Second opinions please - Hylomar vs Gaskets

HughN · 03 May 2014, 15:19

Hi,

In the absence of the pukka gaskets I used Hylomar blue between the castings of the intake manifold / reed as a narrow continuous bead, going round both sides of bolt holes (sufficiently parsimoniously that none should have got into the intake / reeds / cylinders).

Mentioning this to a neighbour this morning he was horrified - as if it was some heinous heretic crime against engineering. This is based on his high-spec bikes.

It is more squishy than paper qaskets would be but I can't see it being an issue; I now have one of those nagging doubts about it giving way whilst out at sea...

RIB-Teccie · 03 May 2014, 16:03

Rolls Royce used Blue Hylomar. I used it on the crankcases of a whole fleet of 55yams without an issue.

Admittedly the tolerances on the crank are arguably better than the reed plate. What you have done is a bit rough, but I can't see it giving way.

If you search the Crowley Marine site in the USA, you will find the correct gaskets and they would be with you in 10 Days, you will have postage options.

Hylomar is a tried and tested product, I couldn't see a terrible failure, just check for any leaks with soap and water prior to going to sea.

uncle al · 03 May 2014, 16:27

I used it for years when I built engines for the army ,I never had a problem with it, not so sure on a OBM though.

beerbelly · 03 May 2014, 16:47

the blue should be ok at least you didn't use the orange stuff countless old triumph motorbikes were killed by that stuff breaking off inside and clogging the oil pickup

Rokraider · 03 May 2014, 18:26

I was taught that Hylomar was normally used in conjuction with a gasket.

beerbelly · 03 May 2014, 22:21

no blue is used on mating surfaces

HughN · 04 May 2014, 07:38

For peace of mind its going to be gaskets...

Thanks,

Hugh

HughN · 04 May 2014, 17:21

Quote:

Originally Posted by HughN

For peace of mind its going to be gaskets...

Thanks,

Hugh

Yep. When it was cranked over it started 'chuffing' fuel and air out between the block and the reed block .

Hylomar off - gaskets going back in (probably with Hylomar Blue / Wellseal, a piece of bailing twine round the powerhead and a couple of 6" nails hammered through the whole lot)

Nos4r2 · 04 May 2014, 21:51

Hylomar blue is bloody awful.
Wellseal is wonderful for non fuel use with gaskets.

Bare gaskets if it's going to be exposed to fuel or fuel/air mixture. Buy new ones. An air leak will kill your motor fast and you won't know it til it seizes.

HughN · 05 May 2014, 10:27

I'm now a bit worried the mating face of the crank-case is the problem.

I had previously tried new gaskets but it still blew fuel/air out from behind the reed-block (blue arrow below) during cranking.

In the absence of some Engineer's Blue and a proper surface table I rubbed the inlet manifold on some 1200 grit wet-and-dry atop a sheet of 6mm safety glass on a 'flat' surface; it seemed flat with no high-spots or dips apparent.

I couldn't do the same with the reed block because of the rubber inserts for the reeds, but using the edge of a steel rule didn't show up any problems (which would have to be significant to show up using that test!).

The bolt nearest that area had a "stripped thread" (wouldn't tighten fully and slipped) but (thanks to your pdf) it now has a bolt of the correct length and the hole has been re-tapped (no room for a helicoil). It now tightens to the specified torque (as do all the others).

A bit of Hylomar on either side of the gasket is probably last chance saloon for what is a twenty yr old engine for which supplies of spares are dwindling - or completely dwindled.

On the plus side, I can now disassemble the inlet stuff blindfold, single-handed and in under three minutes!

HughN · 05 May 2014, 13:22

With a really thin coating of Hylomar Blue on each side of the gaskets it no longer chuffs and runs perfectly - until it runs out of fuel (revs pick up as it leans out then it stops and carb bowl is empty)

* Vent open
* Squeezed/empty primer bulb stays deflated overnight
* A touch of Vaseline round the fuel fittings didn't make any difference
* No damaged hoses
* On the last trip it conked out when the tank got 1/3 full

=> Fuel pump needs overhaul?

matt h · 05 May 2014, 14:37

Wellseal and slightly thicker cotton well places. been using that for old cars for 1907 to 80s and works well

HughN · 05 May 2014, 15:41

Just taken the fuel pump to bits...

There are two checkvalves (20) and a spring (18) and pad (17) in the middle - at least what it should be like...

The pad (17) against the diaphragm was inverted so the spring wasn't seating and the spring was fitted in the recess for one of the check valves. There is a big dent in the diaphragm to prove it!

I'll replace the gaskets / diaphragm before using the boat but at least it runs happily now.