Bigger Cam vs Warm-up

[FreeBeeTony]

I recently rebuilt my 350Mag and installed a Comp Cams XM270HR.
Has a nice idle.......but seems to require more time to warm-up and idle.
Is this to be expected?

 

[Scott Danforth]

Check your plugs, you may be running rich. Either a choke adjuat or a jet adjust Should only need about 3-5 minutes of warm up.

Which t-stat are you running?

 

[wellcraft-classic210]

My 1980's 5.7l 260 hp boat needs a few minutes (2-3) to warm up before I can get into gear without stalling-- I usually try to run it at around 1100 rpm to get the oil flowing & speed thing up a bit.

The lack of a high idle on the Rochester Quad carb is part of that -- even with the choke optimized.

I suspect Merc omitted the high idle hardware that to protect the out-drive from going into gear at higher RPM's and any added forces associated with that.

 

[achris]

...

I suspect Merc omitted the high idle hardware that to protect the out-drive from going into gear at higher RPM's and any added forces associated with that.

This, and not just Merc, all marine engine should be without a fast idle cam on the carb. Even the MPIs don't have a high idle when cold.

Chris. ..

 

[FreeBeeTony]

Check your plugs, you may be running rich. Either a choke adjuat or a jet adjust Should only need about 3-5 minutes of warm up.

Which t-stat are you running?

Engine is not in the boat yet......so not under load.
If I am running Rich will I see a change in the plugs while not running under a load?

 

[Scott Danforth]

with a larger cam, you many times need to adjust idle mix and choke.

Under load she will warm up much faster.

 

[alldodge]

You need a Dual AFR meter, otherwise your checking plugs a whole lot and still may not have it right

 

[Scott Danforth]

I suspect Merc omitted the high idle hardware that to protect the out-drive from going into gear at higher RPM's and any added forces associated with that.

all marine motors are that way so you dont put the boat in gear and run over swimmers while at the dock.

 

[QBhoy]

My MPI has a cam. Makes for a lumpy and dirty idle. Just a trait of a cam, depending on what the cam is spec for. Usually the higher the lift or more aggressive it is, the worse the idle is. The idle control valve has a constant battle on my engine at tick over. Like I say. Very dirty, almost coughing and barking noise through the side exits.