1987 175 black max. Surging thoughts?

[Gsparks7724]

Was running very rough. Couldn't back up, it would die. Have to start with giving allot of throttle. When going forward I would give allot of throttle and then it would surge and run out no problem. Once I got below that spot it ran rough again.

pump bulb would do nothing, choke would kill engine.

replace fuels lines , bulb, cleaned carbs (looked clean), rebuilt fuel pump and changed enricher valve. Spark plug looked black like running rich.

took out on water and ran allot better but still has that little surge or spot where it gains more power and runs better. It will idol now and start easier. And I can back up without dieing

checked compression 5 are 120 and one is 112 or so. Oil system is removed (I mix oil in gas).

3 questions
1) could linkage adjustment fix This? Screws that adjust carbs and timing? If so which screws do I adjust to lean it out?

2) when someone removed the oil system they didn't plug vent line at the bottom of the block on fuel pump side. Should this be plugged? Fuel and oil comes out of this and makes a mess over the years.

3. What do you think is wrong? Could it be simple as bad gas?

 

[dingbat]

Two issues I see:
You didn’t clean and rebuild the carbs. Looking inside doesn’t cut it.

Your 112 reading is suspect.

When is the last time you decarbed the motor?

 

[Gsparks7724]

I did take the carb completely apart and cleaned it.

I have never decarbed it? What is that and how do I do that?

thank you for the advice.

 

[Dukedog]

I did take the carb completely apart and cleaned it.

use same gaskets?.. they need ta be replaced with new no mater how they look or come apart... all of 'em.

 

[Gsparks7724]

Decarb fixed it.

still know if that vent line should be plugged or not

 

[dingbat]

It’s been a while since I sold mine. What vent are you talking about?
if I remember correctly, the oil came down from the motor mounted tank to a metering device that then passed the oil on to the fuel pump for mixing. Don’t remember there being any other connections

btw: carry a spare reserve oil tank cap. Mine failed (on the water) as did a buddy of mine. Talk about a mess.....