IPS Drives

Powersalt

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Being winter and thinking anti fouling etc I just wondered what happens to IPS drives when left for the season.
I mean shaft drives do get weed and barnacles but operate well although maybe a bit inneficient, but how about those lumps of metal sticking down , how does it work??? at the season end
 

Portofino

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Depends on how much torque the base unit engine can deliver.
If it’s the 40/50 ftr IPS with the 5.5 L block then it will imho barely able to knock the skin off a rice pudding never mind and growth / fouling on your props ,
Also with duo props ,in a chicken and egg scenario - the whole point of the smaller block engines ( and tiny torque ) is that the combination of the smaller 2x props ( on two pods ) gives the same thrust to push the hull as a pair of 70 cm bigger props on straight shafts .

Thing is with a straight shaft 50 ftr and 60/70 cm dia props you need huge torque / Hp to spin them to achieve the same performance as the duo pair on the pods .Hence a 12/13 L block kicking out 2500 units of torque as opposed to a D6 churning out what ever ( guess about 1000 torque equivalent units ? )

That 1000 can’t turn a pair of fouled duo props . To get the boat to plane
That 2500 can turn a single ( and bigger ) fouled prop and easily achieve planing speeds .

Sure yo go slower and the load and EGT ,s elivate with fouled props but answering your Q you at least GO .

Interestingly because I can GO with fouled props , I see the boat speed increase with time as the props kinda self clean .The consuption decreases along with the EGT ,s as they effectively self clean to a certain extent .

In the Med the IPS , D6 and KAD outdrives boys after only say 3-4 weeks need a diver or with some legs you can reach from the swim platform.They won,t rev over 24/500 rpm so don,t plane .Alarms kick off with IPS if you push it at 24/500 rpm with the pins pushed all the way fwd .
I have a friend with a D6 IPS set up and the radio msg comes across “ slow down [ insert my name ] my IPS is alarming “
Or they are forced to pootle to a place where they can safely DIY scrub , which is not easy with a IPS boat .

When squeaky clean they don,t alarm off and plane normally .
 
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oldgit

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Being winter and thinking anti fouling etc I just wondered what happens to IPS drives when left for the season.
I mean shaft drives do get weed and barnacles but operate well although maybe a bit inneficient, but how about those lumps of metal sticking down , how does it work??? at the season end

Princess 41 on shafts.. and what turned out to be six months of unusually prolific barnycule growth on props.
8-10 knots max and epic destroyer smoke screen out the back.
No noticeable improvement in speed after journey of 50 miles and 5 hours.
All back to normal in 30 mins after attentions of diver + scraper.
 

Portofino

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Princess 41 on shafts.. and what turned out to be six months of unusually prolific barnycule growth on props.
8-10 knots max and epic destroyer smoke screen out the back.
No noticeable improvement in speed after journey of 50 miles and 5 hours.
All back to normal in 30 mins after attentions of diver + scraper.

Torque - base unit ? An example of what I,am saying .
 

Andyroonot

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Alarms kick off with IPS if you push it at 24/500 rpm with the pins pushed all the way fwd .

I have a friend with a D6 IPS set up and the radio msg comes across “ slow down [ insert my name ] my IPS is alarming “

I’m surprised to hear that alarms are triggered by fouling. How would the engine know it’s spinning fouled props?!? The system will take all parameters and inject enough fuel for the requested throttle position-if the available HP/torque is being wasted by turning fouled props then the RPM will just be lower, and any alarms will be unrelated.

My car doesn’t sound an alarm when going up hill, but the RPM drops unless I change gear...
 

Portofino

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I’m surprised to hear that alarms are triggered by fouling. How would the engine know it’s spinning fouled props?!? The system will take all parameters and inject enough fuel for the requested throttle position-if the available HP/torque is being wasted by turning fouled props then the RPM will just be lower, and any alarms will be unrelated.

My car doesn’t sound an alarm when going up hill, but the RPM drops unless I change gear...

Excess EGT ,s and oil temp rising then eventually after about 10 mins with the throttles pinned Fwds and the thing just hanging there at 2400 rpm in no mans land planing wise or what ever it went into limp mode .

Clearing it and more attempts,just repeats .
Cleaning the props behaved itself and managed to plane .

Boats only have one tall gear .Fouling the props makes. that temporary taller gear and if there’s plenty of spare torque - so what ?
Just accelerates a bit slower but still gets up and planes , no destroyer smoke screen .

Modern stuff like D6 IPS are littered with ECU ,s the sticks are in 100 % open / Fwds , the engines being told dump the lot - go for max injector opening , but it’s cant spin past the 2400 rpm ( due to fouling ) ECUs have a conflab - takes a few minutes to figure there’s a mismatch between the rpm ,throttle position and injector opening times , EGT senor chips in its 2 penny’s worth and the main control brain blows the whistle., calls time .

It can,t produce enough torque to spin the dirty duoprops above said rpm , typically about 2400 .
 
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