Zodiac projet 350

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ralf2

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Can any one shed some light on this for me?
My mate bought a zodiac projet 350 today,its old 2001 but very very clean with only 76 hrs,i think its 83 hp,anyways he intends to tow it behind his cruiser on the river ive since been told this is a no no as towing is bad for them?any thoughts as to why,
Also can anyone point me in the direction of obtaining a manual for said boat?
thanks in advance.
 
Owners Manual

In regards the owners manual, i'd try sourcing one from your nearest zodiac dealer (from memory it's A4 size).

Not sure on the towing front, it is a heavy boat for its size and is designed to sit in a garage or a bathing platform. Find it strange to hear of one being used on the river..
 
ralf2 said:
Can any one shed some light on this for me?
My mate bought a zodiac projet 350 today,its old 2001 but very very clean with only 76 hrs,i think its 83 hp,anyways he intends to tow it behind his cruiser on the river ive since been told this is a no no as towing is bad for them?any thoughts as to why,
Also can anyone point me in the direction of obtaining a manual for said boat?
thanks in advance.
Click to expand...

Yes it's the 83hp yam 2 stroke. The only possible reason for not towing is as follows. The engine cooling works by taking water from a pipe tapped off the jet unit near the nozzle. There is no pump; the pressure in the jet forces the cooling water round the engine. If you tow the boat, you will create pressure in the jet and force some water thru the cooling circuit. The engine will not be running of course, and so it is then possible for it to enter the cylinders via an open exhaust valve. Long shot, but it is possible. The faster you tow, the higher the risk

I had this engine in an Avon jet and I can email a pdf of the manual for that boat and the yam engine if you give me an email addy
 
jfm said:
it is then possible for it to enter the cylinders via an open exhaust valve
Click to expand...
Blonde moment J? Exhaust valve on a 2 stroke engine!? :)
That aside, actually there shouldn't be any problem (and on second thought, that applies also to the similar risk which we discussed on the fresh water flushing thread).
In fact, it's a well known fact (though particularly on high performance engines) that with the engine running at idle the risk of water reversion is actually higher than with the engine not running at all.
This is because the engine at idle "breathes" and can actually suck air/water back through the exhaust: exhaust gas flows outside in the inner part of the exhaust tubes, whilst along the internal "wall" of the tubes there is a back flow which can cause water to "climb back" along the tubes, hence causing reversion. It's called exhaust scavenging, I reckon.
And this should apply even more to 2 stroke engines.
So, a properly designed exhaust system should avoid that, by placing the water re-entry point far from the header and giving enough downward angle to the exhaust tube. Which in turn should also eliminate the risk of water reversion when the engine is not running.
That said, obviously I can't guarantee ralf2 that the Zodiac exhaust is actually so carefully designed!
 
MapisM said:
Blonde moment J? Exhaust valve on a 2 stroke engine!? :)
That aside, actually there shouldn't be any problem (and on second thought, that applies also to the similar risk which we discussed on the fresh water flushing thread).
In fact, it's a well known fact (though particularly on high performance engines) that with the engine running at idle the risk of water reversion is actually higher than with the engine not running at all.
This is because the engine at idle "breathes" and can actually suck air/water back through the exhaust: exhaust gas flows outside in the inner part of the exhaust tubes, whilst along the internal "wall" of the tubes there is a back flow which can cause water to "climb back" along the tubes, hence causing reversion. It's called exhaust scavenging, I reckon.
And this should apply even more to 2 stroke engines.
So, a properly designed exhaust system should avoid that, by placing the water re-entry point far from the header and giving enough downward angle to the exhaust tube. Which in turn should also eliminate the risk of water reversion when the engine is not running.
That said, obviously I can't guarantee ralf2 that the Zodiac exhaust is actually so carefully designed!
Click to expand...

No, brunette not blond :-) Of course a 2 stroke angine has an exhaust valve. Sure it's more often called a port than a valve, and it's constructed completely differently from the valve on a 4 stroke, because it's a port in the cylinder wall and the piston's movement opens/closes the port, but it is still a valve in the fundamental sense and there is a still a route to it/through it from the sea

And yes there can be back flow as you describe, but I have no idea of the workings of that Yam 83hp so I don't know how its water flows internally. I was merely putting forward a reason as to why it might be recommended the boat should not be towed which is what OP asked ("any thoughts as to why?"); I wasn't actually pontificating that it should not be towed :-)
 
jfm said:
OP asked ("any thoughts as to why?")
Click to expand...
Well, I must admit that in this respect I don't have any smarter idea... :)
...but I wouldn't be surprised if it would be a very stupid reason like the bow eyebolt not strong enough for towing, considering that the whole thing is pretty heavy, afaik.
 
Thanks for the replies so far,but aside from eyebolt`s,weight of the 350 etc..my main question is with regard to possible engine damage to the tender as a result of towing this rib at say 10 knts
So has anyone towed a projet 350 as a tender?
con m.
 
MapisM said:
Well, I must admit that in this respect I don't have any smarter idea... :)
...but I wouldn't be surprised if it would be a very stupid reason like the bow eyebolt not strong enough for towing, considering that the whole thing is pretty heavy, afaik.
Click to expand...

So you're sticking to your (blond) theory MapisM that a 2 stroke doesn't have valves? :-)
 
ralf2 said:
Thanks for the replies so far,but aside from eyebolt`s,weight of the 350 etc..my main question is with regard to possible engine damage to the tender as a result of towing this rib at say 10 knts
So has anyone towed a projet 350 as a tender?
con m.
Click to expand...

You could just fit an in-line valve in the raw water pick up line (about 15mm bore piping kinda thing, iirc) and shut it for towing. High risk of forgetting to open it when starting motor, so I'd use a solenoid valve that opens when the ignition circuit goes live. Do a proper job of the installation, cos this will not be fail safe if one of your electrical connections fails. Fit a warning light/bleeper on the dash served by the SAME solenoid, if possible
 
jfm said:
So you're sticking to your (blond) theory MapisM that a 2 stroke doesn't have valves? :-)
Click to expand...
'course I do - even if I'm a brunette also myself... and a rather grey one at that! :)
I didn't say that cooling water can't find its way back inside cylinders, just that it isn't through an open valve, in 2 stroke engines.
Otoh, I can't disagree on the principle that a port is still a valve in the fundamental sense... :D
 
ralf2 said:
Thanks for the replies so far,but aside from eyebolt`s,weight of the 350 etc..my main question is with regard to possible engine damage
Click to expand...
Well, you didn't specify that in your OP.
From this viewpoint, I can't see any other reason aside from water reversion.
 
MapisM said:
Good idea. And while ralf2 is at that, he could also fit a T nipple and have a fresh water flushing system as well...!
Click to expand...

There's no need. The Avon 320 jet has as standard a snap on hosepipe connector for freshwater flushing. They stole your idea MapisM :-)
 
MapisM said:
'course I do - even if I'm a brunette also myself... and a rather grey one at that! :)
I didn't say that cooling water can't find its way back inside cylinders, just that it isn't through an open valve, in 2 stroke engines.
Otoh, I can't disagree on the principle that a port is still a valve in the fundamental sense... :D
Click to expand...

I'll pass on this. I really don't have the energy to argue that of course a 2 stroke has valves :-)
 
jfm said:
They stole your idea MapisM :-)
Click to expand...
Blimey! Do you think I could ask him some retroactive royalties for a patent I still haven't registered? :eek:

PS: yeah, let's put the valves issue to rest. It wasn't meant as a serious comment anyway, in the first place - hence the smiley.
I know that you're fully aware of how a 2 stroke engine works. As I'm sure you would have never answered "valves" to a question like "how are the holes in the cylinders of 2 stroke engines called?"... :D
 
MapisM said:
Blimey! Do you think I could ask him some retroactive royalties for a patent I still haven't registered? :eek:

PS: yeah, let's put the valves issue to rest. It wasn't meant as a serious comment anyway, in the first place - hence the smiley.
I know that you're fully aware of how a 2 stroke engine works. As I'm sure you would have never answered "valves" to a question like "how are the holes in the cylinders of 2 stroke engines called?"... :D
Click to expand...

Yup, I'd invoice Yamaha a couple of million euros. You never know...

Scuse me for sounding like someone who insists on having the last word, because I don't so insist, ;), but that isn't the question. The question should be "Is 'valves' an appropriate word to refer to the ports that let exhaust gas out of a 2 stroke engine's cylinders?"
 
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