View Full Version : 86 Fresh Engine - won't idle

06-28-2005, 09:18 PM
I just rebuilt the engine on my '86 with an Indmar 351W Ford. If I pump the throttle, the engine will run at or above 3000 rpm, but it won't run if I back off the throttle. It sounds great when it's running. The carb (Holley 600) has been rebuilt as well to no avail. I put a new fuel pump on the boat last year so I am hesitant to think that's it but I don't have a pressure gauge to know for sure.

I was able to keep it running around 1000 rpm long enough to make sure the timing is correct. New plugs, wires, distributor cap, points, condensor, rotor...

I still need to replace the fuel filter and clean the sending unit, and figure out how to better adjust the carb.

Does anyone have ideas as to what would cause this? And more importantly, how to fix it.


06-29-2005, 08:26 AM
I'm assuming that the carb is a Holley 600 CFM, or some form of a 4160 model. If that is the case, you might want to check the air idle adjustment screws on either side of the carb.

They are very small flat head screws, behind the front fuel bowls, and they may need adjusting. Snug them up (very gently), and then back them both out a full 1.5 turns. At that point, try to run the boat at idle, and make small adjustments to both sides to find the highest, smoothest sounding engine idle. You may have to readjust your idle speed at that point, and once you have, repeat the same procedure on your air idle adjustment screws. Let us know what you find out.

06-29-2005, 10:42 AM
Thanks, I'd been having trouble finding the starting position for the adjustment screws. I'll give that shot this weekend.

06-29-2005, 01:33 PM
What PeteS said. If that doesn't work, the I'd say your idle passages are plugged, and I would got fter that next w/a fine wire.


07-04-2005, 10:22 PM
The moral of this story is, if you're going to have a friend help put an engine together, watch what they're doing!

I took off the carb and the gasket, lo' and behold there was a washer on one of the studs under the gasket. Needless to say, I was sucking air from under the carb which kept it from running at low speeds.

Now, it runs great from idle to mid-range, then it bogs like it's starving for fuel. The fuel pump was still under warranty so I swapped it for a new one and have the same problem. The fuel filter is brand new also. I'm in the process of cleaning the tank and the pickup tube.

Does anyone know if the pickup tube is a one-way valve? I can blow compressed air thru it in one direction but not the other. It makes sense that it would be, but I'd like to hear it from someone who knows.

There are no pinched or dirty fuel lines and the vent from the gas tank to the back of the boat is clear. I adjusted the floats (on the trailer so I could level the carb). I'm not very good with carbs so any advice is helpful. The carb is very clean and freshly rebuilt. I'll be investing and installing a fuel pressure gauge this week so I can keep a closer eye on the fuel pump. Other than that, I'm at a loss.

Any input is greatly appreciated! Thanks

07-05-2005, 10:34 AM
I'll be investing and installing a fuel pressure gauge this week so I can keep a closer eye on the fuel pump.

That' what you need to do, right there. Once you get that gauge on there, post the results. That will tell us a lot.

You could also take it out and run it at the speed where it bogs for a solid minute, cut it off clean and pull plugs. Tell us what they look like.


07-05-2005, 11:09 PM
I seem to have a similar problem, but only when my engine is hot. I have a 1984 w/power slot. I have adjusted the carb for mixture, and even if I run lean, I still seem to not idle well when hot. If I run down the lake and then power down to idle, I run well for a few minutes then it will die if I don't rev. Tried similar things, plugs, points, electronic ignition, plug wires, new coil, rebuild carb.????? Didn't help with original ? much, but do have similar symptoms, except I run great before it gets hot.

07-06-2005, 12:13 AM
Mine runs a little worse when hot as well, but not majorly.

Are your fuel lines close to the engine and maybe getting too hot? I don't know the best way to check for vaporizing fuel, but it seems a fuel pressure guage would help identify if yours is a fuel delivery problem. Or perhaps you're getting too much fuel pressure and flooding the carb. It may be that it takes time to flood and that's why it seems like it's only happens when the engine is hot. I think the Holley's like 4-7psi while an Edlebrock or Carter wants less than 6.5psi. Check the specs for your specific carb for the preferred fuel pressure.

There are a lot of bright people on here so hopefully we can keep working on these things and post the solutions to help others!

Good luck!

07-18-2005, 06:32 PM
Willski, Did you figure out what is wrong with your boat, my 85 is doing the exact same thing!!!!

07-18-2005, 07:19 PM
Unfortunately I haven't been able to get back to the lake to try something new. My next steps will be the to add the fuel pressure gauge and I need to check dwell since I'm not confident it was properly set when the distributor was put back together.

It will be a couple weeks before I get to try these things but I will definitely post the results. Please do the same if you're successful with yours!