Spun Prop(Again)

[mibowman]

Greetngs to all and thank you in advance,

Last season I spun the prop on my 1989 yamaha 150 pro v , 3 times. Researching the issue I found that repeated spun props are generally caused by overheated exaust. I am assuming this is correct?? If the cooling system is working correctly, What other reasons are there for over heated exaust? Is the trim tab used to provide more water for cooling? Currently there are 160 degree thermostats installed, are these correct? Do I need to add a low water pick-up unit?

I am completly baffled. Any help would be greatly appriciated.

Best regards,

Brian

 

[rodbolt]

Re: Spun Prop(Again)

why are the wrong T stats installed?
proper stat opening temp is 118 to 126 degrees farienhiet.
get the correct part number back in the heads.
the CORRECT trim tab MUST be used as that is where the extra exaust coouling water comes from.
a little opening at the lead edge of the tab picks up water and sends it to the bearing carrier area for extra cooling of the prop.
if your application runs with the ventilation plate above the water you may have to disscuss it with your prop shop? to either use a solid hub or a different hub materiel as your running outside the engines design.

 

[mibowman]

Re: Spun Prop(Again)

Thank you for your reply. I checked the trim tab and is correct. The thermostats match the part number required.

Could there be an issue in the poppit valve? Where is the location of the valve.

If I was to change the hub, is therea second saftey area if there is a problem?

Thank you so much for your information.

 

[rodbolt]

Re: Spun Prop(Again)

best I recall the stat number should be a 6e5-12411-30 and they are 118-124 stats.
on the hub materiel thats a disscussion with your prop shop.
no you dont have a pressure control valve issue.

 

[mibowman]

Re: Spun Prop(Again)

Greetings again,

If I am correct the poppet valve is also called a water pressure compression valve. Is this the correct part number for this: 6E5-11370-00-00? If not, is there a part number for this?

Just wanted to thank everyone who provides information on this forum. It is a great benifit. Thank you

 

[rodbolt]

Re: Spun Prop(Again)

the purpose of the pressure control valve is simply to control water pressure. if it leaks or sticks open the complaint will be an overheat below about 1100 RPM.
after that it simply dumps excess water back down the ex tube out out the prop.
do you have a water pressure guage? need to if its on a jack plate.

 

[mibowman]

Re: Spun Prop(Again)

Yes there is a water pressure gauge. If I lowerer the jack plate a small amount would that help in getting the proper water?

 

[rodbolt]

Re: Spun Prop(Again)

as long as it can maintain about 11 PSI your jack location is fine.
anything less than 11PSI,above about 2000 RPM, means either a cooling system issue or you ran the jack up to high and are sucking air.
not knowing how high your jacking nor wether your prop blades are cutting air I cant say much.
if the prop blades are cutting air it WILL smoke hubs and wont work correctly unless your using cleaver style props designed to run semi submerged.
there again once you verify its not an engine overheat issue its going to most likly be either its to high on the transom or a prop shop issue.
Yamaha reccomends running the ventilation plate 1inch below to 1 inch above the bottom of the hull.
after that your running outside the designed paremeters and its no longer a Yamaha motor corp issue but a modification issue.

 

[mibowman]

Re: Spun Prop(Again)

Thank you and congrats on your certification.

 

[mibowman]

Re: Spun Prop(Again)

Back again trying to finalalize this issue. Last question: I will only use high octane(above 93) for this engine. I will also use a performance additive for ethanol. With the age of this engine ( 1986 - re-built in 2009) would that create hotter exaust than manufacture specs?

As always, Thank you for you time.

 

[99yam40]

Re: Spun Prop(Again)

The higher the octane the slower it burns, but I have no idea if that would relate to hotter exhaust. In theory it could if the fuel is still burning as it leaves the combustion chamber. The motors are designed to run on 87 according to the manual so that is what I do.