merc 470/170 warm idle dies please help experts

mdoll1

Recruit
Joined
Jul 4, 2005
Messages
3
I have a merc 170 that runs good when first started but after it heats up and it seems the engine gets extremely hot (is that normal) you can only place your hand on it for a few seconds after 20+ minutes driving and at this point I try to idle wether in gear or neutral it dies. I owned it a few years and this seems has been a maybe been a reoccuring problem but have sat long enough that it starts up and off I go. I have not really noticed it as much in past. about my gauges the temp gauge says about 160 degrees when this happens and the tach says I am idling about 800. I know neither of these may be right but may help one of you bright guys help troubleshoot. Now I have not but in process of changing points and setting dwell and timing but have not started yet. I know it is alittle off due to backfiring, but I dont think that is the main problem. I am thinking about two areas the impeller in lower which I have not changed for a few years or the idle is set to low it sounds like the idle is extremely low but the gauge reads as I noted above. I am pretty sure it is not the shift interupt switch. any ideas.... think i am headed in right direction. I have never done an impeller and was thinking of trying it but my father in law heard it is a nightmare. any input like how hard and how long and what I should make sure I need to do if I try it would also be appreciated thanks alot guys!!!
 

Bt Doctur

Supreme Mariner
Joined
Aug 29, 2004
Messages
19,344
Re: merc 470/170 warm idle dies please help experts

impellers are good for 2 years max, the motor shouldnt be that warm. they are fresh water cooled and run about 170ish.backfiring could be a bad riser allowing water to get to number 4 cylinder.
 

yoced

Petty Officer 2nd Class
Joined
Oct 8, 2003
Messages
142
Re: merc 470/170 warm idle dies please help experts

Set your timing first. Remember to check your advance timing also. Bad timing and advance can cause you to run too hot.<br /><br />But it is also likely that your impellers are toast.
 

mdoll1

Recruit
Joined
Jul 4, 2005
Messages
3
Re: merc 470/170 warm idle dies please help experts

impellers? more than one or just one in outdrive?
 

Haut Medoc

Supreme Mariner
Joined
Jun 29, 2004
Messages
10,645
Re: merc 470/170 warm idle dies please help experts

No, just one. It's not that hard to change it. Try the 'search'option at the top of this page, look under 'impeller', or better yet 'Alpha 1 impeller' you should be able to find out alot especially from some of the links inside them..J
 

Stings

Seaman Apprentice
Joined
Apr 27, 2004
Messages
40
Re: merc 470/170 warm idle dies please help experts

would this be a merc 470? if so did you upgrade it to the 4" heat exchanger or still got te 3". you might want to upgrade to the 4". i had to replace my inpreller every year.
 
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