what does or would it cost to have a 50 mercury rebuilt completley and is it worth it ?

Depends on year and how many cylinders, and what you're going to have to pay for the parts, from the dealer they are very expensive.  Also depends on if you know how, do it wrong and it can be a whole lot of money down the drain.  If either of these fit, you would be better off getting a reman'd power head, just be dam sure you DO NOT  do any dealings with Black Bird, you WILL get shafted.

Pistons can cost you $150 each.

Boring cylinders can cost $50 - $150 each

Gasket set can run a couple of hundred.

This is what's replaced in a basic rebuild, Bearings are normally reusable and the cranks can't be turned.   If it runs a bottom roller bearing, you replace it but the needle bearings are usaully good.

If crank is bad, the motor is basically junk because it gets extremely expensive and they also do not consider a bad crank in one a rebuildable core and will not give much of your core charge back when you send it in.

1988 mercury 4 cylinder 50 horse that has had very minimal use maybe 3-5 times a year just enough ,,,im worried though that if i buy it and use it a lot ill have to rebuild it ???

if there isn't anything wrong with it why would you have to rebuild it. My dad has a 1978 35hp evinrude that runs like a top.

i havent bought it yet it just concerns me that its a 1987 model it has little run time and i wanting a worst case scenario,,,,the whole deal is too good to pass up for me im just wondering if the motor tears up what it oukld cost me

Do a compression test. That will tell you a whole lot.

If you are afraid of buying a used motor then don't.

If you can't afford a new one, then what choice do you have.

Anytime you buy a boat and a motor, you best always be prepared to invest some more money into it at some point.

Given the situation economically today, boats and motors are a great deal right now.  Lot's of folks selling them due to job loss and business turn downs.

what does a compression test cost ?

You can buy the tool to run your own compression test for about $20.

It is real easy to  do.

It is not one of those tools you will use very often, but can save you from buying into a lot of trouble.

Brute

i was wondering about that ,,,what tool do i buy i assuming its a pressure gauge of some sort

You can get the tool at any auto parts store.

You just remove a spark plug, screw the gauge into the spark plug hole and crank the motor over a few revolutions.

I'm not sure what kind of number it will read, but you do want every cylinder to be consistent.

Brute

like everyone said compression test that sucker ,are you able to take the boat out for a test? or at least run it off the hose for a long while and check your water output and for overheating .ask when the water pump was last done .my 1988 50hp merc runs like a top.just depends on what kinda life the motor had and by all means toss that oil mixer bottle (if it still has it) and pre mix the fuel by hand .the mixer normally stops working and the motor will seize.

1988 mercury 4 cylinder 50 horse that has had very minimal use maybe 3-5 times a year just enough ,,,im worried though that if i buy it and use it a lot ill have to rebuild it ???

Is that the 'Classic 50'?? If so its actually a 45hp and I would most deffinetly get it! They are great, and the smoothest running motor you will find. It also takes alot to wear one of them out. They are also very easy to find parts if you need any, and many can be found on Ebay.

it is a classic 50its on a bass tracker pro 17 everything works some years it was only ran once ot twice ,,,,he did say to get fuel pump checked,,,,it has a oil mixer that beeps if you dont have enough in yes !! the guy who has it said to have the fuel pump checked just as a precaution and that scared me + the motor is an 87 so its 22 years old but lots of people hav told me that it was a great motor to have

The are some much needed service items that will need done to the motor so price them and figure them into your cost.

Water pump, you can bet it hasn't been replaced in recent history, if ever at all.

Carbs cleaned, as much as that motor has sat, they will surely needed to cleaned to be reliable.

Fuel pump will need to be rebuilt.

Most of the fuel lines are probably old and brittle.  That older stuff doesn't handle the additives in modern fuels real well and it dries them out.

As for the motor's internal condition, that's going to depend on how it has been stored.  Motors left out so the early morning to mid-day sun hits them develope tremendous amounts of condensation.  When a motor is not run for long periods the oil film breaks down on internal parts like the crank and bearings, letting them rust.  When this happens the motor is pretty much junk.   Knowing it has probably never seen fogging oil when it was left to sit.

it has always been garage kept i know that and atleatst ran two three times a year ,,,,,,,im probably looking at adding anther 500 bucks to the motor