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suposedly "seized" mercury 150 hp EFI 2001

coreymon

New member
hello

i have a friends 2001 mercury 150 EFI. last year the boat went out for the second run of the year just after the lower unit was replaced. the engine stopped about 50 feet from the dock. it would not turn over and i was told it was seized. i was not there but i have been told that it would not turn when they tried to hand start it with a rope. the boat has sat on the trailer for a year and today i took the crank cover off and i was able to turn the crank by hand. i turned it a few times and then it got tight and now will turn about a quarter revolution and then stops. the plugs were removed last year and some oil was squirted into the piston chamber. the prop and prop shaft was remover last year as well. what should i do next? i am thinking i should pull off the head covers. any suggestions will be welcomed. if i can turn the crank could it be that only one of the pistons is seized? can you replace just the rings and a piston or do i have to get the thing board out and replace all of the pistons?

thanks
 
Re: suposedly "seized" mercury 150 EFI 2001

Remove lower unit and see what happens when turning crank.-----------If still stuck then remove heads.-----------------If you see problems then dismantle engine.-------------Inspect internals and then see about price / availability of parts.
 
Re: suposedly "seized" mercury 150 EFI 2001

the lower unit is off. i can spin the crank by hand almost one full revolution but it comes to a certain point and stops. is this indicative of one bad piston? if i take the head covers off how will i know what is making it stick?
 
Re: suposedly "seized" mercury 150 EFI 2001

It is something " bad "-------------------Heads have to come off anyway !!-------Entire engine will have to come off the exhaust housing and be taken apart.
 
Re: suposedly "seized" mercury 150 EFI 2001

You have to pull the heads -----------------This looks " bad "--------------------There will not be a cheap / magic cure for this !
 
Re: suposedly "seized" mercury 150 EFI 2001

i know this will be an involved maneuver and cost plenty. i understand that this is a major mechanical malfunction. do you have any advise for a newbee doing a tear down like this? i have taken a power head off of a 75 merc before to change a gasket. i have a full shop manual, however this will be my first time removing heads/ completely dissembling an OB....
 
i will be taking head covers off tonight. any advise on removing all of the painted over bolts? do i need to knock the paint off before i put the socket on so it does not slip and round off the bolt head?
 
i was able to get the port head cover off before the rain started. the middle piston is shot. piston is crumbling/ has a crack in it. what causes this?
SANY0026.jpgSANY0027.jpgSANY0030.jpgSANY0031.jpg
 
starboard side is off and that side looks fine. i can spin the crank freely now. my guess is the chunks of piston from the port middle were hitting the head cover causing it not to make a full rotation. the port middle cylinder is very rough. next step will be to pull the powerhead.

1st big question:
what do i do about the trashed cylinder? (i will have pics of the cylinder in the morning if needed)

huge thanks for the input...
 
If crankshaft and rods are good ( a big IF )---------It is common to bore out one cylinder and fit a new oversize piston.----------------Measure and inspect all internal part to see what you have !!!
 
here is pic of the cylinder wall damage. all wires/ tubes are disconected and i am tring to find a lift to take the power head off...
SANY0037.jpg
 
It may clean-up with a rebore ------------------You need to find the " smoking gun " that caused the failure !!!---------------Carefully inspect all of the fuel system.-------------------If there is too much damage you may need a sleeve installed to go back to a standard piston.
 
You can't clean that damage up.You will need to resleeve, and oversize piston.
But first check crankshaft journal for damage...


Cause:

Detonation
Detonation occurs when two flame fronts collide. It is similar to pre-ignition in that a hot spot ignites the fuel BUT, at the same time (or close to it), the spark plug also ignites the fuel mixture and these two 'flame fronts' move towards each other and collide. This noise can be heard as 'pinging' or 'knocking' when accelerating in a car up a hill or passing (it can't be heard in an outboard motor because normal operational noises are louder and hide it). In fact, the octane rating was specifically derived as a measurement of a fuels ability to resist or prevent detonation and it's called the Anti-Knock Index (AKI). The higher the AKI (or octane rating), the more stable the fuel thus preventing detonation. While this pinging or knocking sounds harmless enough, you have to remember you're hearing this noise outside the engine. Given that you can't even hear the violent ‘normal' explosion occurring inside a gasoline engine, imagine how much more violent the explosion is if you can hear it as knocking behind the dash of your car. When these two flame fronts collide, it's equivalent to a sledge hammer being dropped onto the top of the piston, and it's easy to see how this situation might manifest itself into engine failure. Like pre-ignition, detonation raises the combustion temperature considerably, but more notably often cracks the piston, breaks rings and ring lands, and can bend rods.

Steve
 
Detonation in a 2-cycle outboard engine somewhat resembles the "pinging" heard in an automobile engine. It can be otherwise described as a tin-like "rattling" or "plinking" sound.

Detonation generally is thought of as spontaneous ignition, but it best decribed as a noisy explosion in an unburned portion of the fuel/air charge after the spark plug has fired. Detonation creates sever, untimely, shock waves in the engine, and these shock waves often find or create a weakness: The dome of a piston, piston rings or piston ring lands, piston pin and roller bearings.

While there are many causes for detonation in a 2-cycle outboard engine, emphasis is placed on those causes which are most common in marine 2-cycle application. A few, which are not commonl understood, are:

1. Over-advanced ignition timing.

2. Use of low octane gasoline.

3. Propeller pitch too high (engine RPM below recommended maximum range).

4. Lean fuel mixture at or near wide-open-throttle.

5. Spark plugs (heat range too hot -- incorrect reach -- cross-firing).

6. Inadequate engine cooling (deteriorated cooling system).

7. Combustion chamber/piston deposits (result in higher compression ratio).

Detonation usually can be prevented, provided that:

1. the outboard engine is correctly set up and

2. diloigent maintenance is applied to combat the detonation causes, listed, preceding.

Steve
 
thanks for the input. as far as i can tell the jury is still out on what the "smoking gun" is. the powerhead is removed and i will begin tear down soon. we will see...
 
21 foot Logic model 210cc. prop is stamped 48-832832-c1-21. this boat and engine were purchased new from a Logic dealership in ohio in 2001. since that time each winter it was winterized and stored at beaver park marina in Lorain OH. the lower unit was replaced by that marina right before this failure
 
You need to ask them what is gear ratio....Or look at top of plate on lower unit is what number is on it, like 12 etc
how much time did you have on lower unit before motor let go.Plus why was lower unit replace, was it rebuild, or new or after market

Steve
 
i was told the lower unit was replaced under warranty due to bearing problems. i do not know if it was rebuilt. the boat ran for aprox 1hr the first day in the water after the new lower unit. the next day it stopped 20 feet from the dock. i will not see the lower unit again for a week or so. the power head will be near by later this week...

does anyone have a sugestion on where to get a remanufactured PH? i have seen them for around 4,000.00 is there any way to do it cheaper? assuming i can not rebuild this one.
 
just talked to the person who was running the boat when it died. he stated that he heard a loud knocking noise then it died. they restarted it and the noise was louder and then stopped.
 
today i was told by the boat owner he filled up the tank with the cheapest fuel at a automobile gas station prior to this event. if that can cause this kind of damage on this particular engine what is the lowest grade fuel that should be used on this?

ph is on a bench now the tear down starts sat...
 
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