View Full Version : Carb settings

07-07-2017, 12:27 AM
Boat: 2006 Outback (base model)
Engine: Indmar Assault 310 Carb
Prop: original. very slight curl to two fins, this is new

Problem: not getting to top speed. Was consistently getting 42mph and even got that this year until after I did some messing around and now only get 38/39 mph.

Situation/background:Had carb rebuilt when winterized last Fall, this Spring she ran well except the idle was at 450rpm's so wouldn't idle especially when cold, a little better when warm but often would stall when going from idle to in gear like when tightening up the rope for a skier. I thought messing with the throttle setting would help so I unclipped the link from the ball and played with threading until I thought the idle was better. Well I realize now that was the wrong thing to do, so adjusted the idle screw to get it set for the 750rpm's at idle. However, now when I run it at WOT it is 3-5 mph short of what it was. I took it out and it got to about 4,050 rpm's but as mentioned only 38mph. I tried adjusting the throttle connection to get it back to what it was and got a mile or two per hour more but not back to normal. The engine seems to run smooth in my opinion, perhaps a little rich as I smell gas in the exhaust but bought that was normal. It even idles nice, don't use the top speed much, just want it to run right and make sure nothing is wrong or going wrong.

Any thoughts would be very much appreciated.
Thanks in advance.

07-07-2017, 12:45 AM
I would get the prop fixed and see where that takes you.

07-07-2017, 02:52 PM
Thank you zabooda, the fin curl is very slight, is that enough to take 3-4 mph away?
Is 4050rpm about as high as this engine should go up to or is there more it should get?

Also, I was doing more digging in this forum on Carb questions and saw where the question was asked about carbon smudge on the side of the boat, I do have a noticeable amount of that on mine. So is that an indication it is running rich? If so, what is my best adjustment?


07-07-2017, 03:32 PM
I have an 03. It did the same thing to me always dying. I turned the screw on the carb 1/2 turn and that was 2 years ago and it doesn't stall now. Carbs suck lol. I have a very very slight curl in a fun and get 42 pretty easy. We don't ski behind it but my son Wakeboards. So have thought about getting more ballast and going with a 4 blade.

07-07-2017, 04:12 PM
Are you sure the speedo(s) is/are calibrated? Do you have the two adjustment knobs on the dash? I would verify speed with a GPS as those knobs are easy to bump and easily throw off the speedos.

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07-07-2017, 06:49 PM
Yes mine are verified with GPS. These are 3 blade props also not 4 blade. These boats are made to pull slalom and barefooters.

07-07-2017, 08:25 PM
Thanks GqJeff and Stazi.
I am not a big fan of the carb either, so sensitive like someone else know that sleeps next to me :)

I did check the speedo with a GPS app on my phone and it was dead on, not sure if that is reliable or not.

I am running the 3 blade original prop.

07-08-2017, 08:18 AM
Since it sounds like you messed with the linkage when trying to adjust idle the first thing to check is if you are getting WOT (wide open throttle). With the engine not running, pull the spark arrestor off the top of the carb, and push the throttle lever all the way down and leave it. Now use a flashlight and look down in the top of the carb to make sure the throttle plates are all the verticle. U will have to push open the choke plate at the top of the carb to see the primary throttle plates, which are a round disk inside each of the 4 bores at the bottom. If it's a vacuum secondary carb this won't work to check if the secondary is opening all the way. Send some pics of the carb

07-09-2017, 10:07 PM
Problem solved!!! Sheepishly I admit I didn't do what is often suggested as the first steps right away. Yesterday, I finally took the long drive to town and got new plugs and fuel filter. I found the filter quite clogged and one spark plug had two good cracks in it. Did these replacements, took her out and she runs as smooth and fast as ever! So relieved!!!

Thanks z28ke, I did take a look down the carb and with the lever all the way down the secondary plates did not open. So I am taking this to mean my carb is vacuum controlled.

Thanks to all of you for the thought and help. Sorry, I wasnt smart enough to take the correct first steps before jumping to more drastic conclusions. This is a great forum with terrific readers and contributors.

07-10-2017, 12:29 PM
Good deal, glad you got it figured out.