mercury 70hp

[DJENAN]

i have just bought a boat with a 1978 mercury and have since been told that they are really bad for corrosion, is that true? Also does anyone have a manual in electronic form for this motor?

 

[andrewkafp]

Re: mercury 70hp

Dunno...<br /><br />All Outboards are prone to a bit of galvanic corrosion. You can search here for posts relating to this subject. It depends on how the motor has been treated. I have an '81 Merc that has no real problems with corrosion. The L/U has been off recently with no issues. If your motor has been neglected ( Not flushed after use ) rarlely cleaned or lubricated, or Zinc tab missing.. it may have some corrosion. Look for broken wires that are still covered, but all green and fragile underneath.Look for a whiteish powder around components and just poke them with a screwdriver to see if it's only surface or right through.<br />BTW You won't get an electronic manual.. but you borrow the Clymer from your library and do what is neccesary to solve your problem <br />They are about 90 bucks to buy here in OZ.

 

[DJENAN]

Re: mercury 70hp

thanks for your for your prompt reply, i checked my zinc plate and it only has minor pitting on it, so would that indicate the engine itself probably only has minor corrosion?<br />Also where can i order a manual?

 

[DJENAN]

Re: mercury 70hp

also my motor was sitting unused for 2 years when i bought it and wasnt fogged, is that bad?. i have had the carbs cleaned out and it runs good apart from stalling at very slow crusing speeds/idling intermittently. Compression is 145psi on all 3 cylinders. You mention lubrication, what parts should i lubricate apart from all the grease nipples i noticed everywhere?

 

[andrewkafp]

Re: mercury 70hp

Don't know whether you can measure the corrosion by the condition of the tab (Could've been replaced) but at least it has one.. <br />145psi is good for that motor. Make sure you keep and eye on that telltale (pee er) as water pump impellers are the main topic re-outboards as you will find on here. It should run strong and not too hot to touch at high speed. Use WD40 liberally around your motor,(All moving parts) check the wires going to the switchbox for decay under the plastic covering.If they are corroded, strip them back and join with similar AMP auto wire and re-cover.<br />Manuals are a bit pricey, but neccesary.<br /> http://www.computeroutpost.com.au/tco/item.asp?code=CB726 <br />Have a search around iboats and www.outboardrepairs.com for Do's and Dont's with your motor. There are some basics to stick to, which will keep you out of trouble.

 

[andrewkafp]

Re: mercury 70hp

Have a squiz here...<br /> http://www.screamandfly.com/home/engine_tech/galvanic_corrosion/galvanic_corrosion.htm

 

[DJENAN]

Re: mercury 70hp

thanks for the info, good link on corrosion!!<br />is it possible that my compression might be high because there is too much carbon build up on the pistons etc. <br />And does anyone know how to clean out the carbon or decarb ?

 

[andrewkafp]

Re: mercury 70hp

Your compression is not high.. It's good. It has probably done little work and has good rings..<br />You can buy a product from Marine shops made by Quicksilver that you spray through the carbs.. Very smokey though.<br />I have never de-carbed, but it is a widely practised activity on 2 strokes. Do a search on here under decarb and there will be heaps on it.

 

[DJENAN]

Re: mercury 70hp

wow thanks for all your help guys!! much appreciated!!

 

[werdna]

Re: mercury 70hp

Quicksilver PowerTune its called

 

[Troy_from _Oz]

Re: mercury 70hp

anyone know how powertune differs from standard auto carb cleaner that you spray through the carbys also?<br /><br />I think golden seal also do aftermarket repair manuals too - but are similarly priced to the one unicorn mentioned.<br /><br />Cheers<br />t

 

[andrewkafp]

Re: mercury 70hp

Just a bit of feedback on your comment about "Really bad for corrosion". Upon reading through relative posts, it seems that Mercs from the 70's and early '80's did have a problem with water jacket leakage caused by corrosion. This can mean that water can leak/drip "around" but not neccesarily "out of" the spark plug holes.<br />If this happens, you can clean them up and put some "Quicksteel" putty in there. Will withstand 260deg c.. and may not re-occur. Or, if the leak is more seroius or you find it to be leaking from the head (inside cylinder), you have to remove the powerhead, remove the water jacket and head and assess the damage. You can either weld, or replace parts.<br /> http://www.afcinternational.com.au/myweb/products/quiksteel_repair_plastic_tech.htm <br />Compliments of Troy from Oz

 

[DJENAN]

Re: mercury 70hp

good idea troy, i have used that quicksteel stuff to seal a hole on my intercooler on my car and it worked well.