Vintage outboard question - Penta 3.9

[StevenSeagull]

Hi I'm new on here, so I hope this is the right place to ask the question

I have an old AB penta volvo outboard, which I manage to unseize and get working

Not knowing enough about outboards I initally assumed that the air filter was missing, But apparently the smaller ones tend not to have them

However there is something missing that goes in front of the carb:



It is here as shown from this photo I found from another one online. I doubt i will be able to get one the same, but does anyone have any suggestions about what to put there. On this following one it seems to have a nozzle of some sort, which I am surprised at as it would seem to restrict the airflow in.




I am guessing something is at least required to stop bits of junk or splashes of seawater from going in. What would be a good substitute? Or is there a generic thing that i could buy?

Many thanks

 

[neil_s]

I've got one of those motors! Mine is badged as a Crescent 3.9 and originally had a dark grey paint job and a small orange plastic cowling over the power head. The carb intake that you illustrate points upwards on my motor so that it is protected under the cowling. The plastic 'nozzle' that you mention, I can only think is a restrictor to help with the mixture control. Does your motor run well? In its original form, mine could get a Tinker Tramp on to the plane but it has a history a bit like Trigger's broom - one new power head and two new legs. It's not quite so powerful, now. I will get the motor out a bit later and try and measure the bore of the restrictor - you might be able to make one if you can't find a spare.

 

[neil_s]

The bore of the restrictor is 10.5 mm. Here are some photos of my motor.

 

[AntarcticPilot]

A similar gadget on some Seagulls is supposed to keep splashes of water out of the air intake; it's called a "storm cover" However, it does have a wider opening than the gadget you show. In the position shown by neil_s, it would certainly stop water from getting into the carburetor.

 

[Ink]

...also in that position is it not drawing warmer air into the carb when up to temp?

INk

 

[StevenSeagull]

thanks for your replies. I think the one pointing down in my picture has been set wrong then - it seems it shouldn't be pointing 'seaward'! Here is another one i found




Here is one with an air filter (just to confuse matters!)




Also I am reading on both of these (searched on google) - that this an air-cooled engine hmmm, thats news to me

 

[StevenSeagull]

Also if I can find out what the restrictor is called then I can see if I can find an old one somewhere on the net. Its not coming up in searches

 

[neil_s]

There is a lot to be said for these little motors. The powerhead is air-cooled but they are quiet, easy to start and full of beans. They also have a lighting coil and a more efficient, large diameter prop that fits them more as power for a small fishing boat or a small yacht auxilliary. The power head is air-cooled, but the exhaust manifold and leg are cooled by water forced around passages by a scoop behind the prop - no pump! The motor is let down, however, by the light alloy pipe that conducts the cooling water up to the exhaust - this rots out in short order and lets all the water out before it gets to where it's needed. On my motor I have sleeved this in heat-shrink tubing to keep the water in!

 

[StevenSeagull]

Thanks neil , I'll have a look at that scoop/exhaust cooler - I wonder if there is a service manual

Do you have any thoughts on what I could use for the carburettor input thingy?

 

[Ink]

Thanks neil , I'll have a look at that scoop/exhaust cooler - I wonder if there is a service manual

Do you have any thoughts on what I could use for the carburettor input thingy?

How about trying to make one. Suggest try playing with an empty plastic milk bottle to get the shape and rigidity covered and secured with self - amalgating tape.

Ink

 

[neil_s]

Another thought comes to mind - the rubber boot seems to me to be larger than necessary just for a right angle bend. Perhaps the volume is important, too. It might also be there to silence the carb intake. As far as sourcing a spare, I can only suggest e-bay. The discarded engines in marina skips are all considerably younger, these days!

 

[kjell_arne]

Hi @neil_s (or others who might know)

The origianl author here «StevenSeagull» seems to «have flown» somewhere else ;-)
I do have the same Crescent 3.9 hk which I just recently manged to clean up the carburator and adjust the spark plug gap.

Then it started beautifully!
I have search a lot without sucess for «parts list» or «split drawings» to find where the impeller (if there are any?).
I could not see any water comming out from the small hole half way down to the propeller?
Neither did I understand how to dismantle the rod to discover any impeller.

Both you and others have hinted that the motor is air cooled?
Does that mean, there are no impeller to change or fix here?

 

[davidej]

Seem strange to me that this rubber elbow has an inlet that must be about one quarter of the cross section of the carby. Doesn’t that seriously restrict the breathing of the motor ?

 

[neil_s]

Hi @neil_s (or others who might know)

The origianl author here «StevenSeagull» seems to «have flown» somewhere else ;-)
I do have the same Crescent 3.9 hk which I just recently manged to clean up the carburator and adjust the spark plug gap.

Then it started beautifully!
I have search a lot without sucess for «parts list» or «split drawings» to find where the impeller (if there are any?).
I could not see any water comming out from the small hole half way down to the propeller?
Neither did I understand how to dismantle the rod to discover any impeller.

Both you and others have hinted that the motor is air cooled?
Does that mean, there are no impeller to change or fix here?

Welcome, Kjell_arne! - the cylinder is air cooled, but the exhaust manifold and leg are water cooled by means of a scoop behind the prop - so no impeller. There is no piddle hole, either, so failure of the water flow is only detected by burnt fingers!

 

[neil_s]

Seem strange to me that this rubber elbow has an inlet that must be about one quarter of the cross section of the carby. Doesn’t that seriously restrict the breathing of the motor ?

In earlier times, my Crescent 3.9 would plane my Tinker Tramp!

 

[William_H]

My guess would be that the large volume of the tube tapered down to smaller would be for sound deadening of the inlet air. if it points upward it would also give some higher free board if the motor is running but gets submerged in a wave. I would not be concerned to simply useit without the rubber tube. ol'will

 

[Alex_Blackwood]

Hi I'm new on here, so I hope this is the right place to ask the question

I have an old AB penta volvo outboard, which I manage to unseize and get working

Not knowing enough about outboards I initally assumed that the air filter was missing, But apparently the smaller ones tend not to have them

However there is something missing that goes in front of the carb:

View attachment 117017

It is here as shown from this photo I found from another one online. I doubt i will be able to get one the same, but does anyone have any suggestions about what to put there. On this following one it seems to have a nozzle of some sort, which I am surprised at as it would seem to restrict the airflow in.

View attachment 117018


I am guessing something is at least required to stop bits of junk or splashes of seawater from going in. What would be a good substitute? Or is there a generic thing that i could buy?

Many thanks

Have a look on the site below, lots of silicone tubes and bits and bobs. May be of use.
102-76mm Reducing Elbow Silicone Hose | FMR102-76 | Silicon Hoses