1983 ISH Mercury 175 v6 problems

We brought this 175 v6 mercury on a speedboat and didnt hear it running but got cheap , when we got back and put freash petrol in her and a new battery after 2 clicks boom she started , running lumppy and knowing that she had been sat for 2 years we put new leads and plugs in her . started up on the button but still a little lumppy ( missing a little) revs fine .. so we put her in the water today hoping that a nice blast would clear her out , NOPE as soon as we were in water , in gear and revs at full wack we were doing 3-4 nots max ???? please help .

Re: 1983 ISH Mercury 175 v6 problems

First check compression and for spark on all cylinders. Do a search of this website and you will find the procedure if necessary. With a 2 year sit and the boat new to you, drain the fuel tank (bad old gas with water in it?) and replace all the old fuel lines, fuel filters and primer bulb to eliminate air entering fuel system. Take off the fuel pump leaving it intact and pump gas thru it with the primer bulb, if it leaks, rebuild the fuel pump. You should also clean and rebuild the three carbs with new gaskets, seats and needles. This is all basically maintenance that you need to do anyway since you just bought it and it may fix your problem. Also change the water pump impeller BEFORE you take it back out on the water. Post back your results!

Re: 1983 ISH Mercury 175 v6 problems

Thanks for the reply , we are going to check every spark today , and compression . would you know what psi it should be ?

thanks

Re: 1983 ISH Mercury 175 v6 problems

110-120ish, and fairly even, within 10%.

Re: 1983 ISH Mercury 175 v6 problems

Check oil injection is working.Also view plugs after a warm up,they can tell you a few stories.Did you inspect the old plugs.

Re: 1983 ISH Mercury 175 v6 problems

Hi all , Well the good news is she is fixed , the comprestion was good all beyween 130-146 , checked sparks and was missing on 2 so we brought new leads and plugs and still missing , so the got 2 new coils for them , still nothing .... but a mate of mine said check the switch box .... brought one for 50 notes and bang she was lovley on the water ... only thing is i need a fuel lorry behind me lol