Lack of power - Merc 170

[rcspencer1]

1985 Merc 170 4cyl FWC. Engine revs up over 4000RPM at idle, but has hardly any power when put into gear. Did a tune up (points, cond, rotor, cap, wires - everything but plugs), but didn't fix problem. Next step will be new plugs, but in my years of fixing I'm doubtful that will help. Any thoughts? Thanks

 

[atomb]

Re: Lack of power - Merc 170

i have the same issue i think it may be the timing i reset mine and it was way off. i havent water tested it yet but im fairly certain that was my issue.

 

[Bifflefan]

Re: Lack of power - Merc 170

First, Welcome to iboats.

Second

Engine revs up over 4000RPM at idle

How is this possible?

If you mean it will rev in neutral, that means nothing. It will rev in neutral on 2 cylinders.

Start by doing a compression check and post the results.
Since you have already done a partial tune up, we can rule out those parts I guess.
Did you reset the timing? What is the dwell? When was the last carb overhaul?

 

[rcspencer1]

Re: Lack of power - Merc 170

Thanks for your help, and now that I look at it what I wrote didn't make sense. Not sure what I was thinking when I wrote that it revved to 4000 in idle... :>)

I appreciate what you're saying and am going to check both the timing and compression when I change the plugs.

Thanks again for your help - I really appreciate it!!