Help identifying my 150 Merc

[Radiant]

I bought a 150 merc a while back that looks to be a mixture of parts. The serial number on the block is B374589 which comes back as a 1988 150. The motor has a full 16 amp charging system, the port cylinder head part number is 15221-C1 and the starboard is 18419-C1. I also notice it has a horizontal front half, not vertical. Any ideas? I’ll post some pictures soon

[rock]

It's called a frankenmerc. There's millions of them running around.

Rock

[Radiant]

I guess so. Not a problem for me. It is a clean freshwater motor so I'm happy

[rock]

If it were mine I might research the head numbers to be sure there is not a huge difference in cc volumne.

Rock

[Radiant]

Yeah, the different part numbers caught my attention. Compression is even but that doesn't mean much

[Merc 2.5]

I got suckerd on a motor once , comp test came in at 120-125, couldn't get motor run at all under a load , come find out heads were cut and had 70lbsish with stock cc heads. Sounded great on a hose tho , it was a lesson learned ,,, I'm sure this isnt a issue with you but like rock sayin. I'd find out bout heads and even pull them and have a look ,cause u already no they been tinkered with!!

[Radiant]

I've ran it once. It bogged a bit if I got on the gas too hard. One thing I noticed was the trigger wire is hitting the stator wire when I open the throttle, so I can't get full timing out of the motor. The stator looks aftermarket and maybe it was mounted a 1/4 turn from where it needs to be. But I am not sure if it would even run like that. I noticed this after the test run. I am rebuilding the fuel pump and carbs now because the motor sat. Found some debris in there. And the inner liner of the fuel lines connecting the carbs separated from the outside, so I am assuming ethanol was ran through it.

[j_martin]

Electrically it don't matter which way the stator is turned. Mount it so the cables route properly. I'd replace all the lines in the fuel system. After you detail the carbs and fuel pump, and get the trigger to fully advance, it should go good.
Link-n-sync on a frankenmerc might be a bit of a trick. Run the symptoms by these guys. They are used to making fast motors out of scrap parts.

[Radiant]

Finally got the motor back together after I had ordered the wrong carb kits based on the serial number on the block. I have some WMH 33 carbs that are from a 90s 150. Anyone know what those adjustment screws on them should be set to? Motor has clean carbs, a rebuilt fuel pump, all new lines connecting the carbs, and I now have full advance of the timing after adjusting the stator.

The motor sounds exactly the same on the hose, Has a little bog at around 1500 rpm, it'll get past it, but you can clearly hear it. I need to replace the plugs still, haven't done that yet, it slipped my mind. I ran it on the hose and it idles smooth but it is just very slow to rev, it has no snap when you crack the throttle.

I checked for spark on all cylinders and it has spark going to the plugs. Also took another compression test now that the motor was warm. 100-110 psi on each

I'll do the plugs tomorrow and report back.

After that, I'll see if I set the timing, I haven't touched that since buying it. But the past owner said "it ran well" and he seemed like a trustworthy guy but lets see.

Anything I could be missing? Open to any suggestions

[Merc 2.5]

Did u look at plugs after runnin it? Sounds like mite b little rich down low

[Radiant]

New plugs didn't do much. It might sound slightly better but it is slight. The old plugs looked pretty new, no coloration on it, just a bit wet when I pulled them off right after running it. that is why I didn't think plugs would do much.

I'm running out of things, I ordered a tdc gauge so I can verify timing. Sounds like it is maybe running rich though. The carbs are not original to the motor, they are the WMH 33. Would anyone happen to know what the jetting should be? Could it be reeds? I didn't pull off the intake when cleaning the carbs, but they looked good from what I can see. It idles great though, no sneezing or anything. When you rev the motor you can see the carbs spraying fuel.

[TEXAS20225]

you can find all the answers to your questions on merc .net its duplicate to Mercurys Midas electronic parts catalog for get the serial number because wmh carbs are from the later model motas but you can find the carb numbers in this info and it will tell you what they came off of im thinking the heads numbers are from 2.4 motors but that yesteryear stuff and clouds abound for me

[TEXAS20225]

i looked them up for you they are from a 1994 175 probably entire reed plate too

[Radiant]

Interesting, do you think the jetting could be off? I remember it being .064 mains in all 6

[TEXAS20225]

all that information is on the web site? look up whats supposed to be in the in the 175 carbs and check it out also problems with outboards especially frank motas is common . you would be amazed at all the things ive discovered in a motor somebody else "fixed up" after rebuilding over 400 efi motors and not counting all the other things ive done like changing carb to efi and efi to carb 16 amp to 40 amp and vice versa the list is endless