idle depends on the combo.  id get it on a hose @ home and close your gate valve a bit.  let it idle and get up to temp... 180 or so.  then set idle.  idle is all about setting the idle set screw, and idle mixture screws.

QUESTION How do I adjust the mixture screws on my carburetor?
ANSWER To set idle mixture screws: 1.Get the engine up to temp 2.Shut the engine off 3.Install a vacuum gauge to a full manifold vacuum port 4.Turn the screws all the way in until lightly seated 5.Next, back them out 1 full turn and restart the engine making sure the choke is completely off 6.While at idle, back them out 1/8 turn at a time, alternating between the 2 or 4, until highest vacuum is achieved. Be sure you keep all 2 or 4 screws even. You can also do this adjustment without a vacuum gauge, the adjustment are the same except you will adjust to highest engine RPM at idle.

once you have your idle set then when you go boating remember to set your valve to keep you around 180'ish at whatever rpm you cruise at. 

  id get it on a hose @ home and close your gate valve a bit.  let it idle and get up to temp... 180 or so.  then set idle. 

once you have your idle set then when you go boating remember to set your valve to keep you around 180'ish at whatever rpm you cruise at.

ka0tyk-   180* is kinda hot in a single pass system, 130* is plenty


ctm-   My heavy ass day cruiser runs at 1000+/-, for enough "push" around the docks and beaches, the lil boat runs 950+/-, both used mostly on the river. Pull some fwd out of it for the NWZ.

Daniel
Mash on it

Mine is at a 1000 or around 1100 and it is fine. Just right I think. Your better off doing it when your pump is fully sumerge under a load. You don't want any water running thru the motor under 2000 rpm's I think. 180 is a little warm for a couple more horsepower. Mine runs around 120 to 130. I took my valve off, less worries IMO.

hrmm ill try turning mine down a tad then.   

1000 in the water and about 1200 out. Boat runs about 140-160 in the summer.

I think my idle is set a little to high. I push a little to much wake at idle in the no wake zone. It's running
at around 1100 rpm. How low is to low?  Do I need to keep it high to keep water pumping through the engine?

If you have a flat tappet (non-roller lifter) camshaft, then I suggest you keep your idel speed at 900 rpm or above (900 rpm-1100 rpm). This will minimize the possibiliity of wiping your camshaft.  5 MPH Zone boat speeds may be regulated with your forward/reverse lever.

The higher your engine's operating temperature, the longer your engine will last (will wear less). There is nothing wrong wtih 160* F and in fact my jet boat operates at 160* F at speed; then when I come into a 5 MPH Zone, the water temp spikes to 190* F and then settles back down again.  Constantly running hard at 130* will accelerate engine wear, especially in the forward two cylinders. Conversely, running hard at 160*+ risks boiling over when you slow down, so pay close attention to your water temp behavior if you decide to slightly close your gate valve in search of a more "normal" operating temp.

LO

so does the valve in the boat matter??? when i got my boat last season i never touched it.. i watched the temp tho and it stays kind of cool..

  X2

once i got my carb jetted i can turn down my idle to about 800.  anything lower and when its cold i gotta bump the throttle a little to keep it running...

900-1000 rpms. 140-160 temp. All depends on your cam and intake setup for idle. If you can get away with idling at 500rpms then it's really up to you, how fast you do youwant to go at idle? Any more than a grand for me starts making wake and I like puttin' showin' my stuff when pulling up to the docks anyway...slow and low!    

I think the valve matters if youre running a t valve for the headers

It matters on all applications, not just headers.

You don't want to just let the valve be open, the casting plugs (aka freeze plugs) will fly up and smack you in the head.

A jet pump can generate in excess of 100PSI. Your shooting for under 20. 

The camshaft duration will determine RPM.