1968 Merc 110 9.8hp - Sputters or stuck at mid rpm with passengers/load

M

MichaelAngelo1

Cadet
Joined
May 20, 2020
Messages
7
Picked up an old '68 Merc 110 9.8hp that runs OK as long as the 10' zodiac is empty. It does sputter a bit a mid rpm on full throttle but eventually revs up and planes the boat after a few seconds. The sputtering is just before the boat planes.

If I have another person aboard or there is load in the front, the engine will sputter at mid RPM and won't plane the boat.

Any ideas of what could be causing the motor to sputter under load and fail to get up on the RPMs?

I have a video of the sound here (click sound icon in the bottom-right if it doesn't play):

https://imgur.com/acFhnoo

Thanks for any suggestions!
 
jimmbo

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
14,109
No sound, at least on my iPhone, some nonsense about installing an App

Love the Red Decal from those years.
 
M

MichaelAngelo1

Cadet
Joined
May 20, 2020
Messages
7
Compression is 120 in both cylinders, cold. Quite amazed by that actually given how old the engine is.

Spark from both leads, but haven't got a inline spark tester on hand, will get one and get back to you. Here are the plugs I pulled (put in clean 2 trips ago):

Top cylinder:
yFszMIml.jpg
(had drop of gas between elements)
Bottom cylinder:
I1yEugwl.jpg


Note that these are new plugs I put in before the second trip, it already had original plugs in there and had the same issue with those. Will get a picture of the original plugs.
 
jimmbo

jimmbo

Supreme Mariner
Joined
May 24, 2004
Messages
14,109
Those Plugs aren't Perma Gap. Perma Gap was what Merc called the Surface Gap Plug. The gap on those plugs looks very small.
The current Recommend plug is a L4J gapped at 0.030"
 
You must log in or register to reply here.
Top