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wot problem and bogging

B

boatbo

New member
When I take off the engine sounds like its missing and it can not pull a skier up. Wide open throttle is about 3800 rpm should be 4400-4800.
I have put new fuel filter on and cleaned the one in the carb. I also put in fresh fuel and some dry gas. It runs strong at 3200 rpm with no missing.
Any help appreciated. Is this carb or ignition problem?
Boat is 2008 21 SSi Chaparral, 5.0 (220 HP) Two barrel carb. carb has sticker with following info. (SAEJ1223 Marine). Could not find any other tags. Is this a good # if I have to rebuild it? Thank Bobo.
 
For the small cost and I had this problem on my boat this spring I did a tune up, including wires, cap and in my case rotor and points, also check the timing, mine was off a few degrees, set it properly and it works very well. Bogging seems to be a common issue based on my own reading on forums but generally with older engines looking for a higher octane, many guys have put larger jets in to cure the issue.
 
The SJ number is a coast guard spec number. Not the part number.

Intially it sounds like your running out of fuel (lean).
There are several things to do but not sure of your experience level.
 
I know enough to be dangerous. I can do carb work, tune ups and have short blocked engines. I just don't do it on a regular basis. I identified the carb as a M2/mercarb. Which is no longer made. Sierra has a rebuild kt. Please let me know what you think might be the problem. Thanks.
 
Well loss of only top speed/wot throttle would suggest loss of fuel. If this is you only issue

So

1. First make sure firing order/spark plug wire order is correct.
2. check plugs for any signed of lean/rich.
3. get a second tank of some kind, supply motor with that fuel to see if it is a fuel restriction in your tank/lines.
4. Due to the year you are running an electric fuel pump so if possible you could confirm 6-8 psi at wot.
5. Check Vent lines to be sure gas tank is vented properly, Blow thru if clear then its clear.
6. if confident enough, have someone else drive the boat, wot, you have flame arrestor off, manually close choke some to fully closed when issue occurs. If it runs good then fuel/carb is the most likely source of the problem.
7. If none of the above lead you to the source (fuel related)

Then it could be ignition,

Dist cap, I believe your cap may be the type that has the flat top with the wires going out from both sides???????? There was an issue with these caps causing bad running conditions.

pick up sensor, inside distributor

Timing control module. (Last resort)

Possibly a bad knock sensor, this would retard timing limiting wot. Not sure it would cause a miss..........

Or a mechanical issue causing the knock sensor to activate. same result as bad knock sensor above

That is all I have during first cup of coffee...............
 
Thanks for the info. I did not think about the vent lines.
1. Distributor cap, all wires cone out of top not out of top sides, but I know what you ae talking about.
2. M2mercarb. They don't have a choke. They have an enhancement solenoid. (which is working).
I just feel like its a fuel issue. Bogging on take off reminds me of accelerator pump issue and high end could be dirt in carb.
I will check the plugs and look at the distributor first. (probably over the weekend)
Thanks again, any other thoughts, please advise. Hope the coffee was good.
 
If that is the "turn key" carb.............I am out........no experience with that one.............Thank god!!!!

I am fluent in all other crabs but not that one..........lots of past posts and not many are happy ones........

My opinion only.

I would, if you cannot easily resolve this, sh!t can the TKS carb and simply find a regular merc carb from an older 5.0 without all the "auxiliary" crap.
 
Had a persistent bogging with my TKS carb even with just 2 folks on board. Would sometimes stall dead. After long trials..

Per suggestion by Chris @ Dockside, I checked to see that the accelerator pump squirted AS SOON AS the throttle was advanced even the slightest, i.e. no delay. Mine didn't, traced problem to slop in the accelerator pump to throttle linkage link rod.
 
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