Boat Shows and Photos - 1991 150hp looper wont idle down

Hello, new to tht but have been gettin info and reading posts for years, much appreciated! I recently purchased a 1991 pursuit 2550 walkaround. Engines checked out and everything worked perfectly during the sea trial of course. I have twin looper 150's and the port motor takes 4 to 5 min to idle down after strarting and even after its warmed up. I suspect it has something to do with the quickstart feature on the engine. I have swaped the power packs and the motor wouldn't run with the power pack off of the other motor so it seems like the ignition system has been changed. I am trying to diagnose the problem before buying any new parts. Any help would be greatly appreciated!!

I have some experience with a 1991 120 looper that behaved sorta the same way- high idle, sometimes unsteady and might not return to idle when throttled down at the end of a run on-plane.

I found several issues:
- crankcase pulse fitting for the VRO pump was the original black one- I replaced with the improved blue fitting.
- several broken fuel line clamps allowed the fuel pump to suck some air- replaced.
- some nuts and bolts holding the carbs down were loose- re-torqued.

Solved my running problems. Mine still has the original powerpack.

i dont think its a fuel issue because once it idles down it runs perfect till i shut it off and start it again. then it idles high again for several min and same deal.

There is both a time-after-starting and engine temperature control for idle speed on the loopers. I replaced the thermostats in mine. Have you ever changed your t'stats or monitored the engine temperatures during warm-up? Maybe your troublesome motor is running cold?

Quickstart works by advancing ignition timing at start-up and for cold running. Have you put a timing light on the motor to see if that's what's going on? When was the ignition timing (link and sync) last checked?

If the motors are the same brand/model/year, it is odd that one will not run with the power pack from the other.

This thread should be moved to a different forum- nothing to do with boat shows and photos.

if its an after market power pack sometimes the wire color is wrong but sounds like the temp sensor in the head is failing or your themostats are stuck open .the temp sensor failing could just be bad ground or dirty

if its an after market power pack sometimes the wire color is wrong but sounds like the temp sensor in the head is failing or your themostats are stuck open .the temp sensor failing could just be bad ground or dirty

Good point about the temp sensors. When my 120 looper was delivered new, both sensors were faulty and had to be replaced.

switched the temp sensor with the other motor and still had the same problem both thermostats are new. i will check the ground and was gonna try making a jumper grounding the temp sensor wire directly to see if it is the temp sensor. I put a timing light on it and when it is in cold start the timing is jumping around from about 2degrees btdc to like 4degrees atdc then whin it idles down it runs perfect at 6degrees atdc.

bypassed the switch and she idled right down then plugged the switch back in and it worked perfect:banghead:! Guess it was a bad connection! does anyone know if the brown wire goin to the switch is a common ground and if that problem happens again if it wouId hurt to hook it straight to ground or bypass the switch all together. I appreciate all the feedback and love this website!!

bypassed the switch and she idled right down then plugged the switch back in and it worked perfect:banghead:! Guess it was a bad connection! does anyone know if the brown wire goin to the switch is a common ground and if that problem happens again if it wouId hurt to hook it straight to ground or bypass the switch all together. I appreciate all the feedback and love this website!!

Here's how I read the electrical diagram.

The brown wire is a sensor signal wire common to both sensors, not a common ground. When the brown wire is grounded, it signals an overheat condition and the powerpack should put the engine in SLOW mode, defeating the QuickStart system. The black/white striped wire is the temperature sensor that the powerpack monitors to determine that the engine has warmed up enough to drop the QuickStart-elevated idle speed. Port-side temperature sensor is the only one with a black/white wire on my looper.