1979 Mercury 80hp Thunderbolt

[A1an]

We have recently acquired an '79 Avon SR5.4 with a '79 Mercury 80 Thunderbolt, before starting on the boat transom we made sure the engine was a go'er, it turns out its been 10 years since it last ran!

To start with we replaced water pump, fuel pump, plugs, fuel pipes, carbs rebuilt and gave it a general tidy up replacing some of the wiring due to a bad earth to coil 3. The control box was also treated to a strip down, clean up and new IGN barrel and battery leads

Tonight it fired up great, idle was a little high but it ran lovely, I mixed up a slightly oily mix to run it on after lying for so long.

When we tried to give it a little rev and it didnt like it, it started missing and generally not wanting to rise, finger points towards the exhaust gasket and plate, we have water getting into the cylinders.

Now where did I put those sharp drills and tap and die set!!

 

[sutor623]

Re: 1979 Mercury 80hp Thunderbolt

We have recently acquired an '79 Avon SR5.4 with a '79 Mercury 80 Thunderbolt, before starting on the boat transom we made sure the engine was a go'er, it turns out its been 10 years since it last ran!

To start with we replaced water pump, fuel pump, plugs, fuel pipes, carbs rebuilt and gave it a general tidy up replacing some of the wiring due to a bad earth to coil 3. The control box was also treated to a strip down, clean up and new IGN barrel and battery leads

Tonight it fired up great, idle was a little high but it ran lovely, I mixed up a slightly oily mix to run it on after lying for so long.

When we tried to give it a little rev and it didnt like it, it started missing and generally not wanting to rise, finger points towards the exhaust gasket and plate, we have water getting into the cylinders.

Now where did I put those sharp drills and tap and die set!!

Aw man sorry to hear that for you. The block is in good shape?

 

[A1an]

Re: 1979 Mercury 80hp Thunderbolt

Yeah, it all looks good.

the serial# 9217662

where can I find part numbers for the exhaust plate and carb rebuild kit?

 

[carholme]

Re: 1979 Mercury 80hp Thunderbolt

That s/n is a Belgium made engine.

Parts Listing s/ns 9177626 thru 9256130:

http://www.crowleymarine.com/mercury-outboard/484.cfm

Gerry

 

[sutor623]

Re: 1979 Mercury 80hp Thunderbolt

Did you check compression also? I dont think this motor has a headgasket, so I agree, you may have a leak at the water input line at the exhaust gasket.

 

[Chris1956]

Re: 1979 Mercury 80hp Thunderbolt

Try not to break many bolts when removing the exhaust cover and inner water jacket cover. Pull the powerhead and lay it on the bench. Now use a torch to heat the bolts good and hot. Now remove the heat and spray with a good penetrating oul (PB Blaster is good). Let them cool a bit to suck the oil in. Use a hand impact driver to try to loosen the bolt. Repeat the heat and oil, if necessary and if your luck is good, you may get them out.

P.S. It makes sense to give some money to your local church, before your start the work. Devine intervention is usually necessary.

 

[sutor623]

Re: 1979 Mercury 80hp Thunderbolt

Try not to break many bolts when removing the exhaust cover and inner water jacket cover.

Hahaha, I like the way you put that!

 

[A1an]

Re: 1979 Mercury 80hp Thunderbolt

Its off, all done without removing the powerhead, the manifold gasket cover came off with 1 sheared bolt, unfortunately the shround/cowl around the flywheel and down around the head didnt want to have its bolts undone, 3 sheared on that but it was easily sorted on the pillar drill.

It all looks good inside, the block is good and the rings are fine, not bad for a 33 year old engine.

Hopefully this will be the last of the jobs on it.

Lucky really seeing as Im an atheist, a non prophet organisation!