johnson v4 90 vro 1984 90hp

could annyone help me pls ive got a 1984 v4 90 vro on the last trip out it started to rattle then cutout the rattle came from what sounded like the bottom end after a few moments it started again but only for a few mins their was no smoke wen i baught it hom it ran smooth in a tub ime not shure what went rong pls could someone help thanks

Re: jhonson v4 90 vro

Remove spark plugs and take a compression reading of all cylinders. What are the readings.

Slowly and carefully remove the large slotted drain plug from the lower unit and check the magnet on the end of that screw plug for metal chunks, slivers, splinter like pieces of metal. Small fuzzy metal particles that you could rub between your fingers without doing any harm to ones self are okay.

Let us know what you find.

Re: jhonson v4 90 vro

thanks four your reply ive done the tests and its not good one of the pistons has no compresionat all all others are in the green took botton screw out and their was no sharp bits at all what to do next please help

Re: jhonson v4 90 vro

Make notes and take pictures so that you don't ned to rely on memory when reassembling any portion of the engine.

Remove the cylinder heads so that you can thoroughly inspect the pistons, cylinder walls, underside of the cylinder heads, condition of the head gaskets, and head and block (crankcase) sealing surfaces.

Also describe the condition and appearance of the spark plugs.

Let us know what you find, and describe your findings as good as possible.

Re: jhonson v4 90 vro

hi ive took the head apart the first part was the water housing whitch was coverd white salt after this removed head the pistons were dry and grey the bottom cilinder was realy dry didnt feel like their was anny oli or petrol in it the top cilinder was ok wet and fairly clean boath were slightly scored but after rubbing my finger rounde the bor seemed ok the sparkplugs were dry and a light grey the bottom one was alittle darker the head itself were not pitted or matked boath pistons were intact couldnt see the rings boath gaskits were in good order

Re: jhonson v4 90 vro

Very strange that at least one of the cylinder walls isn't scored bad. With absolutely no compression on one cylinder, there is usually serious damage to that cylinder's piston and wall.

Unfortunately, at any rate, you're looking at a major overhaul project, the cost of which can only be determined by tearing the engine completely down, separating the good parts from the bad and figuring their cost, figuring in the cost of carburetor kits, a new VRO (or converting to pre-mix), machine shop work, whatever else may be needed (gaskets, plugs, etc)............ this needs to be done before a acurate estimate or repairs could be made.

It may be time to move up to a later model engine.

Re: jhonson v4 90 vro

could the moter be rebord or is it just not worth the trubble as a moter this size is expensive to by