Princess 25 refurb help

[gary111160]

Having just finished a total refurb of a princess 25, she was launched for sea trial and I must have the wrong prop size.

The engine is a volvo penta 130D petrol with a 280 sp outdrive 1978. Engine should rev to 5100 wot. Out of gear she will rev happily to 5500 but under load no more than 3500 and thats giving me 7 knts at 3000 and nothing from there to 3500. Boat loaded with full fuel, no water, two people no other gear clean bottom.

The prop fitted is a new 15 x 12 which was advised at the time as the one to go for. There was another prop, beyond repair, with the boat when i bought her which is 14 x 11. I don't know if this was the original prop. No history known about the boat other than it appears to have spent most if not all its life on rivers so may have had the original prop changed.

Any one have a Princess 25 and know what size prop they have? or any other suggestions ?

Gary

 

[PCUK]

A very rough guide is that an inch off the pitch increases revs by 200-300. This may give you some idea of the way to go.

 

[david_bagshaw]

the other thought would be the engine is coked up from years of slow running, or have you been there already?

others will know if todays petrol has less output in older engines as well, or will you need an octane enhancer etc.

 

[martynwhiteley]

the other thought would be the engine is coked up from years of slow running, or have you been there already?

others will know if todays petrol has less output in older engines as well, or will you need an octane enhancer etc.

7 K will be about hull speed on the P25 and it will never plane with the current engine.

A prop change will likely get the revs up, but it will prob still max out at about 10K or so. It does seem likely that the engine is well down on power from rated.

 

[gary111160]

the other thought would be the engine is coked up from years of slow running, or have you been there already?

others will know if todays petrol has less output in older engines as well, or will you need an octane enhancer etc.

As far as I can establish the engine is good. Correct compression, no wear in cylinders. Although its 34 years old from the refurb I've carried out its had very little use, no corrosion in engine which is why I suspect only used on fresh water. laid up 7 years prior to my purchase.

New fuel, stainless tank and lines. Did'nt think today's fuel would make much difference but you may be right.

 

[gary111160]

7 K will be about hull speed on the P25 and it will never plane with the current engine.

A prop change will likely get the revs up, but it will prob still max out at about 10K or so. It does seem likely that the engine is well down on power from rated.

Agree with hull speed. Expected to get 12/14 knts. It would have planed originally with this engine and the current weight is about the same as originally specified.

Would engine being down on power not manifest itself by being down on revs in neutral? Anyway I could establish the current rated power?

 

[david_bagshaw]

Would engine being down on power not manifest itself by being down on revs in neutral? without question no. very little power is needed to spin the motor round at any given rpmAnyway I could establish the current rated power?Quite difficult to measure installed, as you need to measure the torque on the output shaft,

Does it sound as if it is being flogged up a hill in too higher gear? or sounds comfy, but wont go faster? if the latter,check the carburettor, as it might be something simple as the auto second stage is not opening. (if fitted)

I havnt worked on volvo petrols, but on a few cars.

have you had the carb apart, what is its design? there are many many things it coul be, blocked jets, jets in the wrong place, second stages that dont open, emulsion tubes blocked etc.

then Ignition system, correct static timing, dwell and the advance working correctly?
7 years laidup, anything with a diaphram has to be suspect. including the lift pump delivering sufficient fuel to burn.


Modern petrols are very different from the late 70s, but others are betterqualified as to how big the impact might be.

 

[gary111160]

Does it sound as if it is being flogged up a hill in too higher gear? or sounds comfy, but wont go faster? if the latter,check the carburettor, as it might be something simple as the auto second stage is not opening. (if fitted)

I havnt worked on volvo petrols, but on a few cars.

have you had the carb apart, what is its design? there are many many things it coul be, blocked jets, jets in the wrong place, second stages that dont open, emulsion tubes blocked etc.

then Ignition system, correct static timing, dwell and the advance working correctly?
7 years laidup, anything with a diaphram has to be suspect. including the lift pump delivering sufficient fuel to burn.


Modern petrols are very different from the late 70s, but others are betterqualified as to how big the impact might be.

Thanks David, lot of food for thought in that! didnt touch the carbs as it starts, idles and no flat spots so I thought they would be ok. There twin Solex 44 PAI.

 

[martynwhiteley]

Most old petrol engines like this will only be delivering a proportion of their original power. Topgear have often tested the old cars they have bought and they are usually well down on power.

My old P25 was a twin. But a mate had one with the same engine and it wouldn't go much above 10 knts. However it would have had more weight and maybe not a clean bum.

My current P286 has twin 131s and was tested new at 24 knts but 13 is the most I've seen so far. I'm hoping that with a bit of tuning and less crew it'll get on the plane but I doub't it will get to more than 16-18 knts.

 

[BarryH]

Thanks David, lot of food for thought in that! didnt touch the carbs as it starts, idles and no flat spots so I thought they would be ok. There twin Solex 44 PAI.

The solex's are a pain when they get older. I had them on a 145 in my old Tremlett. The spindles wear and leak air like a good'un. They need to be balanced. Not just balanced but BALANCED and in sync.
Is your 130 based on the B18 engine. If so check the timing and the dwell angle. They are prone for the centrifugal advance mech to get a bit cruddy and sticky. No vac advance on those, its all mechanical with cetrifugal weights.

Its asking a lot for a 130 to get a fat arsed Princess on the plane, but has been known. I'd also check the drive to see that its not the diesel variant, which has different gearing. It will have a D suffixe on the plate inside.

Failing all else the early duo prop lower gear case fits the 280 as a straight swap. I did it on mine and it was a massive improvement. The fan blades of the singles were never really performance items......!

 

[gary111160]

The solex's are a pain when they get older. I had them on a 145 in my old Tremlett. The spindles wear and leak air like a good'un. They need to be balanced. Not just balanced but BALANCED and in sync.
Is your 130 based on the B18 engine. If so check the timing and the dwell angle. They are prone for the centrifugal advance mech to get a bit cruddy and sticky. No vac advance on those, its all mechanical with cetrifugal weights.

Its asking a lot for a 130 to get a fat arsed Princess on the plane, but has been known. I'd also check the drive to see that its not the diesel variant, which has different gearing. It will have a D suffixe on the plate inside.

Failing all else the early duo prop lower gear case fits the 280 as a straight swap. I did it on mine and it was a massive improvement. The fan blades of the singles were never really performance items......!

Hi Barry.

The engine is a B20, the drive is correct with 2.15 to 1. I did consider a duo prop conversion but thought that it was not possible on my engine! only the 6 cylinders.

Gary

 

[Alpha22]

Don't forget the hull will be considerably heavier now than it was when new. The amount of water that has been soaked up by osmosis could be a factor.

 

[gary111160]

Don't forget the hull will be considerably heavier now than it was when new. The amount of water that has been soaked up by osmosis could be a factor.

Thanks for that, but weight is only a few kg more than new, nothing that would make a great difference.

 

[oldgit]

My P25 with the 175HP V6 on 280T leg would do 17 (ish) knots at a pinch.