Broom 33 with 180Hp Mercruiser engines. 1993.

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oldgit

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Anybody hav any clue as to what the original props would have been
The previous owner (Thames based) has fitted a pair of 19" four blade props, the current owner is struggling to get more than 12/14 knots at WOT.
Clean bottom with new antifoul and new oil/fuel/air filters through out. must surely be a bit quicker than that. ?
 
oldgit said:
Cheers, suspect a pair of props for creeping about the Thames has been fitted. New owner states it is reaching max revs.
Not sure what they should be on a D219 engines.
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we are throwing 15"x15" 1.1 gearboxes. if your friend can get max revs with 19" then it should be flying? talk with Paul Williams.
 
omega2 said:
we are throwing 15"x15" 1.1 gearboxes. if your friend can get max revs with 19" then it should be flying? talk with Paul Williams.
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Have spoken to owner he is going to get boat on our drying blocks to find out what is on there, also needs to know the taper before ordering anything.
 
If when the hull and props are fouled it does not reach max revs then I would say the props are correct. If it has PRM hydraulic gearboxes they will absorb 8 bhp per engine.
It could be that the props have been matched to whatever power the engine can produce. The 33 is an old boat and surprisingly heavy for its length.
There is a information about the 33 on the BOC website saying it can do 22 knots. Mine has never got above 19 with TAMB41B, PRM gearboxes, 4 blade 20 dia x 22 pitch.
It could be that 3 blades would be slightly quicker but less smooth.
 
Thanks for that.
Plan now is to get an idea what should be on there first ? Slip the boat and check what is fitted, apparently has 19" props but we not know the pitch.
If its merely a case of too fine pitch, going to take them across to Invicta Marine and get them tweaked .
If prop size to small then its a new pair.

A Classic Tale.
Two Turbo 36s on our moorings both with same engines 255 HP, but one was always faster .
One had 3 and one had 4 blade props.
Cannot remember now which was which but the skipper with the slower boat forked out the best part of 2K for a set of props with the same number of blades as the faster boat.
Course it made boggar all difference, the faster boat was still faster. :)

We have lot of boats on our moorings with the 41 serines 200hp engines, P35/P330/P33 and 30DS etc etc
Ask the skipper what props his boat has and no two boats are same wether in pitch or prop size.
 
oldgit said:
Anybody hav any clue as to what the original props would have been
The previous owner (Thames based) has fitted a pair of 19" four blade props, the current owner is struggling to get more than 12/14 knots at WOT.
Clean bottom with new antifoul and new oil/fuel/air filters through out. must surely be a bit quicker than that. ?
Click to expand...
I have the same issue with my Broom 33 with TMD41B's 150 hp.
The boat is on the hard for the winter and the props are 20x 22 but are worn so having them rebuilt and hoping the to get her up to 17knots after they are refurbished.
 
As you’ll know, the rpm she is getting will certainly tell the tale of what’s going on here.
Out-with fouled hull etc etc... i suspect one of few things. Either it’s not propped well and struggling, poor fuel, not the original engines and underpowered...or these VM engines are suffering some familiar turbo or restricted exhaust issues. The latter can be as simple as the exhaust elbow rotting. Quite common.
 
That help greatly.

22" x 20 seems to be the norm, along with 4 blades.

The owner of the Broom with the Mercruisers is convinced there is not enough room to swing anything over the 19" props that are on there already.
Think he needs to get his tape measure out ?
Anybody know know the taper ?
Always thought the 41B was 200HP. ?
 
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Another thing that comes to mind is "Are the rev counters driven by the alternators, if so are the pulleys on them the same size?. are there boost gauges fitted these give a more accurate read out of engine performance, ours show for instance equal 5lb on the boost but 1800 rpm port and 1900 rpm starboard, and we do have different pulley sizes. Just a thought.
 
omega2 said:
Another thing that comes to mind is "Are the rev counters driven by the alternators, if so are the pulleys on them the same size?. are there boost gauges fitted these give a more accurate read out of engine performance, ours show for instance equal 5lb on the boost but 1800 rpm port and 1900 rpm starboard, and we do have different pulley sizes. Just a thought.
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If anything like mine( VP41B ) they have a sensor picking up the revs directly from something rotating inside timing gear casing.
 
I doubt that 150hp will move the 33 at 17knots.
TMD41B is 150hp and TAMD41B is 200 hp.
Look at Free to use Propeller Sizing Calculators which will give an idea of what is going on.
I once asked Broom what was normally fitted to the 33 and was told 20D x 26P 3 blade on the last one supplied. I do not know which engine but suspect TAMD41 with VP gearboxes.
I suspect my boat is slightly overpropped so may get the pitch reduced by 1" or so. The trouble is that one can go on and on with this.
 
oldgit said:
If anything like mine( VP41B ) they have a sensor picking up the revs directly from something rotating inside timing gear casing.
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41 B is alternator pick up for the Rev counter , it’s the earlier 40 series that has inductive sensor from the timing case gears . Namely the injection pump drive gear .
 
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