Replacing power boat engines with something more modern
Discussion
Say, you have an older power boat (early 90's deep v 40ft) with dual volvo penta's (petrol) putting out 330hp each driving through duo props.
Is there much benefit in replacing the engines with newer versions, or another make with a few more horses
Or do you have to replace both motors and drives?
Or just recondition the old ones?
Anyone with any views
Is there much benefit in replacing the engines with newer versions, or another make with a few more horses
Or do you have to replace both motors and drives?
Or just recondition the old ones?
Anyone with any views
Well not much to go on, eg is the existing stuff completely kanckered or...
Volvo Duo-props are imho the dogs wossnames, fairly bullet proof providing you look after them, so I wouldn't be choosing to replace rather than refurb, unless you wanted to be silly and replace with the Axis drive stuff, which is nice and makes close quarter manoeuvres a PoP.
As for the engines, it is sometimes nice to have petrols as you get relatively immune to diesels, and petrols sound so nice. So unless there is a hard and fast reason for changing I'd stick with refurb the lot.
Especially now that red diesel reduced duty has gone and fuel prices are similar.
OK you can make a declaration to HMRC re propulsion and domestic use split and get some reduction that way. But with the high prices that marinas seem to charge for diesel, if you aren't a big volume user (I'm not), it is cheaper to fill up few 10 gallon cans at Sainsbo's*/** when you have got a 5p off voucher from the weekly shop.
Volvo Duo-props are imho the dogs wossnames, fairly bullet proof providing you look after them, so I wouldn't be choosing to replace rather than refurb, unless you wanted to be silly and replace with the Axis drive stuff, which is nice and makes close quarter manoeuvres a PoP.
As for the engines, it is sometimes nice to have petrols as you get relatively immune to diesels, and petrols sound so nice. So unless there is a hard and fast reason for changing I'd stick with refurb the lot.
Especially now that red diesel reduced duty has gone and fuel prices are similar.
OK you can make a declaration to HMRC re propulsion and domestic use split and get some reduction that way. But with the high prices that marinas seem to charge for diesel, if you aren't a big volume user (I'm not), it is cheaper to fill up few 10 gallon cans at Sainsbo's*/** when you have got a 5p off voucher from the weekly shop.
- * Providing you don't get an arsey attendant who objects to you filling up loads of cans.
- ** and you don't mind everybody else thinking, bloddy pikies.
There are a few questions that need answering first.
1, Do you want to re-power like for like. Is yours a V6, V8 small block or big block? New drives and plates will be needed for a change to DPS-A.
2, Do you fancy a Diesel instead? The old Volvo D3 is dead (we've just bought the last 2 available) and the new block D3 will only be available after Jan'10 and there a long waiting list. Once more they are on a DPS-A.
3, Switch to a D4 300hp on a DPH drive; great engine, horrid drive.
4, Search for a pair of KAD300 old engines. Possibly the best engine made by Volvo ever.Normally on a DPG drive.
5, Re-build the old 'uns till they fall apart again.
The choice is yours.
Fish
1, Do you want to re-power like for like. Is yours a V6, V8 small block or big block? New drives and plates will be needed for a change to DPS-A.
2, Do you fancy a Diesel instead? The old Volvo D3 is dead (we've just bought the last 2 available) and the new block D3 will only be available after Jan'10 and there a long waiting list. Once more they are on a DPS-A.
3, Switch to a D4 300hp on a DPH drive; great engine, horrid drive.
4, Search for a pair of KAD300 old engines. Possibly the best engine made by Volvo ever.Normally on a DPG drive.
5, Re-build the old 'uns till they fall apart again.
The choice is yours.
Fish
Fishtigua said:
There are a few questions that need answering first.
1, Do you want to re-power like for like. Is yours a V6, V8 small block or big block? New drives and plates will be needed for a change to DPS-A.
2, Do you fancy a Diesel instead? The old Volvo D3 is dead (we've just bought the last 2 available) and the new block D3 will only be available after Jan'10 and there a long waiting list. Once more they are on a DPS-A.
looking at better performance and want to keep to petrol
3, Switch to a D4 300hp on a DPH drive; great engine, horrid drive.
4, Search for a pair of KAD300 old engines. Possibly the best engine made by Volvo ever.Normally on a DPG drive.
5, Re-build the old 'uns till they fall apart again.
The choice is yours.
Fish
The present engines are twin volvo 740DP and sole reason to change is that I am thinking of better performance, with better fuel consumption, so a better range.1, Do you want to re-power like for like. Is yours a V6, V8 small block or big block? New drives and plates will be needed for a change to DPS-A.
2, Do you fancy a Diesel instead? The old Volvo D3 is dead (we've just bought the last 2 available) and the new block D3 will only be available after Jan'10 and there a long waiting list. Once more they are on a DPS-A.
looking at better performance and want to keep to petrol
3, Switch to a D4 300hp on a DPH drive; great engine, horrid drive.
4, Search for a pair of KAD300 old engines. Possibly the best engine made by Volvo ever.Normally on a DPG drive.
5, Re-build the old 'uns till they fall apart again.
The choice is yours.
Fish
At present the twin volvo 740DP give about 45 knts with a range of 168nm, the tank size is approx 780 lt.
Rebuild what you've got for nothing money. They're only big block chevys 454's in fact and parts are cheap as chips. You can buy a complete long block for about £2k each
There's something not right with your fuel consumption though as they should be burning something like 12 gallons an hour at cruise and 20 gallons an hour at full chat. So it would seem that either they are over fuelling or you are driving everywhere with the throttles planted.
If you want to go down the route of new then a set of 6.3l would cost you close to £15k for the same power. Double or more than that for diesel so any economy savings get eaten straight away.
There's something not right with your fuel consumption though as they should be burning something like 12 gallons an hour at cruise and 20 gallons an hour at full chat. So it would seem that either they are over fuelling or you are driving everywhere with the throttles planted.
If you want to go down the route of new then a set of 6.3l would cost you close to £15k for the same power. Double or more than that for diesel so any economy savings get eaten straight away.
Yes, at full chat about 200 lph (35 gph) but around 25 knts 90 lph.
So if the engines were reconditioned and maybe upgraded any one know how much power early 90's duo props can take?
I would want to increase the top speed of the boat, but without decreasing it's range. I will have about 25k budget,
So if the engines were reconditioned and maybe upgraded any one know how much power early 90's duo props can take?
I would want to increase the top speed of the boat, but without decreasing it's range. I will have about 25k budget,
dictys said:
Yes, at full chat about 200 lph (35 gph) but around 25 knts 90 lph.
So if the engines were reconditioned and maybe upgraded any one know how much power early 90's duo props can take?
I would want to increase the top speed of the boat, but without decreasing it's range. I will have about 25k budget,
It's not so much the top end power as the torque delivery that will tear them apart, hence petrol you should be able to go to about 450 hp but diesel don't expect to run more than 350 hp. So if the engines were reconditioned and maybe upgraded any one know how much power early 90's duo props can take?
I would want to increase the top speed of the boat, but without decreasing it's range. I will have about 25k budget,
Even then you need to start thinking about how you throttle her. If leaving the water you need to be capable of backing the throttles instantly to match the prop speed to re entry or expect the drives to last no time at all.
A set of stainless props will help the efficiency but at the expense of higher drive failure if you're pushing the limits. So there's a balance to be had.
Also if you swap to diesel you need to be thinking about the drive ratios and props. Typical diesels are lower revving than petrol so you need to be able to get a long enough set of props or swap the ratios to get the output into the water.
And don't get into thinking that another 200hp will give you a massive increase in speed. It doesn't work like that with boats which means you need some specific advice for the hull. Get over to Boatmad.com and you'll stand a chance of spending your money wisely.
Just got news today from Volvo that the new D3 is making so much more torque and topend power they have introduced a new range of props.
The new 'I' range takes over from the 'D' range of props. Volvo say they behave like stainless props due to a new casting process but half the price in ally.
Interesting times ahead.
Fish
The new 'I' range takes over from the 'D' range of props. Volvo say they behave like stainless props due to a new casting process but half the price in ally.
Interesting times ahead.
Fish
The answer is don't bother sell it buy something else.
If you spend money ( which will be a whole heap) you will never see it back on a old boat.
Get what you can for it and spend your money on newer complete package. I see it every week people come to and say well i have done this and that so I want this much back out of it.
You have to then tell them sorry its of hardly and value to the sale price.If you want to sell then x is the price if you really want it to go.
Is the boat a Formula by any chance ?.
If you spend money ( which will be a whole heap) you will never see it back on a old boat.
Get what you can for it and spend your money on newer complete package. I see it every week people come to and say well i have done this and that so I want this much back out of it.
You have to then tell them sorry its of hardly and value to the sale price.If you want to sell then x is the price if you really want it to go.
Is the boat a Formula by any chance ?.
Edited by Rum Runner on Sunday 15th November 00:08
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