Merc 110 9.8 hp GASPING WHEN FULL THROTTLE

Tofuminator

Cadet
Joined
Feb 5, 2012
Messages
18
I have a merc 110 9.8 hp, thunderbolt edition. Starts on second pull, Idle's strong, low gear is fine but once I go full throttle it just spits and sputters, sounds a lot like it's gasping for air. I changed the spark plugs but it's still doing the same thing. Any suggestions?
 

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Most likely a fuel issue. Pull carb off, clean, and install a fresh carb kit. Depending on the year, the fuel pump is also part of the carb, and a kit will include the bits to update that, too.
 

Tofuminator

Cadet
Joined
Feb 5, 2012
Messages
18
Most likely a fuel issue. Pull carb off, clean, and install a fresh carb kit. Depending on the year, the fuel pump is also part of the carb, and a kit will include the bits to update that, too.

There is a seem above the prop on the lower unit I saw air coming out of, also I changed the oil and it's milky. Any suggestions? Please see pics and video. photo.PNG
 

Tofuminator

Cadet
Joined
Feb 5, 2012
Messages
18
Most likely a fuel issue. Pull carb off, clean, and install a fresh carb kit. Depending on the year, the fuel pump is also part of the carb, and a kit will include the bits to update that, too.

There is a seem above the prop on the lower unit I saw air coming out of, also I changed the oil and it's milky. Any suggestions? Please see pics and video.
 

Chinewalker

Fleet Admiral
Joined
Aug 19, 2001
Messages
8,902
Air coming out the seam is normal - it's exhaust. Most goes out the propeller but some will leak out that seam as there's no gasket there, nor is there supposed to be.

As for the milky oil, it's possible you simply need to replace the gaskets on the drain and vent screws. Worst case, you need to replace all the seals in the unit. Pressure testing the unit will tell you a lot.

Neither the exhaust leakage or the milky oil is the cause of your running issue...
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,047
Things for you to check.----Compression.-----Flywheel key.---If linkage on top of carburetor is plastic is it by chance broken ?--------Serial # is ?
 

Tofuminator

Cadet
Joined
Feb 5, 2012
Messages
18
Things for you to check.----Compression.-----Flywheel key.---If linkage on top of carburetor is plastic is it by chance broken ?--------Serial # is ?

Serial# 3924937 It's a 1974 Mercury 110 Thunderbolt edition. So Yesterday I took the Carburetor off and apart, it's clean as a whistle, no gunk no nothing. I'm just at a loss now what it could be?
 

BLKBEARD

Cadet
Joined
Sep 4, 2016
Messages
14
My 1984 9.8 was bogging down at WOT. I had replaced the plastic throttle linkage/arm which was cracked, that operates the throttle plate and didn't get it properly indexed. Once I properly adjusted it the problem cleared up immediately and the motor runs great.
 

Tofuminator

Cadet
Joined
Feb 5, 2012
Messages
18
Ok everyone, I found the issue and it was the fuel line fitting that plugs into the fuel tank, it had blockage and I bought a new fuel tank. I have a new PROBLEM! I took the carb apart to check for blockage before I found out it was the fitting and now when I prime the bulb there's no gas dripping/spraying through the needle into the carb. What the heck one thing after another. I took the carb apart again using a small plastic string and stuck it through the needle. Still the same problem, the bulb is hard but no gas dripping through the needle. The motor will start when i spray gas mixture directly into the carb, will also run just fine but will no start by pulling the rope until you spray gas directly into the carb. Brand new spark plugs. Can anyone help??????
 

60sboater

Petty Officer 1st Class
Joined
Jun 18, 2015
Messages
307
Try priming it more and see if fuel starts to drip out the front of the carb...then see if it starts. An old Mercury mechanic told me to try that on my '73 9.8hp. I did and could start it without shooting fuel into the carburetor.
 

racerone

Supreme Mariner
Joined
Dec 28, 2013
Messages
36,047
When you pull the choke knob is the choke fully closed and does it stay fully closed ?------Is float installed correctly ?
 
Top