single prop versus duoprop

B

bill56

New Member
Joined
1 Mar 2005
Messages
13
Visit site
Hi everybody, finally got round to my first post! I have a 1983 Sunseeker 28 Offshore residing in the sunny waters of Crete. She was originally twin 200 H.P. V8 petrol,re-engined in 1993 with 130 H.P. Ford FSD 425DI diesels. Luckily, I have a lot of documentary history, all of which shows previous owners spending £££'s on all sorts to do with getting on the plane(engines,fuel pumps, bigger trimtabs,re-siting water tank to bow etc.) Point is, on an underpowered boat( like mine I think), apart from new engines, what can I do to improve things? Toying with ideas like new injectors, overhaul pumps(again), recon turbo's, changing from single to duoprop( currently on 280 legs with 16 X 15 three bladed props) and anything else you lot can think of!!! Please help as now can't even plane (3000 RPM max giving 13 KTS-put this down in some degree to fouled bottom). Any thoughts??
 
Are you sure about the HP output from these engines. I know there are some engines such as the Mermaid that used the FSD 425 to create 130hp, but many marinised FSD 425 DI, will produce less than 100 hp. Again you need to be sure what engines you have as different marinised versions had different max rated RPM's. I have seen some that are rated to 2000, some 3000 and some 4000.

I would give Lancing Marine a call as they specialise in Marinizing ford engines. 01273 410025
 
Boat re-engining was done by Lancing in 1993! It was also featured in MBM so I have all the technical details- in fact Lancing rated them at 140H.P. but I figured 130 was nearer the mark( Mermaid rate theirs at 130).Reason for query in first place was someone mentioned that duoprops would effectively increase output by 15-20% with same setup??
 
In that case def go back to lancing for advise. You need to know what the rated RPM of the engines are. You also need to take the boat out with a clean bottom to see what you are actually getting. Fouling on the hull can make a BIG difference so no point in doing anything without having a clean bum first. Once you have the rated RPM and the RPM's that you are getting, you can adjust the props to give better performance.

If the boat used to reach decent speeds and correct RPM's with the current set up, then you need to look for the cause rather than trying to overcome it with a change of drives or props etc
 
3000rpm sounds like your overpropped. You should be getting more like 3800 to 4000rpm. I take it you have the turbocharged version of these engines. Non turbo's were 75hp approx.

Because you cant achieve the revs, you cannot develop full power from the engines. Try using smaller props to get the revs up first.

It sounds like the boat is a little underpowered, and a previous owner fitted bigger props in order to get more speed. In fact, in doing this, they probably reduced it.
 
It appeared in August 1994 edition, max crankshaft hp-140, max rpm-3800.Take the point that it used to cruise at 20 kts( max speed 25 kts) with THIS setup( last year). When originally re-engined props were 16 X 17(still have them), but spoke to Mike Bellamy at lancing before bringing boat out here and changed to 16 X 15 knowing top speed would suffer but got on plane OK. Have had a very gradual loss of power over last 12 months even though have dived on boat to keep it relatively clean every month or so. Boat now on hard and cleaned ready for new antifoul(maybe try coppercoat or similar as things grow out here VERY quickly). However, I still think unless everthing is perfect, boat struggles(400hp to 260hp is a big drop). Btw max speed @ 400hp was only 32 kts!!??
 
Duo props will definitely help - but you need the right pitch. Find out the weight of your boat, the length overall, the water-line length and the HP available with accurate max RPM.

Then give STEEL DEVELOPMENTS a call and they will be able to advise on correct pitch and style of props. They are really helpful people. Good prices too. Oh, and you can get 2nd hand DP's from COASTAL RIDES if you want. Cheaper than new ones - and you can part ex with your old ones!!
 
Thanks Dave, have spoken to Coastal Rides, they can supply lower leg units(dp) with all the bits for £1250 each leg. Just want to know all my options first, before I take the plunge. Btw just for a laugh, asked for a price on new Iveco(230hp) engines and legs---------£25K!!!!!!!
 
Years ago i had a Sunseeker 31 which is the same hull but stretched with a pair of 260hp VP petrols , it went well 35 knots.

There was a 28 over here that was re engined with a pair of Diesel VP KAD 32p at 170hp each but that engine is discontinued now so if the boat is worth it fit a pair of VP D3 160 or 190hp that should give you a good 30 to 35 knots and diesel economy but only if the boat is worth it after the repower.
 
Clean your (boats)bottom and have good clear out of stuff on boat that does not need to be on board,then check speed and only then spend money!
 
See how she goes after you've re antifouled and put her back in.

On a boat with marginal power for planing (just like my own), every little bit helps. I think changing to duo props or other drives would be a waste of money personally, you will still only have 260hp available regardless of what type of drive it has.

Interestingly, based on a loaded weight of 4 tonnes all up and a 1.5:1 ratio drive, my prop calc programme reckons on 15x13 probs for a maximum 22knots. Not dissimilar from the article.

Simple things first, clean bottom and see what happens. Dont waste money until you find out why it is underperforming in its current set up when compared to the original figures in the article.

If it still doesnt perform as you want after cleaning etc, then you simply need more power. Duo props may inprove efficiency slightly, but its probably wasting time and money by not solving the problem of being underpowered.
 
Hey Bill - is this boat like yours?

50291_1.jpg
 
Thanks everyone for all the helpful comments, don't think it's worth re-engining so have to look at all other possibilities. I seem to remember the drive ratio was not changed when engines were done and I think I was told 1.95: 1 was used on the 200hp petrol setup( but don't quote me on that!). Incidentally Mike Bellamy said he knew the guy who had the engines done and used to see him on the Solent-on the plane (with the16 X17 props)-no problem!! Maybe the engines need a rebuild...........................aaarrgghhh!!!!!!
 
Didn't see your post till just now Dave, but gave me a good laugh to think some other poor sod is in the same boat! Btw mine's a classy blue stripe jobby with go faster(??) stripes...............hey perhaps that's it????
 
Hey Bill, I have a Carver 28 with twin VP Duo props 130hp each and I only manage 23knots or 28knots wot with a really clean bum, have had the injectors cleaned and tried to get more out of it but thats about the best I can get ......
 
Please sir! Please sir!... know lots about Mikes FSDTI's.

They are very susceptable to fouling of the intercoolers and clogging of the air filters.

so, 1. Remove air filters and really wash clean in paraffin.
2. remove intercoolers, its afiddly job at the back of the engines (take the pink air hoses off first its easier) romove end caps from the intercoolers and gently push out the tube stacks. Throughly wash the tubestacks in paraffin before blasting with a jet wash. Rod out the tubes to clean out any crap then reassemble.

3. You may need to clean off the turbo vanes with a paintbrush and more paraffin.

these 3 things will allow the engines to breath more easily and develop the power.
BTW full revs should be 4000 with turbos blowing at 15psi
cruising revs 3500 at 10-12 psi boost. anything less than this and they arent pulling full power.

They are great engines!
 
You must log in or register to reply here.

Share this page

Top