merc 90 hp 1970's

[reeldutch]

today i picked up a inline 6 cylinder 90 hp Mercury.<br />i know this motor was running 2 years ago.<br />because i started it for my brother in law and i checked the comp and it had 5 good cylinders and one was 80 psi.<br />for the 2 years inbetween the motor just was sitting there doing nothing.<br />we tried to start it yesterday but the starter motor didnt engage the flywheel.<br />my question is : is it worth to put some time and money in this thing or should i part it out?

 

[andrewkafp]

Re: merc 90 hp 1970's

You need to find out why you have 80psi in one cyl.Does the motor turn over with the plugs out?<br />If there was water entry in that cylinder, it may have seized up. The starter not engaging is a seperate problem and would be electrical, ie battery or solonoid.

 

[highaltitude]

Re: merc 90 hp 1970's

the starter is a separate prob. but the real prob is that the inline 6 cannot run on todays fuels. i am not an total expert-but i do know you would be wasting money running that motor with todays fuels.

 

[andrewkafp]

Re: merc 90 hp 1970's

It will run on unleaded petrol with no problems as long as it's above 89 octane. I'd say 85% of iboats members on the Merc forum have a pre-1980 motor about 1/3 are inline 6's and they are all still running... Clams.... where ARE you ????

 

[reeldutch]

Re: merc 90 hp 1970's

I am woried about the 80 psi cylinder.<br />when i have the starter going and run the motor i wil try a decarb with seafoam it might help loosen the rings??<br />if not will this motor be destroyed soon or can i use it for a few years?<br />if it runs and the compression wil not be a problem i hope the lower unit wil drop so i can do the waterpump. also i think i wil clean the carbs.<br />lot of work on an old lady.<br />i hope she's worth it?<br />how do people like these motors?<br />are they dependeble?<br /><br />thanks reeldutch

 

[Fishin4fun]

Re: merc 90 hp 1970's

If you are interrested in a 142-148psi complete bolt on powerhead for your motor, let me know, it will be a heck of a lot cheaper than even thinking about rebuilding the one you have, and you will be able to use what you have as a parts motor or as an anchor! Let me know if you are interrested. I have a complete powerhead ready to bolt up just sitting in my garage taking up space!

 

[reeldutch]

Re: merc 90 hp 1970's

no thanks i just want to get this motor running and see if it will run nice.<br />i dont want to spend too much money and time on it. i want to give it a tune up and maybe that might work.<br />i just would like opinions of people who own these monsters and if they like them?<br /><br />thanks reeldutch

 

[Fishin4fun]

Re: merc 90 hp 1970's

I have one and I love it, if I thought I was going to have any problems, I would keep the extra powerhead as a backup or spare. I have never heard of anyone that maintained one of these motors or that had one that ran properly give anything but positive comments about it. These motors are all but bullet proof, as long as you take care of them and do proper maintainance and preventave maint. Such as ensuring you are using good high octane gas, proper oil mix with a quality mix oil, change the impeller every other season, tune up every couple of years or as you notice the motor not performing as it should. Keeping the propeller in good shape. Stuff like that.

 

[reeldutch]

Re: merc 90 hp 1970's

ok i'm gonna give it a chance and put some time in this thing. i just hope that that lower cylinder compression are sticking rings but i think the rings are broken. <br />we will see soon.

 

[reeldutch]

Re: merc 90 hp 1970's

today i charged the battery and cleaned all the connectons. the starter did turn over the flywheel.<br />bud it didnt want to start.<br />i checked the spark and all 6 plugs have spark.<br />wat kind of plugs should i use?<br />than i sprayed some 25:1 premix in the carburator troaghts and id cranked up rightaway.<br />may be the fuelpump is defect?<br /><br />reeldutch

 

[reeldutch]

Re: merc 90 hp 1970's

the ignition switch of the controlbox is toast<br />were can i find a new one?

 

[Clams Canino]

Re: merc 90 hp 1970's

The I6 will run on todays fuel. Set max-advance to 21 degrees tops. <br /><br />Use a can of mercury power tune to free any stuck rings.<br /><br />You need to choke / almost flood them to start - no surprise there.<br /><br />Switch at West Marine - u neend to solder and adapt it in, Use wiring diagram.<br /><br />-W

 

[Fishin4fun]

Re: merc 90 hp 1970's

i've got a spare control box with power tilt/trim switches let me know if you are interrested.

 

[reeldutch]

Re: merc 90 hp 1970's

where can i find a wiring diagram to solder the wires back in?

 

[andrewkafp]

Re: merc 90 hp 1970's

You really need a manual to find most of the info you need like plug type and wiring etc. I have a set of .pdf's for the "Mercontrol" with the black choke button on top. It has the wiring layout and <br />photgraphs of what goes where.<br />You can e-mail me at andrewkafp@yahoo.com.au and I will reply with the info.

 

[Fishin4fun]

Re: merc 90 hp 1970's

the SELOC Manual, has breakdown of about a dozen different ones. I would recommend that manual for these motors. Very thourough and complete for most repairs and services.