Motor doesn't have Chokes, but a system that sends some extra fuel into the Crankcase to provide a richer mixture.

Regarding the Power Trim. Unless you can hear the Trim Motor running, all the time, I suspect the system is bleeding down when under load from perhaps leaky seal or check valve. Have you checked the Fluid Level?
Is the Oil in the lower unit good?
Looking at the Pic, I would say that motor has seen a lot of sandbars.
The 150 has a lot of low end Torque, so I can't think of valid reason for that Thing bolted on to the Antiventilation Plate
Often there will be multiple Part#s, as not all kits are completely identical, some are more complete than others. FWIW, I would stick with Genuine Mercury/Quicksilver Parts

 

[Chris1956]

You might check to see if the choke is working, however, it is usually only needed when the motor is first started that day.

On my '93, a solenoid opens when the choke button is pushed. The solenoid lets fuel from the top carb drain into the throats of the two other carbs.

 

[stevenmike]

You might check to see if the choke is working, however, it is usually only needed when the motor is first started that day.

On my '93, a solenoid opens when the choke button is pushed. The solenoid lets fuel from the top carb drain into the throats of the two other carbs.

Choke sounds like its actuating but will verify by removing the aircleaner.

 

[stevenmike]

Welcome to iboats
At 4800 that engine is overloaded, WOT range for that motor is 5000-5500
Before you start throwing parts on it. Start with the Basics:
Can the Ignition System provide a Spark Strong enough to jump a 3/8" gap on every cylinder?
What did the plugs look like?
Are the Carbs clean, Floats set at the correct Height. extended hard starting is often a sign of dirty carbs.
Are you using the Fuel Enrichment System when trying to start it. That Motor doesn't have Chokes, but a system that sends some extra fuel into the Crankcase to provide a richer mixture.

Regarding the Power Trim. Unless you can hear the Trim Motor running, all the time, I suspect the system is bleeding down when under load from perhaps leaky seal or check valve. Have you checked the Fluid Level?
Is the Oil in the lower unit good?
Looking at the Pic, I would say that motor has seen a lot of sandbars.
The 150 has a lot of low end Torque, so I can't think of valid reason for that Thing bolted on to the Antiventilation Plate
Often there will be multiple Part#s, as not all kits are completely identical, some are more complete than others. FWIW, I would stick with Genuine Mercury/Quicksilver Parts

Plugs looked OK. Ordering new NGK plugs this week.
Unsure on carb condition. PO claims he cleaned them but he seems to be a moron. Having a friend that works on Mercs rebuild the carbs. If I push the key in I hear a click in the motor I'm assuming that's the fuel enrichment? Using that and not using that with throttle at idle will not crank. If I throttle up in neutral it will start.

Power trim. The switch feels "loose" when getting onto plane from stopped I adjusted the trim up before getting under way, got onto plane, heard the motor bog turned around and trim was all the way down. It seems like its powering down based on how quickly its trimming itself down.

Probably removing the whale tail on the fence dont want to change too much at once.

The lower unit has fresh quicksilver 80w90 in it. I just drained and filled Saturday.

 

[Dukedog]

think you might need ta find an OEM manual and go thru it.. yours has several answers for tha problems it has.. we can all guess but without actually being able ta "reach out and touch it" but with that many concerns it is all just that, guesses...
think this is tha manual ya need ta track down... jmo.

Service Manual 976583.. justa warning.. its gonna be a bit expensive in most folks mind but well worth it...

 

[Dukedog]

don't know your "startin'" routine but most carb mercs have their own quirks on what it wants... trim motor all tha way down.. raise fast idle up justa tad.. hold key pushed and crank till snorts and/or try's ta start.. release key and trim motor up ta level.. raise fast idle up a tad again and hit start WITHOUT depressing key.. this usually works till ya figure out what tha motor actually wants ta start........ jmo

this is justa a routine that usually works on a "HEALTHY" (all parts workin' as they should) motor,,,,

 

[stevenmike]

don't know your "startin'" routine but most carb mercs have their own quirks on what it wants... trim motor all tha way down.. raise fast idle up justa tad.. hold key pushed and crank till snorts and/or try's ta start.. release key and trim motor up ta level.. raise fast idle up a tad again and hit start WITHOUT depressing key.. this usually works till ya figure out what tha motor actually wants ta start........ jmo

this is justa a routine that usually works on a "HEALTHY" (all parts workin' as they should) motor,,,,

I think the idle module already has been deleted. Please see the attached pics of the motor. I can see where stuff used to be bolted.

 

[Dukedog]

yeah, its gone...