Sportjet 175 surge

[Regal1700jet]

hi all,
I have a 1998 Sportjet 175 that runs amazing 90% of the time. The other 10% it has an issue.
This weekend was a great example. Saturday I took the kids tubing and it ran perfect all day. Sunday I took my sister out for a cruise and the motor acted up.
Usually it happens after warming up, so here it goes...
On initial start I can tell if it’s going to act up. It has a hard time idling, but it does idle (just a low idle, like it’s barely running)

As I start to go the motor feels normal to about 3000rpm, but above 3000rpm it starts to fall on its face. If I keep increasing the throttle, eventually the motor picks up at around 5000rpm and runs like a champ.
Same this happens when slowing down.
Above 5000 rpm the boat runs great, as I back off the throttle it starts to sputter below 5000, but once it gets down to about 3000 it runs good again.
The worst part is, tomorrow it probably won’t do this again. It will run 100%.
Both switch boxes are new (1yr old) and when the boat is working it works great.
I was thinking it might be a timing issue but I’m not familiar with the Sportjet timing mechanism.
Any ideas?
Thanks in advance!

 

[Gym]

I'm thinking spark or carburation. When was the last spark plug change? Proper plugs & gap? The other thing you might try is a can of sea foam in the gas tank to clean out the carburators.

 

[Speedling]

I'm thinking spark or carburation. When was the last spark plug change? Proper plugs & gap? The other thing you might try is a can of sea foam in the gas tank to clean out the carburators.

Yeah, especially now that everything has ethenal, I usually jump to the carburetor.

 

[RedBarron55]

Check the fuel pump pressure.
A gauge in the line to the carbs.
My 90 did that and a rebuild on the pump fixed it.
Actually it would die and if i backed off on the throttle it would run.

 

[Diplomasta]

Replace the trigger. ? The wires wear out.