Please help!!!! Early 70's Merc 80hp a lemon!!!

[MountainManMyke]

Hey guys, just wanted to say that I am extremely frustrated right now. I restored my 15ft boat which took me a year and a half. I purchased a I believe a 1972 Merc 80 hp with a thunderbolt ignition. When I took the boat out the first time it was exciting because it had taken me so long but the motor ran like crap. I figured no big deal... I cleaned the carbs and stuff. Motor ran abit better.... but still not 100%. I figured ill give myself a break and take it to a small engine mechanic and once he was finished tuning it up and replaced all new fuel lines, carb/fuel pump rebuild, tested spark under load...... I was billed 500 bucks and he said the engine has a ticking/clicking sound coming from the top of the engine which can be heard over the exhaust (the mechanic said it sounds like a crank bearing) and it idles really high and wont idle down, the idle is set to the richest. It might be because its sucking air from somewhere to cause it to idle like this. Please help me, I just dropped 500 into this motor and cant afford to buy another one. I am considering doing a rebuild myself, I am a truck mechanic by trade and can figure it out if I have the propper service manual but it will be super time consuming. Any advice on what the sound can be or why its ideling high? If I am forced to do a rebuild where can I get a manual and engine parts? thanks alot

 

[oldman570]

Re: Please help!!!! Early 70's Merc 80hp a lemon!!!

The top main seal could have a crack in it and let the crankcase suck air. It is not an uncommen thing to happen on older motors that have set for sometime. The ticking could be the upper main bearing not getting enought oil because of the air leak in the main seal or the flywheel going past the stator with rust buildup. A OME manual for that motor can sometimes be bought on Ebay or at a Merc dealer. Some parts can be bought new and others at salvage yards listed here in a "Sticky". A search at Oldmercs.com and Seaway marine will give you a good Idea as to whats around for new parts while some others can be bought on Ebay. A rebuild at some shops can cost around $2500 depending on location. The seal can be removed and replaced fairly easy and could solve the problem and the motor run for some time. The first thing I would do is get a compression check of the motor to be sure they are all within limits before doing anything else. Always use muffs with water to the LU and have the carbs at WOT. Be sure to ground out the plugs or wires to the block when the motor is being turned over or damage to the switchbox and other electrical can happen. JMO
Oldman570

 

[tpenfield]

Re: Please help!!!! Early 70's Merc 80hp a lemon!!!

40 year old motor . . . may just be worn out . . . probably not what you would call a lemon.

Probably not a good idea to have a marine mechanic work on an old engine like that, as the cost will tend to be more than the value of the engine, which you now know.

Starting with a compression test is a good idea, but the engine may just be ready for a rebuild.

 

[MountainManMyke]

Re: Please help!!!! Early 70's Merc 80hp a lemon!!!

I really appreciate the replies. it could very well be the flywheel with rust buildup because it was outside with the side cowlings off during a few rainfalls and it never made that sound before that. How would I try and fix that? Also, the high idle could be cause by a faulty choke because if it idles and I hit the electric choke button it will kick it down. the cylinders test all around 130-135 psi. I am hoping its just all minor stuff so I can get this thing going without a rebuild. tHANKS

 

[Chris1956]

Re: Please help!!!! Early 70's Merc 80hp a lemon!!!

The idle speed could simply be turned up. I assume it has distributor ign? The idle pickup timing s/b 4-6* BTDC and the max spark advance s/b 21*BTDC.

 

[Chris1956]

Re: Please help!!!! Early 70's Merc 80hp a lemon!!!

Once the idle timing is set, and the carb adjusted, the idle speed is set to about 900RPM. A set screw is used for idle stop and the throttle cable pushes the throttle against the idle stop.

 

[MountainManMyke]

Re: Please help!!!! Early 70's Merc 80hp a lemon!!!

where should i look for the rust buildup with the flywheel going past the stator? thanks

 

[oldman570]

Re: Please help!!!! Early 70's Merc 80hp a lemon!!!

Any rust should be between the coils and flywheel where they come into close contact with each other as the flywheel spins. Any marks on the flywheel magnets will be a indaction that the metal center on the end of the stator coils is hitting the flywheel and should not be. Removing the stator will let you check the condition of the upper crank seal. Be sure to use blue locktite on the stator screws, when replacing them, so they will not back out. A look at the wires and insulation of the coils on the stator will tell if the stator is in good shape and working. Any burnt or melted insulation on the coils will tell you that the stator could be bad or going bad. If everything there checks out then any noise you hear will be comming from inside the motor or LU and is being transmitted up thru the motor when running. Could be the rotor on the distribure going past one contact point on the cap making a ticking noise, or spark jumping from any place to ground.JM02
Oldman570

 

[Dave1027]

Re: Please help!!!! Early 70's Merc 80hp a lemon!!!

I was billed 500 bucks and he said the engine has a ticking/clicking sound coming from the top of the engine which can be heard over the exhaust (the mechanic said it sounds like a crank bearing) and it idles really high and wont idle down, the idle is set to the richest. It might be because its sucking air from somewhere to cause it to idle like this. Please help me, I just dropped 500 into this motor and cant afford to buy another one.

So you were handed back a non-working motor and billed $500 for your trouble? You got scammed by a phony boat mechanic.

 

[chum1]

Re: Please help!!!! Early 70's Merc 80hp a lemon!!!

not a lemon when new

 

[MountainManMyke]

Re: Please help!!!! Early 70's Merc 80hp a lemon!!!

so it turns out the loud ticking sound was my flywheel. I took my flywheel off and the plate it mounts to and discovered a hairline crack through it which caused it to make that noise. Now I just have to figure why its idling so high. Any recommendations? thanks

 

[Chris1956]

Re: Please help!!!! Early 70's Merc 80hp a lemon!!!

Mike, That motor looks to have some sort of reluctor-based trigger system in the distributor. Never have seen this before,I cannot advise on it. Maybe you should get a OEM service manual.