Mercruiser 165 4 cyl rough idle

[tonto340]

Hey all, thanks in advance for any info, Newbie to boats so any help appreciated!!!
Just bought a boat w/ a 87 mercruiser 165 4 cyl. Starts up good first turn of key. It will idle good for a little while in neutral but If you let it sit for a little while (2-3 min or so) the idle gets a little rough, sounding like it wants to stall until it actually does. It also sounds rough when idling in forward in wake zones and will sometimes stall and require a choke to restart. One time it stalled and when I went to start it wouldn't start and required a full on choke to restart and while trying to restart wouldn't make any sound like it wanted to start until full choke.
Will go fine after choke with just a small rough idle. When out on lake and cruising everything is peachy. I shut the boat off after tuber/skier and starts up fine, not rough at all. But then while idling back into dock (5 min down canal) will be rough again and usually stall at some point requiring choke to restart. All I've done with my small knowledge of engines is clean carb and change plugs, to not much improvement. Thanks again!

~Nate

 

[libellav15]

Re: Mercruiser 165 4 cyl rough idle

hi nate

new fuel and filters and water seperator - including filter in carb

dizzy cap, rotor, points and condensor (if relevant)

then set timing and carb screws - mixture and idle

hope it helps


cheers

adam

 

[tonto340]

Re: Mercruiser 165 4 cyl rough idle

Ok so i'm waiting on those parts, ordered from local marina, but a new issue to report. I took it out today and WOT was 4200rpm which is low on the spectrum of what it should be. Also while cruising it was bogging down like I throttled down but didn't touch the throttle. Then it would pick back up to where it should be. Related? different? thanks again!!!

 

[solar7647]

Re: Mercruiser 165 4 cyl rough idle

Ok so i'm waiting on those parts, ordered from local marina, but a new issue to report. I took it out today and WOT was 4200rpm which is low on the spectrum of what it should be. Also while cruising it was bogging down like I throttled down but didn't touch the throttle. Then it would pick back up to where it should be. Related? different? thanks again!!!

Sounds like you are getting an arch. Check your plug wires, or just change them. I had the same issue when I first bought my boat, new wires fixed the issue. I found out the hard way it was the wires though! Touched them at got a wake up call.