TOPIC: Fuel starvation

Ok question. is there a fuel filter located anywhere on my 1968 merc 125?
I can only get about 3/4 throttle and the it just starves.i have not held it open for more then a couple seconds for fear of damage. any ideas? it runs great up until 3/4 throttle.

I ask about filter because it seems like it should not completely go away if I have one bad pump so I was thinking clog?

on the top of each carb is one each. in the 6 gallon tanks there is a screen. you may have something else aftermarket , check.

my tank does not have one and it seems if one carb is plugged it would at least misfire. this is smoth as can be until 3/4 throttle. then it just starts to faulter.

Damn! I had a 74 Switzer XS 1500, 76 P/W..(torched the orig block) I had the damn same problem! Runs like a bear until it lays over hitting WOT? Well my race Merc Mech had just got a service bulletin to yank the small screens just before gas line going into in the float bowl.

SB said "take them out". Yep sure as chit, one carb was not getting gas WOT..clogged. Look into this first, before a "WTF "tail chase". Wish the best luck finding the prob..

Thanks guys I appreciate the help.

Check to see what ID the fuel tank pick up tube is. 1/4" is minimum for an inline-6.
Check the tank cap's vent holes - or simply remove the cap and try wide open throttle.
Check to see if you have after-market bayonet fittings. The female ones with a flat disk rather than a stainless steel ball will not feed a 1250 at WOT.
The plastic male internals will also restrict an inline-6's ability to perform at WOT.
Use of OMC fuel dis-connect fittings will not feed some of the larger jetted fuel demanding inline-6s.
If ethanol blended fuel has been used in the past in the tank or Merc, check the fuel hoses for collapsed inner linings that can block off fuel flow.
doc

I don't have a clue what fuel was used before I got it from tim c. I am going to redo all the lines this winter.I was hoping there was a main filter inline that I could replace. I am going away for a couple days but I will give it a looksee

You can certainly add an inline filter either between the fuel pumps and the carburetors [would take (2) on a 1250 due to the 'loop delivery'], so I would encourage installing a water separator-fuel filter in the bilge between the fuel tank(s) and the Merc.
Track down one with a drain pet-cock system on the bottom of the filter.
Placement of the prime bulb can be either between the tank & the filter (best IMHO) or after the filter if the design of your bilge and splash-well dictate placement aft of the filter for access.
doc

I don't think I am going to add one for fear of more restriction. I am going away for a few days and then I am going to bring it home so I can get a better look at the carbs. do you have a pic of the filter that is on the carb that the other guy was talking about doc.

If you are referring to me on the lines into the carbs, heck that was a long time ago so I simple can't remember. I do remember it was a easy fix, as think it only involved unscrewing the gas line, and it was a small screen in the fitting to the carb. I simple can't remember as that was 40 years ago. I just took a fast look my IL6, but as a "Frankenmerc", Doc might know more as he might have come across similar.

Here ya go gents!
doc

The carb in the illustration looks similar to those on my 1964 650. One caution, when you tighten bolt #18 that holds the cover #16 on, go easy and careful. Seems the area that the bolt threads into in part # 9 has a habit of breaking if the bolt is overtightened. Photo is the filter area on one of my carbs when I took them apart. Hard to believe but it was still running OK, but I cleaned them anyhow. Looked like beach sand. It had accumulated in the "before" side of the filter screen.

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Yeah Doc, small screens going into the carbs. It was on my XS, and pulled my hair out trying everything to no avail. Called Ralph back there (Ill), and he told me "take'em out" ! Worked.

they don't break because of over tightening but because the cover is sitting on the edge of the top and cocked. so it is pulling sideways.