1983 Mercury 150 Vibration and Noise

[karnage]

Today I'm making a post about a performance issue on a project boat. I have been putting a boat together for a friend for about 14 months. 1995 Stratos 258 15' - 1983 Merc 150

I pulled the motor and controls off of another old boat i bought. The Mercury ran when I picked it up with minimal effort, been sitting for years. I shoved them into the Stratos and changed the stator, coils, diagnosed some ignition issues. I cleaned the carbs, new impellar and lower unit gear oil.

Today we finally took it out for its first overall test. Immediately I noticed a metallic grinding or intermittent deep noise. I thought maybe the bendix was stuck, or timing pointer or flywheel cover had something touching.

Motor runs and idles okay, hot day. Noise never went away. I didn't wanna run it too long, but I also wanted to diagnose it. It does it in neutral or in gear, doesn't really speed up too much or change. When i start to increase rpms under load, the entire boat shakes and engine will eventually stall.

By the time we got back to the ramp, the motor wasn't running too happy. Best scenario I made a mistake when replacing the stator under flywheel, or there is something up there needing help. Worst case, internal bearing?

I never heard this noise on the muffs, and this is the first time putting a load on this engine. Thoughts? Video below.

 

[racerone]

This motor sounds awful.-----Post the results of a compression test.

 

[karnage]

This motor sounds awful.-----Post the results of a compression test.

Forgot to mention I had done a compression test before removing the motor for transplant and it read pretty consistent across the board, around 120psi.

I suppose it might be time to test again if my performance has truly worsened. I'm going to order my own compression gauge now.

I have videos of it running on muffs under no load sounding, well, okay. Hitting on all 6 and taking throttle. (I don't think I could hear this issue over the open exhaust).

 

[jimmbo]

All the wires to and from the Switchboxs didn't get scrambled when you were making other changes to the Ignition system?
Do another Compression Test.
I think 84 was the first yr where the Engine mixed the Oil into the Gas, so I hope you were running Premix

 

[karnage]

All the wires to and from the Switchboxs didn't get scrambled when you were making other changes to the Ignition system?
Do another Compression Test.
I think 84 was the first yr where the Engine mixed the Oil into the Gas, so I hope you were running Premix

It is possible, but I do believe my ignition and firing order was well. The old trigger wire, and wire to the coils from the switchboxes is questionable. But, with the crazy vibration and noise I'm guessing something else. I've never felt a misfire make something shake so violently.

I am indeed running premix. Compression test will be done soon. I may post a clip of this engine running previously on muffs.

 

[jimmbo]

Keep in mind, with a 2 stroke, if there a very early spark, while the Transfer Ports are open, the Flame front can travel back into the Crankcase, as well as trying to push against the Piston coming up.
When on the Muffs, the noise of the Exhaust, as well as the Lack of any Back Pressure, may have hidden what you witnessed on the Water

 

[racerone]

They all sound good on a hose.----Even running on 4 of 6 cylinders.

 

[Chris1956]

Plug wires on the correct spark plugs? Firing order is usually 1-2-3-4-5-6 on those 60* V6 engines.

 

[Dukedog]

its not runnin' on all six for a start................. even at idle.