surge

[berdes]

Last season had some wires from the stator fry. Replaced the wires only. Everything seemed to work fine. That same season had a problem with the engine surging. That was prior to the burnt wire deal. Still have the surging problem. Maybe the two items were related ? 175 merc. sport jet.

[XstreamVking]

Charging system might be shorting? I had a 200 efi that had a worn out top crank bearing. The magnet would rub on the stator and short it out very briefly. Fried the stator wires and voltage regs.

[InjectorService]

There's definitely a reason those wires fried, I dont think just replacing the wires themselves was the fix. I'd start by checking stator personally.

I have seen the above as well.

[berdes]

Thanks, guy's. No longer have the tools or patience. Sent it off to the local dealer for repair. I'll post outcome in case it helps some one else.

[berdes]

Thanks, guy's. No longer have the tools or patience. Sent it off to the local dealer for repair. I'll post outcome in case it helps some one else.

The mechanic tells me the surging is due to a faulty switch box. I'll post the results if I ever get the boat back to test ride it.

[berdes]

Received word today that the switchbox was replaced and did not solve the problem. Was very happy to hear that.

[pcrussell50]

There's definitely a reason those wires fried, I dont think just replacing the wires themselves was the fix. I'd start by checking stator personally.

I have seen the above as well.

Some of the legends here recommend only soldered connections for the two yellow wires (the ones that most commonly seem to burn off their insulation). Just passing this on since nobody mentioned it yet. HTH.

===

Thanks, guy's. No longer have the tools or patience. Sent it off to the local dealer for repair. I'll post outcome in case it helps some one else.

Thank you. This is hugely helpful to people like me, who are not legends, to help us learn.

===

Does the Sport Jet use an airflow sensor? Or does it infer the mass airflow from throttle position, rpm, and manifold pressure?

-Peter

[Jim Speros]

Its always god practice to replace switch boxes in pairs. One of many reasons is a bad bias in one can kill a cylinder the other. I have seen flywheels and crank ends damaged too. The constant load - unload a jet boat sees is hard on the engine.

[berdes]

#7 - Neither. Motor is carbed, hence no sensors.
#8 - Mechanic tells me this motor has only one. I've never seen that, but hey, who am I to question a mechanic?

[pcrussell50]

If your motor is carbed you can get mid-high throttle surging from an over full float bowl, because a needle is not fully closing off the seat. Ask me how I know.

-Peter

[berdes]

If your motor is carbed you can get mid-high throttle surging from an over full float bowl, because a needle is not fully closing off the seat. Ask me how I know.

-Peter

Thanks, could this extra fuel be seen thru the throat while running ?

[pcrussell50]

Thanks, could this extra fuel be seen thru the throat while running ?

Yeppers. In my case one minute I’d be cruising at 3000 rpm, then next thing it would be 4000. It was hard to holding on one or the other. So not quite a rhythmic surging, but a surge of a sort.

Take the air box off the carbs and pump the bulb firm. While keeping it firm for 30s-1m see if fuel is coming back out one of the carb barrels or vent jets. (Or leaking anywhere else for that matter).

-Peter

[FMP]

A float at high level closing the needle during high rpm max draw out the main into the throttle bore causing too much fuel?

I'd say the opposite, needle sticking just enough to near empty the bowl and fuel starve the cyl. The leaning out will raise rpm but I'd think it would take more than a cyl or two to do 1000+ increase.

Read the plugs immediately after.

[pcrussell50]

A float at high level closing the needle during high rpm max draw out the main into the throttle bore causing too much fuel?

In my case, fuel would spray out the vent Jet and that forward facing tube that is ahead of the butterfly, when you squeezed the bulb firm. Cylinder number 4… the one where the fuel feed line enters the middle carb in the 2.4/200. Maybe it flooded that cylinder down so that when the motor should have been at 4000rpm, it was at 3000 instead?

-Peter

[berdes]

Got the boat back today. New stator, power pack, and trigger (switch box?). Engine won't idle smoothly sounds like a cement mixer. Put it back on trailer. Will check jet pump out for debris tomorrow but I think it sounds more like a rod. Checking out my supply of JD for now.
Question: I vaguely remember seeing in a user manual for the sport jet that the hose connection was only for flushing and not to be used to run the engine on. That the engine would overheat. "Mechanic" tells me they did not water test repairs but only ran it on the hose! If anyone can find that info and paste it here would be great. I've had no luck finding that user manual / guide again. Thanks

Found the information on running on the hose - say's run only at idle speed if on the hose! Checked jet, no debris. Ran compression test, all @ 90 +/-, low, but all OK for a pleasure rig. Checked for fuel overflow as suggested and that was OK also. Brought it back to the shop and finished bottle of JD waiting on response.