25hp Merc idling issue

[NCjakeh]

I have a 1993 mercury 25 with controls. Ran good for a while then one day it just wouldn't idle or even run at a low speed. It's really hard to crank up. Takes about 30 minutes and you have to slam the throttle all the way up as soon as it cranks so it doesn't bog back out. It'll run like a champ wide open but anything less than that it will have none of it. Had the carb professionally cleaned in a sonic cleaner still the same issue. It's got good gas in it and I run stabil. Without wasting a bunch of time and money what do I need to look at first?

Also it won't crank unless you choke it. Doesn't matter how cold or hot the engine is

 

[flyingscott]

Compression and spark check need to be done. Was the carb rebuilt with all new gaskets?

 

[ondarvr]

So that everyone is using the same terms, cranking is you turning the key and having the starter spin the motor, starting is the next step. So I assume it's cranking fine, just hard to start.


​As mentioned, check for spark and compression.

It's not hard to clean the carb and it may need that done again, there are many small passages that need to be very clean, it's not uncommon for someone to not get everything completely clean on the first attempt.

Stabil doesn't help in this situation, so don't add it to the gas.

Does the squeeze bulb pump up and get hard?

 

[racerone]

Do some real tests.----------Does spark jump a gap of 3/8" on both leads, yes or no ?----------Does spark appear to be bright and snappy on both leads , yes or no ?

 

[racerone]

After this much cranking you may have damaged the electric starter.-------If there is a manual starter try using that and see if it starts easily.------Slow cranking may mean weak / no spark on these motors.