Yam F80 Knocking

[Swifty]

My Yamaha Four stroke 80 has developed a bad knocking noise from the engine during the last trip out. Had to get a tow home. Oil level is ok.

Have started stripping the engine down to try and find the cause.
Any experiences or advice as to the likely cause or the potential parts list.

Cheers,
Tim.

[Xk59D]

i'm no expert but the first question is usually does it make noise out of gear. i.e is it motor or gearbox noise.

cheers

[Swifty]

Definately engine. Noise appears to come from the flywheel area.

[Swifty]

Found the cause of the knocking, number 1 Big end failed big time.
Yamaha wanted £2700 + tax for a short block. - ouch.
Took it in to Saunders in Cadnam to see if anything can be done. Turns out it's a Ford crank in a yam case and all may not be lost. - fingers crossed.

Not sure why it failed yet...

[yam man]

Yamaha make the ford focus engine which is what the base engines from 60hp to 80hp from memory also early merc 60 is yam base / ford . Should have ford written on the camshaft if you look closely regards Graham

[yam man]

Originally Posted by yam man

Yamaha make the ford focus engine which is what the base engines from 60hp to 80hp from memory also early merc 60 is yam base / ford . Should have ford written on the camshaft if you look closely regards Graham

Iv never matched the bearings before but I reckon there going to be the same as a focus mk1 1.6 16v big end but are they going to the same material ie White bearing as I'm sure the yam bearings will be because of the engine load at constant high engine speed . Also check your oil pump condition and output being number 1 cylinder big end failed that the furthest away from the pump

[Swifty]

Thanks for the info, will pull the oil pump out and take a look. Are there any known issues with the pump and are there any oil seals I should replace as a matter of course?

Starting a shopping list of bits I will need...

Head gasket
Gasket set (power head, exhaust cover, cam cover)
Timing belt
Oil filter
Oil

[Swifty]

Latest update. Had the crank ground and new shells all round, second hand conrod, honed the bores, new oil seals and head gasket.
All running fine so far.

Have also added an oil pressure gauge for good measure. Have done one hour at low revs, now to do a few hours at mid revs before testing it out at full throttle.

Whole job has cost about £500. Never found exactly what caused the failure, but oil pressure is between 5 & 6 bar now.

[Downhilldai]

You've done well to get that sorted for £500 - good result!

[yam man]

Originally Posted by Downhilldai

You've done well to get that sorted for £500 - good result!

2nd that

[Swifty]

Crank grind £135
Second hand con rod £81
New shells £72
Head gasket (approx) £100
Powerhead gasket (approx) £50
Camshaft seals (approx) £20
Crankshaft seals (approx) £20
Con rod bolts (approx) £30
Oil filter £11
5L Yamaha oil £32

I cannot find the receipt for items (approx) so rough priced.

Lets not price the hours...

Tim.