Looking for tower of power mechanic

[Hoosier Merc]

I am looking for a central Indiana mercury mechanic willing to troubleshoot my 80s Merc 90 inline 6. It runs and has given me two good seasons of use but needs tuned and I really don’t know how. I’ve replaced stator, trigger, and cdi boxes, plugs, cleaned carbs, replaced fuel pump internals. Local marina says too old and they won’t touch it.

 

[racerone]

What is the motor doing / not doing ??-----Have you replaced the water pump impeller ?------Throwing parts at it can be expensive.-------Start with posting results of a compression test.-----Then a spark check.-----Good spark jumps a gap of 3/8" with ease.---Check bleed inserts inside the bypass covers.-------And if it is hard to start you need to inspect starter and battery cables.----Have battery load tested , usually a free service.-----I promote testing and trouble shooting as it costs very little to find out what is wrong !!

 

[Chris1956]

Tuning on those Mercs consists of verifying idle pickup timing and max spark advance and making sure carbs are clean and synced to the spark. This is called Link and Synch.

Since you replaced the stator, trigger and switchboxes, did you perform the link and synch procedure?

 

[Hoosier Merc]

Thanks for responses. Main problem is idling rough and occasional dying at idle and or maneuvering at dock. Also really not making top end power like it did/ should. Last season, while out pulling tuber and with fairly loaded boat, rpms dropped from 5000 wot to about 4000-4200 wot and and hasn’t ever really been right since. Sorry for my delay getting back. Compression was even at 120+/-2 all cyls. I haven’t yet done spark check and bleed inserts. And now wondering if i dropped a coil?!? I haven’t done the link and synch since replacing the electricals. Looks like I’ve got some work cut out for me when the thaw comes. Pretty sure battery and cables are solid.

 

[Scott Danforth]

checking the plugs will tell you if you dropped a coil

 

[merc850]

Give us a serial Nr. to work with. So far it sounds like you are over propped.

 

[Hoosier Merc]

Ser # 5595490. 13” pitch 4 blade alum prop - drop in wot rpm from 5000 to ~4200 was like it fell off a cliff mid ride. No prop change involved. Was turning 5000wot with 23mph gps on my 19’ pontoon at beginning of season. I think it is/was propped right.
I’ve read that it can be tough to identify 1 of the six cycle not running on these...but really wondering if that’s not the ticket. I need to check spark and do the link and synch procedure as soon as the lake turns back to liquid. I have used the three step quicksilver fuel stuff as well as seafoam and use quicksilver oil premix with 90 octane no ethanol gas with an inline filter. Was really hoping to drop it off with a competent mechanic to make it perfect so I could go fish my first outing this spring.

 

[Hoosier Merc]

Cyl not cycle. Sorry.

 

[jimmbo]

Are any of the carbs leaking fuel out of the bleed orifice on the top of the fuel bowl while running?


You say you cleaned the carbs. A complete disassembly(including the shiny disks covering the idle and off idle ports) soaking in cleaner, then blowing out with air??

 

[racerone]

A competent mechanic may not touch it because you stated you wanted the old motor to be " perfect " again.------First make sure the carburetors are absolutely clean.-----Use a timing light on each cylinder to look for ignition issues.------It should not be hard to find the issue in my opinion !!-----Could be a bad sparkplug , plug wire or water on the gas.

 

[Hoosier Merc]

Gotcha. Thanks fellas. I get it. A lot of great ideas. I’ll reply when the world thaws and I figure it out or find somebody local who can help me do so. Perfect was the wrong word. 10-4 over and out.