View Full Version : I'm back in the water but with questions

06-26-2006, 10:56 PM
Hello boys-

First if you all remember I had a timing issue and some others on my new to me 89' prostar 190 with the 351.

Here is what I did-

Plugs, accel wires, accel coil, full carb rebuild kit, cap, rotor, electronic ignition. I have been busy. Boat runs great.

I am back to the timing thing. I must have timed it 15 times today and found the sweet spot. Here is the deal, my RPM's are too high at idle with the scews turned all the way in. I also used to have the main idle screw turned in to increase the idle. Now I have the screw turned all the way out and it still idles too high.

Is there another ajustment on the carb or do I need to ajust the idle with the timing?

Also, the pumper thing that the secondaries are connected to, how does that work?

Thanks for the info so far. I am almost there.


Workin' 4 Toys
06-27-2006, 09:16 AM

BTW- Who rebuilt the carb?

06-27-2006, 11:18 AM
I did. It was pretty easy just time consuming.

Workin' 4 Toys
06-27-2006, 12:09 PM
I did. It was pretty easy just time consuming.
the pumper thing that the secondaries are connected to, how does that work?

I hate to jump to any conclusions........by your comment here, I'd guess this was your first rebuild?

06-27-2006, 12:31 PM
A lot of times in the rebuild kits, the secondary diaphrams "pumper thing" they provide will have linkage that is a little too short, causing the the secondardies to stay open a little. This may explain why you can't get the idle down. Next time you have it idling on the trailer, try and manually close the secondaries with your hand and see if it reduces idle speed. The only way to fix it is to buy another secondary diaphram and those are available at any auto parts store. The diaphram "pumper thing" is vaccuum actuated under engine load, which will open the secondaries up at a certain speed.

06-27-2006, 03:34 PM
IF this is a 4160 carb then you need to close the secondaries at idle. If you screw the mixture screws in all the way it should stall the motor. If it doesn't then you most likely either have the secondary throttle plate open or you have the main throttle plate way too far open. Did you carefully adjust the accelerator pump mechanism? It needs a small amount of clearance between the cam and the lever or it will 'piddle' fuel at idle due to the vibration of the motor. Any time you adjust your main idle speed screw you need to take a look at that clearance because adjusting the screw moves the cam one way or the other.

If this is not a 4160 carb then disregard most of the above.

Hope you get it going !!!


06-27-2006, 03:52 PM
Yes this was my first big carb rebuild. I have done a ton of Jet Skis and Motorcycles which I know are a ton different. I thought I would try on this.

I am going out right now to look into the accelerator pump and to see if the secondaries are open at idle.

I will post back. Thanks again for the info

06-29-2006, 02:42 PM
There is the idle adjustment near where the throttle cable is hooked to the carb -could this be the culprit particularly after adjusting all the other adjustments, maybe this is just not allowing the throttle to go all the way to its stop?

06-30-2006, 11:23 PM
Anyone know the stock jet size in my carb? 89' PS190 351. 4160 carb.

It has 63's in it now and I am at 6500 feet. Does that sound too big?

Also I have the powerslot 1:5:1 tranny does this reduce the gear or increase? Meaning, on my Supra I had a 1:1 tranny and the RPMS where real close to the speed. With the 1:5:1 would the RPMS be higher for a lower speed in general or the other way around.

One more question, I idle sometimes at 1k sometimes at 750 why would it fluctuate? I fixed the high idle problem I had eailer this week.

I think I have learned more about boats in 3 weeks than most do in a lifetime.

Thanks again for all the knowledge,