Mercruiser RPM drops on shift and at idle

[jcox7483]

Hey guys, I've been reading the forum for a while now and I really appreciate all the info. you've put out there. Just got our first boat, 1998 Sea Ray 190 bowrider 8). The engine runs perfectly at speed but when I power down to a low 'no wake' speed or shift into idle the RPMs take a drastic drop before recovering. It wasn't a problem on the lake because I could give it enough time to recover. Around the docks it's a different story. When I need to shift from forward to reverse I ussually can't wait for the engine to recover and it will sputter out. Also, the shift from slow to idle will sometimes cause it to sputter and knock off. I am assuming that it is something that can be fixed with the idle set screw but I have a classic Camaro with a similar carb that doesn't behave the same way. I would have guessed that a problem in the idle adjustment would cause it to choke off everytime, not just drop RPMs and then catch back up. If you guys have any advice I would really appreciate it.

Sorry for the longwinded post...

 

[Don S]

Re: Mercruiser RPM drops on shift and at idle

It's normal,To a point.
I assume you have a Mercruiser Alpha I drive, correct?
If so, the drive as a dog type clutch and to get it out of gear there is a shift interrupt switch which will kill the ignition for a split second when shifting from fwd or rev to neutral. Without that, it would be very difficult to get it out of gear.
Now, if it stays on too long, then it causes problems like the engine dieing. That is usally caused by a faulty lower shift cable.

 

[jcox7483]

Re: Mercruiser RPM drops on shift and at idle

Yes, Alpha I hooked to the carb'ed 5.0 Merc. I'll look into the shift cable, thanks. It seems to drop much lower than my friend's boat. He has the 6 cyl. though so that may be the only reason.

 

[jcox7483]

Re: Mercruiser RPM drops on shift and at idle

Just in case anyone else has this type of problem; I spent a long time trying to figure this out but before I could start working with the carb. I replaced the battery. Turns out my battery was bad (bad cell I think) and didn't deliver very much amperage. Since I hooked it up to a charger it would start the motor (then the alternator would keep it charged enough for restarts). It didn't have the power needed to keep the thing running when the shift cut into the ignition.