Broom 33 . Lack of Speed.

[oldgit]

Broom 33 out of the water,the owner is trying to find out as to if the top speed can be improved.
New fuel / air filters and a clean bum.
2 x 180 HP Mercruisers and pair of perfect 4 blade 19 x 23.5 " props.
1500. hours.
Nearly full fuel but no water.
On trip to lift out ,managed to achieve 12/13 knots with the tide, short chop fairly calm. !
Engines rev to 3100 and 3200.
They are supposed to go to 3800.
No obvious smoke.
These boats have reputation for not being quick, even a 1990 Broom 33 on test new from the factory had the wrong pitch according to MBM report.
Claimed top end 22 knots.
Repitch will cost around £300.
We need 600 rpm so 4" (ish) reduction in pitch ?
Is it worth faffing about or just put up with it. ?
All comments welcome especially if you have a 33.
Ps have also posted this on Thames "Pond Forum."

 

[ari]

Clearly something is wrong if they won't make max revs. Even if not bothered about the maximum speed, you'd want to fix that so the engines are not labouring so hard against impossibly high 'gearing'.

With the revs that close it seems unlikely to be an engine fault (unless both engines have precisely the same fault) so if the hull is clean it would seem propellor size/pitch is worth exploring.

 

[simonfraser]

what is the boost pressure from the turbos ?

 

[oldgit]

What is the boost pressure from the turbos ?
Going to try the low hanging fruit first.


With the revs that close it seems unlikely to be an engine fault (unless both engines have precisely the same fault) so if the hull is clean it would seem propellor size/pitch is worth exploring.
Suspect that is the route he will intitally be taking.

 

[simonfraser]

not difficult or expensive to rig up a boost pressure sensor ....
1500 hrs turbos could be tired ?

 

[Jim@sea]

I once bought a brand new Princess 33 where the "claimed" top speed in the printed Brochure was 12 - 14 knots.
Flat out it would only do 10 knots.
Apparently there was a choice of engines which as the boatyard had ordered for stock the one with the smaller engines they did not tell me about the larger choice of engines.

 

[volvopaul]

Broom 33 out of the water,the owner is trying to find out as to if the top speed can be improved.
New fuel / air filters and a clean bum.
2 x 180 HP Mercruisers and pair of perfect 4 blade 19 x 23.5 " props.
1500. hours.
Nearly full fuel but no water.
On trip to lift out ,managed to achieve 12/13 knots with the tide, short chop fairly calm. !
Engines rev to 3100 and 3200.
They are supposed to go to 3800.
No obvious smoke.
These boats have reputation for not being quick, even a 1990 Broom 33 on test new from the factory had the wrong pitch according to MBM report.
Claimed top end 22 knots.
Repitch will cost around £300.
We need 600 rpm so 4" (ish) reduction in pitch ?
Is it worth faffing about or just put up with it. ?
All comments welcome especially if you have a 33.
Ps have also posted this on Thames "Pond Forum."

The first thing I’d do after cleaning the hull props and shafts is to empty the boat of all the heavy cruising gear then test it.

The Volvo 200 hp versions make 20 knots , remember they are propped by the factory as an empty boat with no room for weight addition .
They are a heavy boat for the size , well built but always required more power , if you re pitch you will get the revs up but loose the top speed , 180 hp versions are really river boats these days , you have to remember the age and condition of the engines .

I assume you have done the basics like fuel filters , air filters and checked the exhaust fan for wear on the turbos , all are contributing factors to loss of rpm and speed overall.

Do you have trim tabs fitted ?

 

[oldgit]

Do you have trim tabs fitted ?

Yup ............Bow comes down but precious little else happens
Dinghy has also been removed from davits and taken home.
It apparently had 3 blade props fitted originally, but these were swapped for 4 blades presumably in an expensive attempt to increase speed by previous owner.

 

[Seastoke]

Why would people not address the speed issue when buying

 

[oldgit]

Why would people not address the speed issue when buying

Probably cos they read the brokers brouchure and/or believed the seller.
In this case the boat was bought from the Thames. Not a chance in hell of 20 mins at WOT cruise to watch the temps disappear off the gauge, the alarms deafen all on board followed by the slow crawl of shame back to the marina peering through a cloud of steam.

 

[scottie]

Yup ............Bow comes down but precious little else happens
Dinghy has also been removed from davits and taken home.
It apparently had 3 blade props fitted originally, but these were swapped for 4 blades presumably in an expensive attempt to increase speed by previous owner.

Possibly the other way round bigger props to suit river use with speed restrictions and better low speed results
With oversize props and keep revs down ?

 

[Montemar]

I have a 33 with the 200 hp VP engines and PRM gearboxes which absorb 8 hp leaving me with 190 say from engines with recently reconditioned turbos courtesy of Volvopaul.
My props were originally 20D x 22P x 3 and I got 16 knots at 3850 rpm. I chnaged these to 20D x23P x 4 and cannot achieve max revs so the boat is obviously over propped.
The magazine article we have all seen says the boat with fuel water and people weights 7.5 tons. The calculation done when I bought the 4 blade props used this weight but the weight is wrong.
When the boat was lifted out I asked the crane operator if he could check the weight and was told 10 tons! This must include weight of pulleys, slimgs, steel cable etc but that surely would not weigh more than half a ton. The boat had full fuel tanks, nobody on board ( of course ) and some water.
I used the following to check the prop size:
Free to use Propeller Sizing Calculators
This gave me the 23" pitch solution for 7.5 or so tons but 21" pitch for around 10 tons. This was an explanation for the lack of revs/knots. Furthermore I will be doing well anyway to get 20 knots with the power available - forget 22!
I was informed by someone at Broom that the last 33 to leave the yard with 200hp engines had 20D x26P x 3 props. This is equivalent to 20Dx23Px4 props but probably more efficient.
I will get the pitch on mine reduced to 21" at some cost but if I can get to 3800/3900 revs with full load and a clean hull then I will feel I have got the best out it.
Forget the magaazine article as it bears no relationship to my experience and probably puffed up in Broom's favour. I also spoke recently to an ex Broom man who worked on the 33 and he said they were known to be slow.
He said to use the trim tabs fully as they had a tendency to ride bow high. This has also been my finding.
Oldgits friend's boat is way over propped. Use the Vicprop calculator and put in 10 tons weight and see what comes out. At least his props are 19" diameter so knocking off a chunk of pitch will help. If he has the VP gearboxes then power absorption should be less than 8 hp but he only has 180 hp so not good. It may be worth going to 3 blade props as these are more efficient though give more vibration.
Good luck to your friend. The 33 is a great boat but you need to get up to 16knots to be on the plane without flogging the engines too much.
I hope this helps. I also remember you bought my old 3 bladers so I hope they worked!

 

[volvopaul]

I have a 33 with the 200 hp VP engines and PRM gearboxes which absorb 8 hp leaving me with 190 say from engines with recently reconditioned turbos courtesy of Volvopaul.
My props were originally 20D x 22P x 3 and I got 16 knots at 3850 rpm. I chnaged these to 20D x23P x 4 and cannot achieve max revs so the boat is obviously over propped.
The magazine article we have all seen says the boat with fuel water and people weights 7.5 tons. The calculation done when I bought the 4 blade props used this weight but the weight is wrong.
When the boat was lifted out I asked the crane operator if he could check the weight and was told 10 tons! This must include weight of pulleys, slimgs, steel cable etc but that surely would not weigh more than half a ton. The boat had full fuel tanks, nobody on board ( of course ) and some water.
I used the following to check the prop size:
Free to use Propeller Sizing Calculators
This gave me the 23" pitch solution for 7.5 or so tons but 21" pitch for around 10 tons. This was an explanation for the lack of revs/knots. Furthermore I will be doing well anyway to get 20 knots with the power available - forget 22!
I was informed by someone at Broom that the last 33 to leave the yard with 200hp engines had 20D x26P x 3 props. This is equivalent to 20Dx23Px4 props but probably more efficient.
I will get the pitch on mine reduced to 21" at some cost but if I can get to 3800/3900 revs with full load and a clean hull then I will feel I have got the best out it.
Forget the magaazine article as it bears no relationship to my experience and probably puffed up in Broom's favour. I also spoke recently to an ex Broom man who worked on the 33 and he said they were known to be slow.
He said to use the trim tabs fully as they had a tendency to ride bow high. This has also been my finding.
Oldgits friend's boat is way over propped. Use the Vicprop calculator and put in 10 tons weight and see what comes out. At least his props are 19" diameter so knocking off a chunk of pitch will help. If he has the VP gearboxes then power absorption should be less than 8 hp but he only has 180 hp so not good. It may be worth going to 3 blade props as these are more efficient though give more vibration.
Good luck to your friend. The 33 is a great boat but you need to get up to 16knots to be on the plane without flogging the engines too much.
I hope this helps. I also remember you bought my old 3 bladers so I hope they worked!

I was wondering if you would reply to this post as you are the only Broom 33 customer I know .

Did the new turbos improve the RPM ? I think you got 3000 before the refurb .

 

[Bandit]

Back to basics when was the hull last cleaned so pressure wash it. take all the crap off it and then do runs in each direction up and down the tide say 4 to 6 runs.

What is the weight of the boat lightship?

Without knowing the above two points you are guessing.

I had a Halmatic 34 about 8.5 tonnes full fuel and water 2x 180 VM/BMW/Mercruiser , they went on to make deadmen for moorings about 16 knots.

 

[oldgit]

He said to use the trim tabs fully as they had a tendency to ride bow high. This has also been my finding.
I hope this helps. I also remember you bought my old 3 bladers so I hope they worked!

At WOT the Broom 33 achieved 12.5 knots with the tide, even up top on the command bridge the view ahead disappeared !

"Your" props are coping very well indeed on my P35 , one even survived a hard grounding , which bent shaft and "P" bracket .
Prop was relatively unscathed apart from a wrinkle or two on the tip of one blade.?

 

[Montemar]

I was wondering if you would reply to this post as you are the only Broom 33 customer I know .

Did the new turbos improve the RPM ? I think you got 3000 before the refurb .

Thanks, they did but I then ran into a problem on the starboard engine where there was a water leak in the aftercooler. The drain spigot had been badly soldered at some time and started to leak. It must have reduced the airflow through the matrix probably due to it collecting in the casing. Net result was clouds fo black smoke at anything over 3000 rpm. By the time I had found and sorted it out we were in lockdown so still haven't had chance to properly test the boat.
I wondered if the Rydlime treatment had cleared limescale out that had previously sealed the spigot joint. I do remember seeing an amazing amount of rubbish coming out of the exhausts when the engines were restarted.
I vaguely remember the max revs I got was about 3500 so am now on a mission to find the missing 400!
I note that people talk about 3800 as being max revs but Volvo quote 3900 in their specs. Which is correct...

 

[Montemar]

At WOT the Broom 33 achieved 12.5 knots with the tide, even up top on the command bridge the view ahead disappeared !

"Your" props are coping very well indeed on my P35 , one even survived a hard grounding , which bent shaft and "P" bracket .
Prop was relatively unscathed apart from a wrinkle or two on the tip of one blade.?

I can believe the bow up situation - it is worst just before planing speed.
Glad the props worked well.

 

[volvopaul]

At WOT the Broom 33 achieved 12.5 knots with the tide, even up top on the command bridge the view ahead disappeared !

"Your" props are coping very well indeed on my P35 , one even survived a hard grounding , which bent shaft and "P" bracket .
Prop was relatively unscathed apart from a wrinkle or two on the tip of one blade.?

If thats the boat in question you have too much shaft protruding the P bracket , maximum allowable shaft between the end of the P bracket and Prop hub is 1.5 times the shaft diameter , any more and you will get whip in the shaft and vibration .
Something not right there , looks like someone has added R and D plastic couplings possibly or a spacer to allow rope cutters .

 

[oldgit]

If thats the boat in question you have too much shaft protruding the P bracket , maximum allowable shaft between the end of the P bracket and Prop hub is 1.5 times the shaft diameter , any more and you will get whip in the shaft and vibration .
Something not right there , looks like someone has added R and D plastic couplings possibly or a spacer to allow rope cutters .

Thanks Paul.
Picture is of my P35.
Replacement for bent shaft machined up to the correct and (shorter) length.
The other shaft was also replaced by me due to pitting inside the stern gland and again was cut to correct length.

The boat was previously based in Wales for many years, the shafts/ P brackets were replaced after the skipper heavily grounded the boat .
The boat also had two replacement MS4B fitted early in its life.
There were indentations in shafts suggesting that rope cutters had been fitted at some point.