Carb overhaul

[brandonvarnell]

Hi, I have a 1974 Mercury 500 with two Tillotson ka-25a carbs. I have been having problems with it running at full power. All the symptoms pointed to a timing problem, but as it turns out my carbs need an overhaul. When the mechanic told me the price for him to do it, I decided try to fix it myself first.

I bought a rebuild kit and took the carbs apart and soaked them in Berryman overnight. Then I finished cleaning it out with spray carb cleaner and then compressed air. When I got it to the lake, it ran much better but not quite like it used to. After about an hour of pulling a tube, it began to revert back to its old self as of late and only run up to half throttle. Long story short, I need to have them either completely rebuilt or replaced, because a good cleaning just isn't getting it. The mechanic told me the the welch plugs definitely needed replacing, but they only come in a kit the is very costly. My question is, will it be cheaper to get rebuilt carbs and if so where can I get them......or should I have them completely rebuilt and where is the best place to get that done? Thanks a lot for your help.

Brandon

 

[Yepblaze]

Re: Carb overhaul

Rebuilt carbs are not sold (that I am aware of).

It is not uncommon to have to go through items such as carbs more than once, until the sludge, debris, or whatever passes through and stops plugging jets, or causing valving to stop acting correctly.

Perhaps this is a reason why many a shop won't even want to work on anything over 10+ (or whatever threshold they choose) years old.


As I have found, most times I can pull carbs, and clear problems with a can of aerosol carb cleaner, compressed air, and perhaps a gentle probe of the jets, without buying parts.

I do not, under most all circumstances remove welch plugs.

I have found parts for the older Merc. carbs to be very inexpensive when compared to their later model Japanese (and such) counterparts. An usually get them from my local dealer without issue.


If in fact, if your issue was caused from fuel system contaminates, coagulants, or just little booggers, it may take a few tries till fresh fuel is the only thing passing through the system.

This is a problem I see quite often where some one has an item "fixed" only to have an issue re-appear, then move onto something else because "it couldn't be that, I just had it done".

If it were me I'd pull the carbs, flush and blow them out. Clean or replace filters. And probably do the fuel pump w/check valves (order as a check valve kit it comes with diaphragm) and run it again.

But understand that if it was fuel contaminates that you fed it, and feed it them again the problems could happen again.

 

[brandonvarnell]

Re: Carb overhaul

I was very meticulous when I cleaned the carbs. I am certain that without replacing the welch plugs, I can't get them any cleaner. The holes are just too small to access. The kits cost $13 per carb, so I want to be sure that my problem will be solved before I take them back apart.