M40C outboard head bolts grade.

[titaniumneck]

Replacing blown headgasket on my Tohatsu M40C, ordered headgasket from this site, but didn't notice until after ordering gasket that my old head bolts were rusted and pitted. The bolts only marking is a lower case b on them. I cannot find anything about these bolts as far as grade. I am going to go to Napa and get some head bolts from there, but I need to find out what grade of bolt I need. The service manual identifys them only as H845-10. Does anyone know how to find out what grade bolt I am looking for, or anything. Any input will be greatly appreciated. I don't want to have to make a separate order for them and have to pay for the shipping again.

 

[pvanv]

You can get OEM bolts from Tohatsu. Probably grade 5 or better.

 

[titaniumneck]

Ok thanks.

 

[Sea Rider]

OEM Tohatsu head bolts are under $ 2.00 each + shipping. Before you install new head gasket along new bolts, make sure you don't have already a warped cylinder head due to continous overheats. Lie head on top of a glass, mirror, shim a paper, thin metal sanding sheet under middle head, check if passes through easily, if it does, will need to send head to a machine shop to flatten it again or gasket will not seat, seal conveniently against both mating surfaces. Could have compression loss, water entering combustion chamber and OB not working properly.

Check thermostat condition, if severely burnt, heated up, install a new one along thermo gasket.

Happy Boating

 

[titaniumneck]

That's another thing, it doesn't have a thermostat in it. Somebody told me in South Louisiana you don't really need a thermostat since it doesn't get that cold. Is this true or false.

 

[Sea Rider]

A thermo is there for some reason, the only issue I see is that OB will take longer to reach optimum heat operating temp range specially on cold starts and re starts. On 2 strokes could foul plugs prematurely when warming up at neutral & idle. Is water temp same, near same as in Fla ? Will need to throw extra $ 30.00 for thermo and gasket if wanting to count with OB in good working order as factory delivered.

Depending on water temp and throttle, a thermo could open more or less, it's not like turning a light on-off in which you have only 2 working positions.

Happy Boating