Semi seized 120hp Johnson

"Hello, I have had this engine

"Hello, I have had this engine rebuilt recently,only done 20min running, and when i took it to a mechanic to have it checked out because it was not starting properly[not the person that rebuilt the engine] he has done the compression check and all were fine,he did a tank test and the thing stopped after 5 mins running at 1800 rpm , he them rang me to tell me that the engine had seized,and to take it back to the engine rebuilder which i did ,the second mechanic had used his own fuel which on taking a sample has turned out to be very poor quality,small amount of water and sand smells like turps,it has made rather a large score up the inlet side about 4mm wide and 40mm long not really consistant with the lack of oil in the fuel i do think there was some in there but how much i dont know, is it possible that a ring has broken, maybe denotated with this old fuel and caused this, there didnt seem to be much of a hone mark in the bores for 20mins running not sure if he did the the ring gaps either could someone guide me on this one thanks."

"Joe just reading one of your

"Joe just reading one of your replys on another issue earlier talking about removing the thermoststs which could cause piston scouring on the cyl bore on my engine they have removed the themostats and choked them because they said it would keep the engine cooler ,is this correct ."

Removing thermostats is a mist

Removing thermostats is a mistake.The piston grows in diameter due to the heat.If the cast iron cylinder sleeve stays cold it may not give the piston enuff clearance.The cylinder would grow ( half the expansion rate of aluminum )if it warmed up.

"If possible post some pics of

"If possible post some pics of damage., might be easier to evaluate.
As any correctly rebuild engine should run a 'double oil' run-in time (VRO plus 2% in fuel), I doubt some lousy fuel might be the cause, unless some oil has been forgotten!
If the re-builder is the same that messed up Your thermostats, I doubt he is quite competent."

"Morten thanks, yes he is, he

"Morten thanks, yes he is, he says he dosent put the thermos in just chokes them maybe Ikia has a point may have grabbed a ring"

"In total agreement with Morte

"In total agreement with Morten. Thermostats are an essential component in those high performance engines, and for the same reason that they are required in all automobiles.

(Thermostat Purpose)
(J. Reeves)

Many engines are considered high performance engines and demand a thermostat(s), and many smaller hp engines also require a thermostat for the following reason. The pistons actually distort/twist off round when running. The thermostat is required to keep the outer wall surrounding the steel cylinder, and the cylinder wall itself at a temperture to compensate for the distortion.

With the thermostat removed, the difference in temperture between the inside the cylinder and the water jacket quickly reaches a point whereas (in effect) you have a oblong piston running up and down a round cylinder, or vice versa. Bottom line is without the thermostat, the piston and cylinder wall could be damaged in a short period of time.

The thermostat in your car isn't there simply to have the heater function properly..... think about it.

When time permits, visit my store at: http://stores.ebay.com/Evinrude-Johnson-Outboard-Parts-etc?refid=store

Sounds like there may be a visit scheduled in the near future to the small claims court.

The second mechanic that was running the engine when it seized..... as Morten suspects, was he somehow running your engine on straight gasoline, that is possibly completely without oil?"

"Joes thanks ,i have yet to do

"Joes thanks ,i have yet to do a test is there some quick way without sending it off to be tested like pouring some onto a piece of cardbord to see if there is any residue oil remaining ?"

"A plain white sheet of paper

"A plain white sheet of paper is best. Pour some of the known gasoline on it that the engine was running on when it seized.... best to get it straight from the brass drain plug at the front bottom portion of one of the carburetor's float chamber..... or all carburetors in separate tests.

If straight gasoline, the gasoline will evaporate, leaving the paper as it was originally.

If mixed with oil, the gasoline will evaporate BUT will leave a oil stain upon the paper.

Have reliable witnesses with you when you perform this test for future references.

Keep in mind that the carburetors feed in a "X" (crossover) configuration. That is, standing in the boat, facing the carburetors, the top port carburetor feeds the top starboard cylinder, etc."

Thanks Joe i will keep you pos

Thanks Joe i will keep you posted thanks again to all posts