Yamaha 15hp Enduro 2-Stroke Overheating ?!?!

[Compass790]

It may be just the impeller but the cooling passages as previous posters suggest can be an issue.
Its even worse on the smaller motors, Our 2hp yammer struggles to get rid of the mass of eggs & bay jellys in summer. Almost want to fit a filter & flow alarm if it wasnt a major.

My advice if you pull apart is use loctite 242 or equivalent on every bolt as they seize in the alloy as it corrodes. It seems counter-inuititive to use loctite but I find it stops the corrosion. You could use anti-sieze but then you run the risk of a bolt coming loose.
Only thing ( frm memory ) I use anti-seize on is exhaust bolts

[Kiwi Dave]

Hi - a fairly bullet proof motor.

Back when I had a 15hp Yamaha 2 stroke it was common for water not to flow out the ?indicator jet at the back of the motor due to salt/corrosion blocking the junction of the rubber hose to the plastic jet inserted into the case below the power head. Just remove the rubber hose from it - if there is flow then clean the jet.

Most recently had blades missing from the impellor and had to do a major disassembly to find them in the water ways. You are lucky that the impellor is intact (but old)

[GoneDiving]

Originally Posted by Compass790

It seems counter-inuititive to use loctite but I find it stops the corrosion. You could use anti-sieze but then you run the risk of a bolt coming loose.
Only thing ( frm memory ) I use anti-seize on is exhaust bolts

My local Yamaha Service Center specifically advised against using antiseize saying that introducing a third metal makes dissimilar metal corrosion even worse. I just clean the threads, apply a very light smear of grease, then torque to specs. Works for me.

[Scubaseas]

Originally Posted by Compass790

It may be just the impeller but the cooling passages as previous posters suggest can be an issue.
Its even worse on the smaller motors, Our 2hp yammer struggles to get rid of the mass of eggs & bay jellys in summer. Almost want to fit a filter & flow alarm if it wasnt a major.

My advice if you pull apart is use loctite 242 or equivalent on every bolt as they seize in the alloy as it corrodes. It seems counter-inuititive to use loctite but I find it stops the corrosion. You could use anti-sieze but then you run the risk of a bolt coming loose.
Only thing ( frm memory ) I use anti-seize on is exhaust bolts

This. Put blue loctite 242 on everything , especially stainless hardware as it will prevent galling. This goes for rigging stuff also, not just engines.

[Compass790]

Originally Posted by GoneDiving

My local Yamaha Service Center specifically advised against using antiseize saying that introducing a third metal makes dissimilar metal corrosion even worse. I just clean the threads, apply a very light smear of grease, then torque to specs. Works for me.

Fair point,
Could be true if he's talking copper anti-sieze. I should have said I was thinking of the diesel exhaust not the outboard exhaust as well.
Pretty much only use 242 on the outboard
However if you use nickel anti-seize as I do it is no different than an ss bolt which is a fair % nickel.

It's hard to do a short post & cover everything .

[sailjumanji]

FIRST thing to do. Get a piece of siezing wire and shove it in the motor telltale ("pee hole") and work it around a bit. Its pretty common for them to salt over, or have an insect clog.

[Tspringer]

Originally Posted by PhilC

When you have it all back together with a new impellor you should have a telltale jetting water and if it has one (and as soon as up to temp) water flowing out the larger hole in the back of the leg (mixed with exhaust gas). If you have both of these great! If you don't then you need to start trying to isolate where the blockage is. Start by cleaning out with a piece of wire any accessible parts of the telltale. Then remove the thermostat housing, test thermostat and clean out all you can reach from there. If that dosent work then feel around the head and exhaust jacket area with your hands (or using digital thermometer) after a short run. Raw water cooled engines need to run cool <70deg C to avoid forming salt crystals - if you can hold your hand on any part of the powerhead for few seconds before it becomes uncomfortable that's around 70deg. This is important because you need to figure out which bolts to undo to access a site of a potential blockage (the head or the exhaust jacket) if it's a 90's motor you are likely to break a fair percentage of the bolts undoing them so the less you undo the better.

Thermal dynamic evaluation on the fly is my thing. I got a CAT S61 phone with a FLIR camera. Works great for looking at things that get hot. Heat exchangers and cylinder heads and electric pumps always make for fun viewing. Blocked heat exchangers become obvious. Same for leaky water pumps. Good toy to geek out on mechanical stuff.

[wind rose ll]

Has anyone mentioned where the water intake is on this model? L have one and want to flush it but can not locate which holes are intake? I don't know if "ear Muffs" can be used to flush?

[wind rose ll]

Just found this..Yamaha OEM Part Abb-flush-jd-00 Jet Drive Flush...it appears as though this would screw into the intake opening and allow direct connection to a water source...anyone know the thread size? l could easily make one.

[wind rose ll]

how do you insert a image?

[PhilC]

The pickup will be under the anti ventilation plate (just above the propellor) run it in a bucket rather than earmuffs.

[wind rose ll]

I had noticed that intake but after finding the flushing tool l had posted figured the small hole that it screws into could be fed water using the muffs.