VP 290 Duo prop Ratios

[Sam Jenkins]

Hi ive potentially got an outdrive on my boat that has the wrong gear ratio (was replaced before i bought the boat). Boats comming out of the water later this week to remove drive and work out ratios correctly. If they are wrong is it in the lower gear housing or the upper gear housing where the reduction happens and if so how easy is it to fit the correct gears cheers

 

[Scott Danforth]

lower gear housing.

all the upper transmissions are the same across the board

easier to swap housings if you are not set up to properly check shims, etc

why do you say its wrong?

what ratio do you have? what motor do you have? what prop set do you have? (b1 thru B8) and what boat do you have?

on a really heavy boat, they may have rigged a different gear case

the small blocks got 1.98:1 the big blocks and diesels got 1.78:1 and the 6-cylinders got 2.15:1

 

[Sam Jenkins]

My boat is a sunseeker Mexico 24 which weighs 2 tonne it has a 5.7 v8 aq271c i had some previous issues with the engine no reving past 2000 rpm loaded up but that is now sorted. And the engine is run as it should be. The props i have fitted are b5s.
Im pulling it out the water and pulling the drive to make sure i dont have any tight bearings and to confirm the ratio a bit more accurately.
When i turned the engine over by hand without the plugs in the ratios didnt seem to match up to whats supposed to be fitted which is 1.95:1 according to the VP prop guide
Cheers

 

[Scott Danforth]

is that 4400# the published weight, or did you actually weigh it?

considering the motor and drive are a 1988, your hull could be water-logged.

in your boat with the stock AQ271C (only paired with a DP290A with 1.95:1) and B5's you should be at about 44-46mph at 4800-5000 RPM.

that is assuming you have the original carb on the boat.

now if you are water-logged, your speed will be down and the boat may struggle to get to WOT RPM as there is more load and more boat in the water.

 

[Sam Jenkins]

When it was lifted in it weighed 2 tonne and that was only 2 months ago. Looking at the build spec it should way around 2 tonne so wouldnt say its logged.
It does have that elderbrock 1409. But would that make it loose 1500 rpm off of the top end cheers

 

[Scott Danforth]

When it was lifted in it weighed 2 tonne and that was only 2 months ago. Looking at the build spec it should way around 2 tonne so wouldnt say its logged.
It does have that elderbrock 1409. But would that make it loose 1500 rpm off of the top end cheers

Covered the carb in your other thread, stock holley carb is a 4150 series at 715 cfm

 

[Sam Jenkins]

lower gear housing.

all the upper transmissions are the same across the board

easier to swap housings if you are not set up to properly check shims, etc

why do you say its wrong?

what ratio do you have? what motor do you have? what prop set do you have? (b1 thru B8) and what boat do you have?

on a really heavy boat, they may have rigged a different gear case

the small blocks got 1.98:1 the big blocks and diesels got 1.78:1 and the 6-cylinders got 2.15:1

It turns out i have a 1.78:1 ratio instead of the 1.95:1
I think im slowly getting to the bottom of my problems

 

[Scott Danforth]

It turns out i have a 1.78:1 ratio instead of the 1.95:1
I think im slowly getting to the bottom of my problems

PM coming

 

[QBhoy]

It turns out i have a 1.78:1 ratio instead of the 1.95:1
I think im slowly getting to the bottom of my problems

Hi Sam.
I’m quite familiar with these boats. I’ve known and been on one a family friend had ages ago. Also familiar with similar U.K. boats around that size and with same engine and drive. Like a few sealines I know.
B5 props would be what’s expected on that set up, all being well. Few wee questions I might ask…
What makes you think it is a 1.78 ratio ?
What was the issue that it wouldn’t go past 2000 rpm ?
Now that it does, what rpm and speed are you seeing out her ?
Are both props stamped as B5 ? Seen it a few times where some have inner and outer props that aren’t matched (by mistake).
Is the 271 the original or only engine that’s been in it ? I’ve known them with diesels in them too, rarely. They may have a different ratio and certainly usually had A series props.
Lovely boats, I’ll also add. Incredible hulls on these things. They should run just a little over 40mph, all being well and trimmed, from memory

 

[Sam Jenkins]

Hi Sam.
I’m quite familiar with these boats. I’ve known and been on one a family friend had ages ago. Also familiar with similar U.K. boats around that size and with same engine and drive. Like a few sealines I know.
B5 props would be what’s expected on that set up, all being well. Few wee questions I might ask…
What makes you think it is a 1.78 ratio ?
What was the issue that it wouldn’t go past 2000 rpm ?
Now that it does, what rpm and speed are you seeing out her ?
Are both props stamped as B5 ? Seen it a few times where some have inner and outer props that aren’t matched (by mistake).
Is the 271 the original or only engine that’s been in it ? I’ve known them with diesels in them too, rarely. They may have a different ratio and certainly usually had A series props.
Lovely boats, I’ll also add. Incredible hulls on these things. They should run just a little over 40mph, all being well and trimmed, from memory

Hi Sorry for the late reply.
Ive removed the drive and rotated the input and im im only getting 1 3/4 turns roughly to 1 of the prop where i should be getting nearly 2 turns to 1 of prop.
This is the orginal engine in the boat but i bought the boat after work had been done to the drive. It had sat in the local boatyard for a couple of years neglected. I bought it as a project and got it back to its former glory.
The issuee with rpm not going over 2000rpm was caused by the original fuel pipe falling apart and sediment in the tank blocking the filters.
That issue is now sorted ive cleaned out tank replaced filters fuel again and fuel lines and ive stripped and cleaned carb.
Its a lovely boat and handles the sea well but just need to get it performing correctly. I will be getting it out the water again at the end of September for the winter to sort this issue out
Cheers