Cruising on single engine 2nd busted

M

Marlin princess

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This is where I am at.
1980 Princess 37 twin engine purchased 6 months before lockdown. Bought with starboard engine running BAD. sounded like turbo, it wasn't. They were replaced new 2010 Iveco 250 hp
The engine is financially unviable to repair. Replacing is not an option either.
The boat is n very good condition otherwise, We had planned coastal cruises Spain & France but are now concentrating inland France, deff not the midi
I have decided to remove drive shaft prop bearings and rudder on starboard. To double the size of the rudder on port side. I will also attach a Bowthruster.
I have a few questions, will reducing the prop size produce more water flow over prop n therefore more control? Has anyone tried or no anyone who has tried this ?
Would appreciate any advice etc.
Cheers, Martin.
 
This is probably too left field and unconventional, but instead of buying a bow thruster, removing prop and shaft etc, would it be feasible to also remove the good 250 hp engine, putting it into storage (or selling it) and fitting a couple of 'small' diesel engines with higher reduction gearboxes (re more torque, so that you can spin the same propellers)?
In view of how you are staying on inland waters they would not have to be very big engines - say 40 - 50 hp each - assuming that you could get suitable gearboxes to suit the propellers.
Or keep the existing propellers in storage as well, and buy a couple of props suitable for 50 hp engines, assuming that they can fit on your larger shafts?
Or (even more left field), remove the two propellers and rudders, and build a bracket on the transom for a pair of high thrust 50 hp O/B motors?
Although realistically, the most sensible thing to do (re keeping some semblance of re-sale value) might be to try to find another 250 hp engine to replace the one that is not viable to repair?
 
Last edited:
Bajansailor said:
This is probably too left field and unconventional, but instead of buying a bow thruster, removing prop and shaft etc, would it be feasible to remove the good 250 hp engine, putting it into storage (or selling it) and fitting a couple of 'small' diesel engines with higher reduction gearboxes (re more torque, so that you can spin the same propellers)?
In view of how you are staying on inland waters they would not have to be very big engines - say 40 - 50 hp each - assuming that you could get suitable gearboxes to suit the propellers.
Or keep the existing propellers in storage as well, and buy a couple of props suitable for 50 hp engines, assuming that they can fit on your larger shafts?
Or (even more left field), remove the two propellers and rudders, and build a bracket on the transom for a pair of high thrust 50 hp O/B motors?
Although realistically, the most sensible thing to do might be to try to find another 250 hp to replace the one that is not viable to repair?
Click to expand...

I once had a Princess mobo that had its two large petrol engines removed and replaced by a pair of 60hp Peugeot diesels. Only pushed the boat at displacement speed, but would have been good for inland waterways.
 
If you finish up stuck with one 250 HP engine on the port side then depending how the boat is set up regarding left and right hand props you might have to switch props and also maybe gearbox to restore some control to deal especially with the combination of paddle wheel effect plus the asymmetrical astern thrust . This will require the right hand prop to be fitted on the remaining port engine if not already there. This may need the gear boxes to be switched. Doing this the paddle wheel effect will help counterbalance the asymmetrical thrust. Mind you the boat will still exhibit a wee bit of leeway :)

Be prepared for an unhappy engine running at such reduced power.
 
A new engine would cost circa £25k But that might be a mismatch for the other engine, it would be normal to replace both engines if that's the case, but that would cost much more than the boat is worth.

Swapping the existing engines for a pair of used, smaller engines, would not cost a fortune, although still be a tidy sum. The effect on the resale value of the boat would almost certainly be great.

Those big mobo engines can usually be rebuilt forever, so i'm also interested to hear what's wrong with it, as it seems from post #1 that it is/was at least running somehow.
 
What the op is proposing would make his boat virtually worthless and
a planing hull won’t be very suitable for trundling about at displacement speeds for prolonged periods inland unfortunately.
 
Flynnbarr said:
What the op is proposing would make his boat virtually worthless and
a planing hull won’t be very suitable for trundling about at displacement speeds for prolonged periods inland unfortunately.
Click to expand...
I agree with the part about the loss of value but there are loads of planing hull boats at my location , and we are a long way from the sea . There isn't a problem doing 5 knots on a river with a planing hull.
 
MartynG said:
I agree with the part about the loss of value but there are loads of planing hull boats at my location , and we are a long way from the sea . There isn't a problem doing 5 knots on a river with a planing hull.
Click to expand...

Try it on one engine !
As someone further up said it’ll not be very controllable
 
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