40hp 2 stroke concern

[Sea2aeS]

2000 40hp yamaha 2 stroke PT&tilt. Inline 3 cylinder. The bottom sparkplug has become rusty on the outside of it. 2 sparkplugs above it are clean. swapped the middle plug with the bottom plug and after 2 trips out now, the bottom plug is developing some slight corrosion on it. There is no apparent area where water is entering the engine or exiting anywhere on the block. have noticed a few of the water cover bolts have slight bits of corrosion around the bolts as if they are seeping at the slightest possible amount.

the engine runs fine throughout all rpm ranges, idles fine, doesnt lack power, etc.... havent noticed any performance issues. inside of the plugs are clean, not showing any signs of internal leakage into the cylinders & appear correct in heat range.

-is this a major issue or a small problem thats going to get worse & cost me a ton of money?
im thinking there is the slightest of water leaks around the bottom cylinder with the water cover over the head & the head is fine, but the water cover & gasket may be bad & thats why it runs fine.

please help me with this. Is this a major issue or something that can be fixed or am i worrying myself over nothing? point me in the right direction of appropriate action to take, etc what can happen? what will most likely happen, etc. do i need to get this fixed asap?

[boats.net]

The water may be coming from a back wash when boat comes down off of plain and wave hits cowling or from water spray hitting cowling.

[Sea2aeS]

theres a leak in the water jacket on the #3 bottom cylinder at the base of the sparkplug where it seats on the head/waterjacket. it only seeps at high rpm when running, not at low rpm or idle sitting on the garden hose running on the flusher. im assuming this is due to not enough water pressure at lower rpms so it only shows up at higher rpms?

---is the water jacket bolted to the head with separate bolts or do the bolts hold the water jacket and head to the block as one?
---does the head have to be removed along with the water jacket and is this a simple repair?
---idea on what this kind of work would cost me taking it to a repair shop
$250, $500, $750, $1000?????

[boats.net]

Yes plan on replaceing head and waterjacket gasket, the head bolts have to be removed to get water jacket cover off, here is diagram Yamaha Outboard Parts 2000 40TLRY CYLINDER CRANKCASE Diagram

[Sea2aeS]

Yes plan on replaceing head and waterjacket gasket, the head bolts have to be removed to get water jacket cover off, here is diagram Yamaha Outboard Parts 2000 40TLRY CYLINDER CRANKCASE Diagram

Ok so a few more questions then now that you cleared that part up, im contemplating doing it myself. Im pretty mechanical & this doesnt seem like too bad of a job to tackle, my questions may seem dumb but im no mechanic. I would rather understand & learn than pretend to know it all. Thanks to anybody & everybody for all of your help. Ive got access to torque wrenches & whatnot for proper nut torqing and a clymers shop manual with all the nut torque amounts. im just doing my research to see if this is something I can tackle, or am I better off letting someone with experience in this tackle it instead & not risk doing any damage to my outboard.




-can i run the boat safely like this,& put off fixing this until the fall without worrying about doing any harm to the engine or does it need to be fixed asap before any damage is done?

-Is it pretty much just a matter of removing the water cover, head, & gaskets & replacing with new ones & retorqing


-so I re-use the head, thats obvious since the engine runs fine but do I re-use the water jacket cover or replace with a new one?

-since the head is removed and the gasket is replaced, do I have to run the engine through a break-in period like it were brand new to set the gaskets with 100:1?

-are the head bolts sealed with loc-tite thread lock, or are they threaded with anti-sieze before installation?

-does the engine need the timing re-set after doing this?

-what would cause the gasket on the waterjacket cover to fail like this? & can I run the engine safely for a while & put it off till this fa

[99yam40]

A manual would be a good investment for you if you are going to work on it yourself. Just follow the steps

[Sea2aeS]

I got the Clymers, as stated. It doesnt answer the questions I posted.




-can i run the boat safely like this,& put off fixing this until the fall without worrying about doing any harm to the engine or does it need to be fixed asap before any damage is done?

[boats.net]

If it's spraying water it could cause electrical problems and corrosion problems on engine components.