Cylinder head bolts for 4hp Johnson twin?

[prv]

Just bought one of these engines. Nothing wrong with it when purchased (vendor demoed it starting and running fine) but being me I decided to strip, inspect and clean it on arrival. And perhaps inevitably, I've sheared one of the bolts which was corroded in place.

I'm fairly relaxed about extracting it - there's plenty sticking out to grab hold of, and I have some plus-gas on the boat. But obviously I'll now need a replacement (will probably replace all six) and as a thoroughly metric mechanic (I even had to buy a set of imperial spanners specially!) I don't feel confident to measure / identify the bolts.

Anyone know what size I need? And is there anything special about cylinder head bolts, or will anything the right thread and length do? Suggestions of suppliers welcome too.

Cheers,

Pete

 

[TSB240]

I seem to remember that a lot of the thread forms are either UNF or UNC on the Johnson and Evinrude engines. Vic's will be along sooner or later with the best advice!

 

[VicS]

They will be an American thread I am sure as TSB240 suggests...... As you have already discovered you need Imperial AF spanners to fit the bolt heads and nuts on the engine rather than metric ones.

Sorry I do not know what grade they will be and there is no grade marking on the heads

Personally I would buy new bolts as official spare parts from Oakley Marine (aka Outboards Direct) in Brighton ... (Google will find them) although they may be several £ each!

Always quote the HP and model number when ordering spares

The correct torque when refitting is important. ( I have a figure of 60 to 80 inch pounds ... sorry about the units)

You may find some helpful info in the manuals avaialble on http://boatinfo.no/lib/library.html

Generally for help and advice, esp for American makes like Johnson and Evinrude, the iBoats forums at http://forums.iboats.com/forum are very good.
( except that their last software upgrade is an even bigger pile of poo than YBW's last upgrade ! )

Official parts diagrams and lists at http://epc.brp.com/SiteMods/BRP_Public/BRP_Public_Login.aspx?ReturnUrl=/Index.aspx

Or parts suppliers such as http://boats.net/

 

[TQA]

Take a good one along to a nut and bolt [ fixings ] supplier. They will almost certainly have or can get what you need.

As for removing the broken one heat is your friend. Be careful and work it in both directions. If it is seized to the extent it can shear the bolt head it can also shear it at the start of the threads.

 

[prv]

Cheers Vic - Oakley don't see fit to put their stock online, so no business from me today. But the parts diagram revealed a part number of 324334 (putting it here for others' future reference) which I was able to order elsewhere.

I have a set of old PBO cuttings with dismantling instructions; I think they include the bolt torque although I will have to convert to newton-metres for my torque wrench

Pete

 

[VicS]

Cheers Vic - Oakley don't see fit to put their stock online,

True but if you send off an email enquiry from the website someone soon gets back in touch, by phone if you give them your phone number , to check the details etc.

Good old fashioned personal service.

 

[William_H]

The bolt has probably corroded into the head as much as into the thread from the fact that the bolt has snapped off with shaft remaining to grip. Does this mean you have removed the head? If not this will be your biggest challenge to get the other bolts out and the head off. You may snap off more bolts so go very carefully. But I am sure you know that now.
I don't think you were wrong to try to remove the bolts. Indeed I would advocate that you pull all bolts and refit with grease or duralac. What you can't move will have to stay but if yu can't remove the bolt you can't dismantle which may end up being the death of the engine. Bolts on the leg for removing bottom end will probably have been removed many times but do it again. Good luck I have had the 6HP twin for 30 years. Power head is very reliable except the ignition module dropped dead once but most problems have been in water supply/ cooling. good luck olewill

 

[Storyline]

.....
Suggestions of suppliers welcome too.

Cheers,

Pete

If you find it impossible to get a replacement bolt I have got couple of these engines, one in bits and the other needing work after a dunking so would be able to give you a bolt. The problem I have is one of time as I am snowed under at the moment.
Also think I may have a workshop manual which may have specs - will check later
Paul
No info on bolt specs but here are the torques
View attachment 46333
Did the photo on my phone so quality bad - if you want a better one let me know and I will dig the camera out.
I guess the info for the head bolts is this one:
Cylinder head screws - 60 - 84 in lbs (7-9 N-m)
It also says to install the screws dry. Do not use sealant on threads

 

[vyv_cox]

Based on automotive and marine diesel practice I was going to suggest that the bolts should be 'black', i.e. heat treated to the equivalent of a metric 8.8. Having seen those torque figures I would imagine that ordinary mild steel ones would probably be sufficiently strong.

I have bought imperial sized bolts for my BMC engine from an Ebay seller.

 

[prv]

The bolt has probably corroded into the head as much as into the thread from the fact that the bolt has snapped off with shaft remaining to grip. Does this mean you have removed the head?

Yep, the head is off and it's just that one bolt which was stuck. Some of them came out quite easily, others only under protest and accompanied by a lot of white powder. I guess at some point dripping seawater has gone into some of them but not others.

Which reminds me, I need to check through my grandad's old box of imperial taps to see if there's one the right size I can use to clean the thread up. The PBO cuttings I mentioned do specify what to use.

most problems have been in water supply/ cooling.

Indeed, that's why I wanted to open it up, to clean out the water channels. They weren't bad by any means, but still better now the dried salt and crud has been scraped out.

Pete

 

[prv]

It also says to install the screws dry. Do not use sealant on threads

Hmm. I wasn't going to use sealant, but I was thinking of grease (or possibly duralac now it's been suggested) to help the bolts come out next time. However, as it says, those torque figures will be for a dry bolt, and presumably if torqued to the same figure with grease in the threads it will end up under higher tension.

Pete

 

[Storyline]

Anyway Pete, let me know if you are stuck getting one. Also have a problem with tools (as usual) as all my good sockets are on the boat and it sounds like I will also have problems getting one out ! Am happy to be a backup should you need it

 

[prv]

Anyway Pete, let me know if you are stuck getting one.

Thanks - but I'd already ordered them last night (post #5) before you posted this morning

I went sailing today, and collected the tin of plus-gas. I've now annointed the bolt with plenty of it, and filed flats in the sides to grip with a small spanner. Will give it a few days for the fluid to soak in (with top-ups) before I try turning it.

Somebody mentioned heat - if I need to do that, what exactly is the technique? I can heat up the bolt easily enough with the very precise flame of my Iroda iron, but that seems like the wrong way round (I want the surrounding metal to expand, not the bolt). But I don't want to scorch all the paint off the crankcase by trying to heat that instead.

Pete

 

[TSB240]

Thanks - but I'd already ordered them last night (post #5) before you posted this morning

I went sailing today, and collected the tin of plus-gas. I've now annointed the bolt with plenty of it, and filed flats in the sides to grip with a small spanner. Will give it a few days for the fluid to soak in (with top-ups) before I try turning it.

Somebody mentioned heat - if I need to do that, what exactly is the technique? I can heat up the bolt easily enough with the very precise flame of my Iroda iron, but that seems like the wrong way round (I want the surrounding metal to expand, not the bolt). But I don't want to scorch all the paint off the crankcase by trying to heat that instead.

Pete

Heat is not the only trick. In many cases I have found that giving a tap on the end of the thread with a hammer will often have the effect of breaking the thread loose. Often worth giving the head of any bolt into aluminium a bit of a clout (works even bettter before twisting the head off!)

 

[TQA]

Somebody mentioned heat - if I need to do that, what exactly is the technique? I can heat up the bolt easily enough with the very precise flame of my Iroda iron, but that seems like the wrong way round (I want the surrounding metal to expand, not the bolt). But I don't want to scorch all the paint off the crankcase by trying to heat that instead.

Pete

B***er the paint, you need to heat the ali casing. I would smear some white ordinary soap on and heat it till it gets brown. A small butane torch is not really enough. I would use an oven if you have the powerhead off the big burner on the top if not. As to a magic potion I have not time for WD 40 PB Blaster seems to do some good but 50/50 TQF and diesel works well for me.

 

[prv]

As to a magic potion I have not time for WD 40 PB Blaster seems to do some good but 50/50 TQF and diesel works well for me.

I wouldn't expect much from WD40 either. Plus-gas is much better and is what I have applied to this bolt. Surely a purpose-made fluid is going to be better than transmission oil and diesel. Never heard of PB Blaster, but it looks like a US equivalent to plus-gas?

Pete

 

[rogerthebodger]

As I understand it you do have some of the stud exposed if so a can stud extractor is the best too to use

like this

http://www.toolworks.com.au/5041-12mm-cam-stud-extractor-1on2inch-5041-r-repair-kit.html

 

[TQA]

I wouldn't expect much from WD40 either. Plus-gas is much better and is what I have applied to this bolt. Surely a purpose-made fluid is going to be better than transmission oil and diesel. Never heard of PB Blaster, but it looks like a US equivalent to plus-gas?

Pete

I may just be a cynical old fart but feel that many of the magic potions sold in small bottles at high prices are just 'snake oil'. Some work many don't do much. PB Blaster does work in ferrous situations but is not much cop where it is steel in ali as you have. In many years of working on small engines I found the TQF / diesel mix to be efficacious. In your case I would build a small moat using blu tack or Plasticine around the stud add some and leave it to soak down for a day or so. Then apply heat to the ali.

 

[prv]

I may just be a cynical old fart but feel that many of the magic potions sold in small bottles at high prices are just 'snake oil'. Some work many don't do much.

I know what you mean - plus the third common case where it does work but is actually a cheap commodity chemical with a huge markup.

However, plus-gas is well-respected on this side of the Atlantic, and I don't regard it as snake-oil.

I will bear your diesel mix in mind though. I don't have any TQF, but I have some other automatic transmission fluid used in the saildrive. I guess that would be close enough?

Pete

 

[Storyline]

Thanks - but I'd already ordered them last night (post #5) before you posted this morning
.....

Good luck with your extraction - it is a most satisfying feeling when something that has seized frees after you have waited for penetrating oil to do its job - very hard to suppress a scream of delight

If anything else breaks on your new engine give me a shout and I will see if I have it in my engine in bits.