Bought a used 6 hours outboard but forgot to add engine oil

[fairdeal]

Whats the normal oil pressure? In idle and wot? Is there a table by RPM? Thx

if it has not changed from earlier models -
as of the 2010 SM -

pressure at idle - engine warm,10-W30 oil, should be 28 PSI or more
at 3000 rpm, 65 PSI or more

the oil pressure switch is satisfied - opens - between 4.3 - 8.5 PSI

[TownsendsFJR1300]

Much lower oil pressure would indicate larger clearances (major wear-to bearings) once running.

For the piston rings / top end, a leak down test would show any measurable wear right now, not running.

The oil pump very likely had residual oil in it and hopefully survived..

[Yamaha18]

would it help if I dropped a couple drops (using needle oil bottle dispenser) of 4 cycle oil into the 4 spark plugs before I fire up the engine after connecting the kill switch clip?

I know it would help 2 stroke outboard to start easier if add fuel/oil mix into the spark plugs just unsure about the 4 stroke with fuel injection?

Thanks for all your help so far.

2 things to do before I fire start my poor F70 outboard: (1) add 2 drops of oil (2) compression test of all 4 cylinders (was told should have at least 170 psi)

will let you know today after I start up the outboard.

[TownsendsFJR1300]

It won't hurt anything to add some oil.

If anything I'd add the oil just to get oil back on the cylinder walls, etc.

Cold starts, oil back in the crankcase causes the most wear (under normal conditions)


Just know that adding oil WILL hide piston ring wear and result in more compression (than if started "dry").

With the leak down test, there's NO cranking over, just getting to TDC on the compression stroke..
I would add the oil, spin it some (safety lanyard out so it doesn't start) and crank it some to get oil everywhere.

Then crank it up, and after warm, do your compression test..

[Yamaha18]

It won't hurt anything to add some oil.

If anything I'd add the oil just to get oil back on the cylinder walls, etc.

Cold starts, oil back in the crankcase causes the most wear (under normal conditions)


Just know that adding oil WILL hide piston ring wear and result in more compression (than if started "dry").

With the leak down test, there's NO cranking over, just getting to TDC on the compression stroke..
I would add the oil, spin it some (safety lanyard out so it doesn't start) and crank it some to get oil everywhere.

Then crank it up, and after warm, do your compression test..

thanks for the tips - this really helps

[TownsendsFJR1300]

Any updates?

[Yamaha18]

Any updates?

YES, bad news. I dropped a couple of 4 cycle oils as I mentioned and cranked the engine three times without inserting the kill switch clip to make sure the oil will spin around in the 4 cylinders. I then inserted the kill switch clip and cranked start the F70. It started with only 1 crank, so miracle #1 happened.

I hear the engine ran but with very slight knocking sound, no overheat alarm with running for about 20 seconds and shut it down!

I will upload a video so you can hear it.

I think the piston rod expanded a little or bearings got loose?

[TownsendsFJR1300]

Your lower bearings (crank and rod) are not needle bearings but solid: https://www.boats.net/catalog/yamaha...nkshaft-piston

I suspect a rod bearing has been cooked / spun... Excess clearance between the crank and rod is likely..

[99yam40]

as I said before,
if you do not monitor the oil pressure with a gauge you have no idea if or how much oil pressure you have.
the alarm will not sound just like it did not when you ran the motor for 10 minuets when you started it without any oil in it.

[Yamaha18]

Your lower bearings (crank and rod) are not needle bearings but solid: https://www.boats.net/catalog/yamaha...nkshaft-piston

I suspect a rod bearing has been cooked / spun... Excess clearance between the crank and rod is likely..

i am going to do 2 things to check: (1) check compression of all 4 cylinders (2) check and make sure I screwed the spark plug tight (no loose spark plugs).

[Yamaha18]

as I said before,
if you do not monitor the oil pressure with a gauge you have no idea if or how much oil pressure you have.
the alarm will not sound just like it did not when you ran the motor for 10 minuets when you started it without any oil in it.

i don't have an oil gauge (do you have the price for the part?), so it will have to wait until I go see Yamaha dealer next week. Yes, I will make sure dealer check oil pump pressure to be sure.

Hopefully when dealer hook up the computer, they will be able to tell me what needs to be replaced.

[ausnoelm]

Computer won't tell you if bearings are shot, computer can't hear knocking either!

[pstephens46]

i am going to do 2 things to check: (1) check compression of all 4 cylinders (2) check and make sure I screwed the spark plug tight (no loose spark plugs).

Spark plugs on these motors are generally torqued to close to 18 lb ft. That’s not really all that tight so be careful.

[Yamaha18]

Computer won't tell you if bearings are shot, computer can't hear knocking either!

Lol, marina who sold me the outboard told me they could tell whats wrong when hooking it up to their computer.

ok so i was expecting computer can read some codes that caused the knocking if there is indeed bearings broken or loosed or piston rod expanding and shrinking.

i am hoping i can open up the powerhead and piston apart myself to fix it to save money if computer is no help.

[Yamaha18]

Spark plugs on these motors are generally torqued to close to 18 lb ft. That’s not really all that tight so be careful.

Wow, good to know. I have a torque wrench and will use it instead of using my easy method to try turning the plug loose by hand.