oil pressure test 9.9hp

Hello All,

I have the head off of my ob at the moment

Can anyone suggest a way of checking that the oil pump is working properly before i put the head, carb, exhaust etc back on?
I had an engine seizure whilst out on the water - not sure if it was due to drop in oil pressure or down to lack of coolant

i've taken the head off, the pistons and barrels are fine, no scoring at all, still a v nice fit for a 1998 motor

plugs were quite sooty ( but it is horizontal set up )
pee was fine when i left my berth

thoughts please

Many thanks Ian - London

Have you removed the cam and checked the bearings and journals there? That is the farthest component from the oil pump and is the one most likely to suffer/exhibit damage from lack of oil pump lubrication first. The pistons and cylinders are splash lubed so a pump failure probably wouldn't affect them nearly as much as it would the cam and crank bearings..

Checking the oil pressure is simply a matter of removing the oil "switch" and inserting a mechanical gauge. I can't find any documentation as to what the expected pressure should be but I would say no less than 10 psi cranking.....15 psi idling and 25 psi at 2000 rpm.

Good luck.

Are you really sure that the pistons and cylinders are splash lubed ?-------I am quite sure that oil pressure is needed for them too !

Well I don't have documentation for the VERY latest of this series of engine and he didn't say what year his is but yeah, most, if not all, of these smaller twins are splash for piston and pin. IE: no drilling through center of rod core and no nozzle for piston crown cooling. Although, it could be argued that the term used should be "sling lubed" as this is not a "crank in sump" arrangement and the crank pin holes rotation provides the "impetus" for the oil to find it's target.

That's why, if it did indeed seize up on him, and he sees no cylinder damage, it is very likely a lack of oil pressure problem and not an overheating one. I think it it is also likely to have scored bearings and journals and they should be inspected.

But, then again....I've been wrong before. So, if you have better information for him, please share it.