Time to Start Thnking...Carb Rebuild? (or not)

[gregmsr]

Ok, with all the brilliant minds here, can someone compile a list of problems, either visually or mechanically, that would indicate it's time for a carb rebuild?
I have read through previous threads and come to the conclusion that a rebuild should be avoided unless absolutely necessary.

You see, I have an 89 Force 125hp. 5500rpm @WOT, BUT, I still have a gut feeling a rebuild may (should) be done. (I've noticed some things that concern me)

Lets get these things running great for the coming season!!

 

[pnwboat]

Re: Time to Start Thnking...Carb Rebuild? (or not)

What "things" are you concerned about. I've learned in the past that the old saying "If it ain't broke, don't fix it" rings pretty true.

The first thing that I look for (I'm not an expert, others may have additional insight) are gas leaks from the carbs when the engine is down in the running position. If you tilt it way up, you may see some gas leak out but this is not uncommon. Make sure the primer bulb gets hard when you pump it. Also make sure no gas leaks from carbs when pumping bulb with the engine down in the running position.

If you are experiencing problems while under way, that's a little different. Need more details.

 

[gregmsr]

Re: Time to Start Thnking...Carb Rebuild? (or not)

My concerns:
Age of motor, 20 years

Runs good except at no-wake speed after warm up (wants to miss and quiver a little and sometimes cuts off, like a dead short for a split second). I decarb regular, change plugs regular, I re-built fuel pump diaphram, I run good-fresh gas @ 50:1, compression 125 +/- psi all cylinders, not sure on spark (checked with spark tester, what color should I have? Looked yellow, maybe)

It "sneezes" while starting

It dumps gas out the carbs when tilted all the way up (normal?)

Gas mileage seems to be getting worse

The primer bulb never seems to get real firm as I would expect (my first boat and not sure how firm it should get)

I do not notice any fuel leaks from carbs

From 1/4 to full throttle, runs like a sewing machine! 5500 rpm @ WOT, 35 mph (GPS, 19' Bayliner Cuddy)

Hesitates a little out the hole.

Anything ring a bell?

 

[sailfish252]

Re: Time to Start Thnking...Carb Rebuild? (or not)

Fuel leaking from the carbs when tilted up is normal. Before complete rebuilds on the carbs I would try to richen the idle circuit. This is done by backing out the adjustment screws on the carbs. Only go 1/8 turn at a time until you get a smooth idle with no sneezing. This should also take care of your hesitation comming out of the hole. Use a marine fuel system cleaner also it can't hurt.

 

[Frank Acampora]

Re: Time to Start Thnking...Carb Rebuild? (or not)

Listen to PNWBOAT!

Carbs stick right out there and just like women's nipples, men feel a compulsion to play with them.

If someone took a hammer to the carbs, then it is time to rebuild. If the floats are crumbling or fuel soaked, causing the engine to run rich and/or flood, then it is time to rebuild. If the inlet needles are no longer sealing, causing the engine to flood, then it is time to rebuild. Otherwise, leave them alone. If they are varnished, not likely since you use Seafoam, then a cleaning will do.

A soft fuel bulb has nothing to do with the carbs which are at the end of the line and everything to do with the fuel line up to the pump. So for that, you need to check for restrictions BEFORE the bulb.

 

[pnwboat]

Re: Time to Start Thnking...Carb Rebuild? (or not)

From what I've gathered from this Forum, the spark generated at an idle on these older Force ignition systems is lower than when at higher speeds.

I had a similar symptoms with my 1988 125 HP. Since it appears that you are only experiencing problems at idle speed, try this. With it idling, pull one spark plug wire off at a time and make a note of the idle. If you don't see a change in idle speed or the way the engine acts (jerking, missing), then that cylinder might not be getting a good spark. If only one cylinder is affected, then it may be a coil. If you have two wires that have no affect on idle, then it may be the CD unit that drives both of those coils.

If any spark plug wire(s) fails to make a change in idle speed when removed one at a time, you can test by switching the CD units ( kind of a pain) with each other, or move the coils around and see if the problem follows the CD units or the coils. What ever you do, do one at a time.

In my case, I had a bad CD unit. Engine idled rough, hard to keep going at idle, but above 1000 RPM ran good. When ever I pulled either number 1 or number 2 plug wire off one at a time, it made no difference. Motor still kind of idled rough. If I pulled 3 or 4 you could definitely tell a difference. RPMs dropped and engine idled even worse.

 

[mthieme]

Re: Time to Start Thnking...Carb Rebuild? (or not)

I have read through previous threads and come to the conclusion that a rebuild should be avoided unless absolutely necessary.

Not. It ain't a big deal. Some people are afraid of carbs though.
My 4.3 gets a rebuild about every four years or so. This is due mainly to the accelerator pump which only seems to last that long (I blame ethanol). I have a spare ready to swap out.
My older Mercs have all had rebuilds. They go further in between rebuilds. Go spares for them too.