96 C85 Hard Starting

[fuzzymaster]

Recently purchased a boat with C85 Yamaha, I replaced plugs, and fuel filter. I also decarbed. It seems to be a fuel problem as a touch of starting fluid will start it. Not sure where to go now, except maybe pulling carbs. It seems to run fine when I get it started.

[99yam40]

Does the choke close all of the way?
what is your starting procedure?

[fuzzymaster]

I will check the choke butterfly? when weather gets better. The choke works with the key tho.
Starting procedure is: pump bulb until firm, choke and try to start.

Will plug gap make any difference as long as it is in spec. I think I set them around .037"

[99yam40]

motors with chokes need a little air with the choke engaged also.
So lift the fast idle lever a little and hit the choke as the motor is turning over

[fuzzymaster]

Funny thing, I didn't know I had a fast idle lever, where exactly is it?

Doh! Never mind, I found it with some searching. Hopefully that will help alot. At least I will be giving it a fair chance to start now. When the rain stops I will give it a try. Thanks

[robert graham]

Experiment with slight changes in your starting procedure until you hit the "right" combination. On my C90 Yamaha I pump the prime until hard, leave my throttle lever closed/down position, then I crank on motor for about 3 or 4 seconds, let up on it for a couple of seconds and then resume cranking and she'll start right up every time....after initial warm-up/running the starting is instantaneous every time....

[fuzzymaster]

When I bought the boat it was still warm out, no problems, so I guess I'll have to find the cold starting combo. Thanks

By the way, great site here. Glad I found it.

[rodbolt17]

C90 motors used a prime start system which requires NO warm up lever advance.
NONE of the C85 had prime start.
ALL C85 motors require choking AND manual throttle advance to correctly start cold.

[fuzzymaster]

What is the difference between two starting systems? I assume the throttle advance adds more air to the mix?

[rodbolt17]

manualy advancing the throttle on a C85 will allow more fuel, more air AND advances ign timing.

the C90 has prime start.

based on engine and prime start thermal device temp it will automatically advance ign timing and add fuel as nessasary.

on a prime start engine advancing the throttle may make cold starts hard to impossible.

the CORRECT starting procedure MUST be used or it may be difficult to impossible to start cold.

starting fluid can and will damage pistons.

[fuzzymaster]

Tried to start it today, no go. Definitely flooded. I tried choke, throttle lever small amount, and never fired. I'll try no choke next time, or small amount after turning over.

[robert graham]

If it's flooded then turn off the choke...the last thing you need is a richer mixture...and open the throttle lever to provide more air....Sounds like your spark plugs may be wet/fuel fouled caused by this very rich start-up mixture...how do your plugs look?....Keep working on this and you'll get it down pat and she'll crank right up every time...good luck!

[fuzzymaster]

They're new plugs. I'm just doing something wrong to flood it. Thanks for the encouragement.

[robert graham]

If the fuel pump has a rip,hole or tear in the diaphragm it can cause raw fuel to get sucked directly into the crank area, bypassing the carbs/choke/induction system, and causing a very rich mixture. It's an easy check and cheap($50) and easy to replace. I guess you have no way of knowing if fuel pump has ever been replaced?...

[fuzzymaster]

I pulled the new NGK plugs out and put the old Champions back in. Motor started, no choke or throttle, I did use the throttle lever to get it warmed up. So I'll be getting a new set of Champions.
I did cross reference the two different plug and they were comparable.
NGK B8HS
Champion L78C