Big Twin 40 hp 1969

[benjaminok]

Hello all.

I have an older Big Twin 40 hp 1969 (40902R), which i am trying to rebuild & tune up.
Will change all ingnition parts & impeller, do a carb rebuild and overhaul & reseal gearcase.
As i am waiting for the kits & seals to arrive i have dismantlet the gearcase as i found quite a lot of water in the gearlube. Well the gear itself looks quite nice and now i am just waiting for the seal-kit.

This brings me to my first question:

1) My manual tells me to use a lot of different sealing compound, grease, Adhersive M and so on.
As i have none of them availible right now, what will i need to seal the spagetti seal, upper drive shaft seal & proppeler shaft seal ?

2) Manual says to use a mallet to remove the shifting rod gasket & O-Ring. Also it looks as it is has to go downwards to get out, according to the manual it goes upwards? Have not really god place down there, any good routines to drive this thing out? :% (it is driving me nuts!)

3) The waterpump has no seals at all, i noticed some blue sealing compound below and above the wear-plate?
If there is no seal, is it still necessary to seal the pump and if yes, what to use?

I guess thats all for now, thanks in advance, really appriciate all your help.

Best regards & have a nice weekend!
d

 

[F_R]

Re: Big Twin 40 hp 1969

1. Scotch Grip 847 is the replacement for Adhesive M and Sealer 1000. Part number 776964. It's main advantage is stickiness to hold the spagetti seal in place till you get it put together. And of course to seal it, especially at the ends. You can use plain old Permatex Aviation sealer (the stuff with a brush in the can) in place of OMC Gasket sealant. Any auto parts store has that. Any waterproof marine grease ok.

2. The shift rod bushing is supposed to be removed with a special tool. But you can do it other ways. The tool is a 5/16" rod with the end turned down to 1/4". You can just use a 5/16" rod, but it will buggar up the bushing end a bit, but you can dress that up and re-use it. Another way is to run a 5/16" coarse tap into the bushing about 3 turns and use a threaded rod to pull/push it out. I'm not sure which way it goes without looking. The few threads in the bushing won't hurt it and it can be re-used.

3. Use the permatex sealer below the plate only. Nothing above it. You DO have the seal in the water pump housing don't you? And don't forget to install the o-ring on top of the pump housing. The motor won't run with the hood on if you leave that out. Grease the shaft splines lightly and make sure the o-ring is in that groove too. A dab of grease helps the water tubes slip into the grommets easily.

 

[larky]

Re: Big Twin 40 hp 1969

i recently did a lower unit seal kit in my 59' 35hp and also replace the shift rod bushing. i made the removal tool out of a long punch that i ground down to grip just the bushing. but the most helpfull thing was just a little heat on the case, made it slide right out

 

[benjaminok]

Re: Big Twin 40 hp 1969

Hello guys & thanks for your replies.
Have been busy and awaiting spares which finally after almost 4 weeks are on their way.
Well for the gasket sealent i think i will try to get the real stuff from the local marine tech, as permatex shows to be difficult to get over here for some reason. They use som loctite stuff which i can not figure out which to use or they use permatex 300, well will try the marine shop.

Regarding the waterpump housing, i do have the seal at the top of the housing, but there is NO gasket between wearplate & housing... guess then there is nothing supposed to be down there.

However i am rather confused about the waterpump housing. I have 2 water-tubes coming from the powerhead to the waterpump. The old pumphousing i used before had access to the waterpump from one tube only...the other tube just went into the hole where there is supposed to be a grommet. Say what? (The return line of cooling water just stopped above the waterpump!)
Now the new housing i have has 2 grommets and 2 acesses both leading to the waterpump. According to my drawings there should be a watertube leading away from the waterpump, but this is not the case.
As i see it, both tubes lead to the pump, which i can not really understand. Wheres the meaning in suppling hot cooling water back to the pump??

Hopefully someone is able to understand what i am saying here...
thanks in advance,
BRGDS

 

[F_R]

Re: Big Twin 40 hp 1969

I understand, I think. There is an exploded view of your motor at "http://epc.brp.com/default.aspx?brands=ej&lang=E" Don't use the quotation marks.

Ok, starting in 1968, there are 3 water tubes. One short one leading from the water intake screen aft of the propeller, to the pump housing. This is where the pump gets it's water supply.

From the pump, water goes up one of the two tubes to the powerhead, circulates through the system, then is presented to the thermostat. If the thermostat says it's warm enough, the water is discharged out the exhaust.

But if the thermostat says it is not warm enough, the water is routed back to the pump via the second tube and is recirculated back up to the powerhead, going around and around till it is warm enough. Then the thermostat opens and the hot water goes out the exhaust, and is replaced by cool water from the intake screen.

In actual use, the thermostat cycles open and shut quite often. That's why you may see water discharge heavier at times and barely at all at other times.

Obviously, both water tubes need to have sealing grommets at the pump. There is no gasket under the pump plate, nor between the plate and housing.

 

[benjaminok]

Re: Big Twin 40 hp 1969

Thanks for your answer.
That was actually what i was thinking, the water is recirculated undtil the T-Stat opens.
However part # 61 WATER TUBE, Gearcase is in my lower unit build in the housing as far as i can see. However should do just fine, will mount grommets for both tubes. 8)

Best regards.

 

[benjaminok]

Re: Big Twin 40 hp 1969

Hello guys.

Well finally almost finished, resealed gearcase (which was a pain to get sealed properly), changed the impeller mounted lower unit back etc.
Have rebuiled the carb and changed coils, cond., points and plugs...but here comes my todays problem.
The upper sparkplug gives a nice blue spark, does the 1/4 test and seems perfect.
The lower sparkplug only "once in a while" gives a week spark which only jumps the sparkplug gap and no further. I am a little lost as everything has been changed, points set to 0.22 (new points)...
Also the kill switch wires do confuse me a little as they seem to be shorted. As far as i have understood they are only supposed to be shorted by the kill switch. However they are short without anything connected to them. have tried to measure at the points and they also seem to be shorted?!? I am a little confused about what could be wrong here, and my Clymer manual is of no much help.

Any thoughts?

Thanks and best regards!

 

[F_R]

Re: Big Twin 40 hp 1969

The spark problem might be from a spark plug wire arcing through. This happens often where they are clamped to the armature plate. Or if not that, the wire might be "open", that is no continuity. Check it for that with your ohmeter.

The kill wires go to the breaker points, along with the coil primary wire. There is only about an ohm of resistance through the primary winding of the coil, so it would show up as almost a short to ground on your meter. Making a more careful resistance check at the points or kill wire should show zero resistance with the points closed and about an ohm with the points open. Some ohmmeters are not capable of measuring resistance as low as an ohm, and in those meters you will be fooled into thinking it is a short to ground.

 

[benjaminok]

Re: Big Twin 40 hp 1969

The spark problem might be from a spark plug wire arcing through. This happens often where they are clamped to the armature plate. Or if not that, the wire might be "open", that is no continuity. Check it for that with your ohmeter.

The kill wires go to the breaker points, along with the coil primary wire. There is only about an ohm of resistance through the primary winding of the coil, so it would show up as almost a short to ground on your meter. Making a more careful resistance check at the points or kill wire should show zero resistance with the points closed and about an ohm with the points open. Some ohmmeters are not capable of measuring resistance as low as an ohm, and in those meters you will be fooled into thinking it is a short to ground.

Thanks FR , i think i will try measuring again, this time more carefully.
Yes its probably the plug wires, which is the only thing i did not change....:devil:

 

[Saskatoon2005]

Re: Big Twin 40 hp 1969

I would of changed the spark plug wires as they are not expensive and recieve alot of wear and tear.

 

[benjaminok]

Re: Big Twin 40 hp 1969

Well changed the sparkplug cables today, got spark on both plugs, but wouldnt jump the 1/4. Got tired of messing around with the ingnition and just tried to fire her up and suprise....started at once, idles almost perfect and stayed running.
However i shut her down after about 2 min as i feel there is not comming enough water throug the water outlet.
I am running the engine in a water barrel and the pump is fully submerged. impeller has just been changed but still there is only sqirts of water been shut out of the outlet. The water gets quite hot, however its very cold outside so i am not sure how hot i got.

Now how much water should i suspect to come out of the outlet? A steady big stream of water or might i be OK?
The engine gets quite warm/ hot but i have no temp. sticks or other means of checking the temperature.

Should i keep her running and wait for the T-stat to open?

Your thoughts will be much appriciated.
Thanks for the help so far, i think i am quite close to a good engine d

 

[F_R]

Re: Big Twin 40 hp 1969

The amount of water out the back varies all the time according to whether the 'stat is open or closed at the moment. It does cycle open and closed as speed and load changes.

Having said that, there is just a fine spray discharged when closed, and a heavier spray when open. Never a solid stream.

The motor should never get really hot. But it will get fairly warm. Drizzle a few drops of water on the head to see if it's working OK. It should not boil and fry.

 

[larky]

Re: Big Twin 40 hp 1969

take the thermostat cover off and run the engine, you should get a good spray of water up out of the t-stat housing. After that take the t-stat inside and put it in a pot of hot water on the stove. as the temp comes up you should be able to see it open. if it does not, then replace the thermostat. you may want to replace it regardless. I am by no means an expert, just repeating what i have learned here at iboats. the other more experienced guys may be of greater help.

 

[benjaminok]

Re: Big Twin 40 hp 1969

Thanks for your replies guys, i think i will pull the cover and take a look at that t-stat. i guess it is probably ok, but better safe then sorry.

However at what temperature should the T-stat open and how warm is the discharged water supposed to be?

 

[F_R]

Re: Big Twin 40 hp 1969

It opens at 140-145 degrees.

 

[benjaminok]

Re: Big Twin 40 hp 1969

It opens at 140-145 degrees.

Removed the t-stat cover and found....no T-stat inside.
Well i know the engine will run without, however had a spare in my spare-engine checked that one, opened up fine and reinstalled it.
Tried to run the engine without T.stat cover, a nice thick swell of water running out, seems the pump is working ok.
Still have no IR-termometer, might get one tomorrow to check the temperature, however it is at least not boiling water d

It seems to run okay and idles nice¨. Checked both plugs after i ran it at idle for some minutes and upper plug seemed quite black, some kind of carbon i assume. Lower plug was looking perfect. Tried to remover the plug cables one at the time while running, and both cylinders seem to work as revs decreased with each cable taken off.

What could cause this one plug to get that dark and sooted while the other looks good?
Have no possibility to run it at WOT as it is running in a barrel and shifting it into gear will empty the tank right away d

Thanks in advance, have a nice weekend all you guys!

 

[BoatBuoy]

Re: Big Twin 40 hp 1969

In a previous post in this thread, you said the spark wouldn't jump the 1/4". Ya think that could be the problem with the blackened plug?

 

[benjaminok]

Re: Big Twin 40 hp 1969

In a previous post in this thread, you said the spark wouldn't jump the 1/4". Ya think that could be the problem with the blackened plug?

Well i guess i could be the problem, however both cylinders actually fire, as i can hear the revs ´decrese when taking of the cable for that plug.
Furthermore its the top cylinder getting dark, which actually was the one with the wides jump of spark...?

 

[F_R]

Re: Big Twin 40 hp 1969

Make sure the fuel pump diaphragm isn't leaking. If that's OK, I wouldn't get all excited about that plug. The art of "reading" spark plugs is shady at best on a two stroke that is designed to run continuously anywhere from slow idle to wide open throttle. Dang near impossible to maintain the ideal plug tip temp over such a wide range. Are they both the same heat range plug? Get it out of that barrel and onto a boat in the lake. You might be pleased.

 

[benjaminok]

Re: Big Twin 40 hp 1969

Finally got the boat in the water and testet the B-Twin, started first crank and run quite smooth. d
Runs great at idle and WOT.
Run her for about 3 hours at mixed speed and it seems that the overhaul has been a sucess so far.

However i am still a little confused about the cooling water, it seems that water is only ejected at the rear while running at slow speeds, running at WOT it seems like no cooling water (could this be due to the volume of water circulated through the engine at WOT? Water is only about 46 F at the moment.) Otherwise i am probably just not able to see it because if the pump works at idle it should work at WOT i guess.
Also when slowing down a he** of a lot smoke/steam is comming out of the rear. I guess its hot water/ vapour.
The cylinderhead gets quite hot/warm (still awaiting my IR-meter), but still possible to touch "short time". However the exhaust cover definatly gets hotter then the 170 F which the manual tells me is the maximum.

Any thoughts /sugestions or should i considered it to be ok ?

Anyone with an idea what the fuel comsumption would be at mixed speed or WOT @ hour? I think i already found out it is drinking a LOT or spending halv the fuel to the sea....

Thanks for all your great help so far d