Buy a 5hp Mariner with a blown head gasket?

[kalebsheridan]

I suspect that you know what you really should be doing.

Okay okay I'll buy the gaskets.........

 

[Chris1956]

Do not break the extractors. They are hardened steel, and resist drilling.

 

[airshot]

See if you can find left hand drill bits, they run in reverse and when they bite in, they often unscrew the bolt ! To get started, get a " center drill" of the same dia as the thread dia. The center drill is designed to help stay centered in the hole and make a drill point starting hole in the broken screw on its center. Then use the left hand drill after soaking with penetrating oil.
Good luck....

 

[kalebsheridan]

See if you can find left hand drill bits, they run in reverse and when they bite in, they often unscrew the bolt ! To get started, get a " center drill" of the same dia as the thread dia. The center drill is designed to help stay centered in the hole and make a drill point starting hole in the broken screw on its center. Then use the left hand drill after soaking with penetrating oil.
Good luck....

Yes I ordered some left hand drill bits with paired extractors. I'll have to look into a thread protector though. I'm thinking pilling the power head to get better positioning on the screws on question too.

 

[kalebsheridan]

Has anyone on here pulled the powerhead on one of these motors? I've done it to a 50 hp force but that's it.

 

[Chris1956]

If you have a drill press(or want one), they are real good at drilling out bolts. Pulling the powerhead should be pretty easy, I would think.

 

[kalebsheridan]

If you have a drill press(or want one), they are real good at drilling out bolts. Pulling the powerhead should be pretty easy, I would think.

Man a drill press would be sweet for this. Yeah doesn't look too tricky to pull the powerhead. Looks like the bolts run in from the bottom? Two of the snapped bolts are just too obscured by the lower cowling to leave the powerhead on.

 

[kalebsheridan]

Got the power head off. Broke 2/7 bolts though. They left me enough shank I think I can twist them out. This will make extracting the original bolts much easier.

 

[kalebsheridan]

 

[Chris1956]

You might chase the threads of the bolts that came out, as well as the threads in the casting. Use some Permatex aviation sealant on the bolts upon reassembly.

 

[kalebsheridan]

You might chase the threads of the bolts that came out, as well as the threads in the casting. Use some Permatex aviation sealant on the bolts upon reassembly.

What does chase the threads mean? Aviation sealant? What will that do? Will it stop the bolts from salt welding again?

 

[Chris1956]

"Chase" the threads means cleaning them with a tap or die. Gently run the tap or die over the threads, using light pressure or no pressure. It should restore them to almost new by getting rid of corrosion or old sealer.

The Permatex Aviation sealer is a brush able non hardening sealer. It should make the bolts easy to get out, if you need to remove them in the future.

Look at the bolt heads for their markings. They are likely grade 5 steel. Replace the broken bolts with the same kind of bolts. You may be tempted to use stainless, however, normal stainless bolts are about grade 2, which is not a good replacement for grade 5 steel. Also, SS tends to bond (corrode) in aluminum castings, which is bad.

 

[kalebsheridan]

"Chase" the threads means cleaning them with a tap or die. Gently run the tap or die over the threads, using light pressure or no pressure. It should restore them to almost new by getting rid of corrosion or old sealer.

The Permatex Aviation sealer is a brush able non hardening sealer. It should make the bolts easy to get out, if you need to remove them in the future.

Look at the bolt heads for their markings. They are likely grade 5 steel. Replace the broken bolts with the same kind of bolts. You may be tempted to use stainless, however, normal stainless bolts are about grade 2, which is not a good replacement for grade 5 steel. Also, SS tends to bond (corrode) in aluminum castings, which is bad.

Oh okay makes sense, great info. Especially on the busted bolts. The two head bolts I snapped I was thinking of running to a large hardware store near me to find replacements rather than finding OEM ones. I'll look from proper steel, as well as look for some taps or dies and aviation permanent. I'll put that on all the bolts since I I tend on using this in the salt.

 

[Chris1956]

If that motor is made by Yamaha, the bolts are likely metric. Their marking system is a bit different than SAE bolts, but you should be able to match 'em up.

 

[racerone]

It has been clearly stated that this a YAMAHA built engine !!-----Fasteners are metric.

 

[kalebsheridan]

Yeah they are definitely metric. I'll be sure to use the little thread testers and try to get a good match. Really wish they used beefier bolts for this. Took nothing to snap these.

 

[racerone]

Corrosion and hydrogen " embrittlement " are not well understood.

 

[kalebsheridan]

Well not a ton of luck on the bolt removal yet I've pushed the extractors to the limit on one already, so I'm looking at new options. Id imagine drilling and tapping is next?

 

[Chris1956]

HELICOIL or solid insert is likely next. Drilling and tapping implies lager bolts which may not fit.

 

[kalebsheridan]

Just drilled and tapped one of them. Idk how but I was able to drill out the stud so close the old threads came out like a curley fry. Just tapped it and now the bolt fits. Never tried that before. I'll try to the others and see how it goes.