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Lost cylinder 3 and 4 on Mercury xr2 while at WOT.

L

llyons

New member
Hi, was out in the boat yesterday after recently getting some work done and spark plugs replaced. Before spark plugs 2 and 5 had gone bad per the shop. After replacing the boat was flying out of the hole and ran well. However on the way in at WOT, the motor died. After looking at the compression on each cylinder, cylinders 3 and 4 have 0 compression.

i know this basically means this motor is shot.

I have a couple questions.

What would suddenly cause both 3 and 4 to go out? both are middle cylinders. I can definitely see the pistons are moving in 3 and 4. Picture of 3 spark plug is below?

Also, this is an older 87 champion that I recently had re carpeted, reupholstered, new trailer, etc. I have 7k in the update

Am I better off getting the motor overhauled? Any thoughts on what that cost?

Is there cheaper or better alternatives then getting this motor overhauled? Perhaps a second hand motor from a motor exchange?

Looking for any advice and suggestions. Thanks in advance.


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Remove cylinder head and inspect.-----And 3 and 4 run off the middle carburetor.----Any issues in there could starve those 2 ccylinders of oil.-----And here we are.
 
Hi, went ahead and pulled the heads to see a little more. Here are some pictures. I am thinking that piston 3 melted from getting to hot. You can still see the rings attached so that part is good (maybe avoid more serious damage to cylinder walls. Number 4 looks like a ring gave out. I am no expert just guessing. I think I read that a piston can melt like this and it doesnt do damage to the cylinder sleeves?

Overall im guessing that it can be rebuilt. Am I wrong on this?

Can you tell from these pictures if it was an oil issue or over heat issue? There is oil injection is still connected and the reservoir is full. I can also see oil in the transparent fuel filter (bluish tint).


In terms of the oil perhaps missing in the middle carbs, how could that happen if the oil mix is done before the fuel pump and that all the carbs get fuel/oil from the same source?
It was mentioned that I should move to a 2.5L engine instead. Will that motor mount on top of the lower unit that I already have? Is the 2.5 significantly heavier than the 2.0?


I have a mechanic that does pretty good work and so I will bounce these questions of of him as well but just trying to educate myself as well.






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faztbullet said:
That preignition damage ,trigger,adavnce box or switchbox problems. Best to upgrade to 2.4 or 2.5L motor
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Would that 2.5 mount directly to the lower unit that I have or are you suggesting a complete new motor and lower unit?
I certainly dont want to buy a brand new engine and lower unit as the boat isnt worth that.
 
Check and see if oil pump still turns.----Inspect middle carburetor.-----Water pump impeller replaced every 3 or 5 years ?
 
anybody know what shops typically charge for this kind of rebuild?

Do most shops get rebuilt blocks from outboard motor exchanges or do it themselves?
 
Very few shops do their own rebuilds.-----Check for rebuilt block at Crowleys.----=--But remember you must find and correct what caused this or you will be doing the job twice !!
 
racerone said:
Very few shops do their own rebuilds.-----Check for rebuilt block at Crowleys.----=--But remember you must find and correct what caused this or you will be doing the job twice !!
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Ya i agree. With 3 and 4 having issues im guessing the center carb but not sure. If 3 went out would some of the piston find its way into 4 causing it to go?. Clearly 3 melted from heat it appears like
 
Not a carb problem......#4 could have sucked the aluminum back up exhaust due to the pulses
A 2.4 150 will bolt right up, a 2.5L you will need the 2.5L as block is wider but it will bolt up.
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