F80 Jumped Time?

[MercerRec]

2001 F80 with 700 hours. Ran for a bit, shut it down, then wouldnt restart. Got it off the water, pulled spark plugs, checked comp. 30psi top, zero (or close to it) across the other 3. Plugs look fine. Timing belt missing some chunks out of a few teeth. Anyone have any experience with a similar scenario that can elaborate on the outcome? New here but not to stuff that floats.

[99yam40]

strange one has some compression with the others none.
Could be a non clearance motor and bent some valves when the belt went
may have damaged pistons and rods too

have a look into the plug holes and see if you see marks on top of pistons

[boscoe99]

It is an interference motor. The valves will have collided with the pistons.

[MercerRec]

Believe this is a non-clearance motor. I gave the hairy eyeball downrange and didnt see marks on the pistons, but those plug holes are deep and I dont have a borescope (yet). I just want to make a good decision on repairs before going that route.

[boscoe99]

Pull the head.

[rodbolt17]

why not simply rotate the crank and see if all the timing marks on the flywheel and cam sprockets are still aligned?

that will tell you if it jumped time.

its also why Yamaha recommends belt replacement at 500 hours OR 5 years whichever occurs FIRST.

[MercerRec]

I wasnt clear; it has jumped time. I was wondering if anyone has experience with a similar failure and could ellaborate on costs, etc. Its a new to me non-runner motor. note- tensioner loosened in this photo.

[rodbolt17]

then you have some bent valves.
typically it wont hurt the pistons or camshafts but it will smoke a valve or 10.
fairly simple fix.

and whats funny, the price of the timing belt and the work to access it remains the same.

[MercerRec]

Can someone tell me where the 5 year t/belt replacement interval is documented?

[99yam40]

I have no idea, but it says to inspect and replace as needed every year or 100 hours

[boscoe99]

See the maintenance schedule in this owner's manual.

Owners Manuals | Yamaha Outboards

I recall it being five years or one thousand hours. Five hundred hours would be more conservative still. But in your case the drive belt should have been changed several times by now, at five year intervals.

It is a tough lesson. But as the man says, pay me some money now or pay me a lot more later.

See note three on page 4-9.

An owner's manual and a service manual take precedence over any generic, non-specific document such as the Yamaha MTG by the way.

[MercerRec]

I still dont see any documentation on the 5 year replacement interval mentioned. EDIT FOUND- Footnote 3 page 4-9

In any case, its no lesson for me, as I said its a new to me and I purchased it as non-runner engine. I am going to have it repaired or its parts. My original post was a query for experience with this failure. I came here to ask because you guys run these motors and many of you work on them as well.

At this point, should I install new t-belt and retest compression, and what should the comp # be? Or should I go directly to "pull the head"?

Belt pic attached.

[99yam40]

Rodbolt17 is a Yamaha master tech so if he says it has some bent valves then I would believe him

[MercerRec]

Input taken, will be pulling the head and will report back.

[rodbolt17]

yea its a hard lesson.
its also why when purchashing an older motor simply assume the last owner neglected ALL maint.
they typically do.

I actually have records of customers stuff stretching back to 1989 or so.

I am currently selling a boat for a friends widow that I installed the motor in 1998.
I have records of any and all maint actions from 1998.

its a 25' sou'wester with a 260 hp Volvo with an SX drive if anyone is interested.

but unless otherwise documented ALWAYS do the rubber parts and fuel system maint on ANY used purchase.