New Boater Prop Troubles!

[Isthatso]

Evening guys,

New to the boating scene so you’ll have to forgive me for asking the questions. Only silly question is one not asked as they say!

I’ve got an invader 210 sports cabin cruiser

434 A Petrol inboard with a 290 DP drive.

The boat came with one prop and the guy who bought it purchased to flip and never got round to it so he’s not the most helpful with the history.

I purchased a J7 prop as I had access to one for £60 and thought it’s a good place to start to get a baseline.

From my understanding the B series is the preferred prop for this boat and I’m looking to buying one.

I’m currently running WOT @ 3200RPM at a push, the boat isn’t planing at all and the engine sounds like it’s under immense load.

With 4 people on the boat it gets to 2500RPM at WOT and as you can imagine is glued to the water.

Played with it for a few hours adjusting trim, trying to catch my bow wave and it’s just not happening.

My understanding of the J series is that a B series prop will be one numerical number lower for the same pitch i.e J7 = B6

I’m also of the impression that for each drop in number you’ll roughly gain an additional 400rpm

I don’t have thousands to throw at this boat so I’m trying to get this right first time round.

From my ‘maths’ I’ve concluded the following

This engines peak RPM is 4400-4800
I’m currently running at 3200 RPM

I need an additional 1200 RPM to reach 4400RPM at WOT therefore I should drop down to either a J4 or a B3 prop.

I did manage to find an owner from 2005 on Facebook via the history and he *thinks* it was a B5 and it went really well but I’m struggling to see how this is the case given it’s performance with the J7

Just to add, as I’ve not had the boat on a plane, could I be over compensating by dropping down that much pitch, if I drop down to a b5 for example and it has enough power to get itself on a plane will the rpm then roll on to its peak range?

I’m new to the forum scene to do forgive me if I’ve missed any key info out or asked anything stupid.

Thanks guys!

 

[QBhoy]

So just to be clear. Did you just buy one prop for it that’s a j7 ? What was the one that wasn’t missing ? J7 is a fair high pitch. Assuming the ratio is the same as the 290 I had with same engine…I can tell you that I had b5 props on my 23ft cruiser. I wouldn’t go less than that for sure. Assuming your boat is lighter than the one I had. I could pull about 4800 rpm with that set up…and about 35/36 mph from memory.
As far as I knew…a j7 is like a b7 for pitch.

 

[Isthatso]

So just to be clear. Did you just buy one prop for it that’s a j7 ? What was the one that wasn’t missing ? J7 is a fair high pitch. Assuming the ratio is the same as the 290 I had with same engine…I can tell you that I had b5 props on my 23ft cruiser. I wouldn’t go less than that for sure. Assuming your boat is lighter than the one I had. I could pull about 4800 rpm with that set up…and about 35/36 mph from memory.
As far as I knew…a j7 is like a b7 for pitch.

It came with a single front prop and was missing the rear prop from shaft.

I purchased a set of what I was told were b6’s as a baseline to work from.

I’ve been and checked last night they’re J7s

 

[Scott Danforth]

a DP290 will be running two props

you are way way way over proped

for a 4.3, you will be in the B5 range. you dont have enough motor to spin J7's (closer to the A7 than the B7 prop).

 

[Isthatso]

It came with a single front prop and was missing the rear prop from shaft.

I purchased a set of what I was told were b6’s as a baseline to work from.

I’ve been and checked last night they’re J7s

I did see some

a DP290 will be running two props

you are way way way over proped

for a 4.3, you will be in the B5 range. you dont have enough motor to spin J7's (closer to the A7 than the B7 prop).

I thought as much.

I’ll take a drive tomorrow and pick up a set of b5.

Going by the RPM range I’ve provided do you think these will suit? Or would a be better off with a B4

 

[QBhoy]

It came with a single front prop and was missing the rear prop from shaft.

I purchased a set of what I was told were b6’s as a baseline to work from.

I’ve been and checked last night they’re J7s

Sounds like j7’s would be too much for it maybe. But you should defo be able to run b5’s for sure. And maybe even be a little high on rpms with b5’s. Just going from how my heavier boat was. She defo sat around 4800 rpm with them and an Aq205a. Same engine as the 431a. Is the engine definitely healthy ?

 

[Isthatso]

Sounds like j7’s would be too much for it maybe. But you should defo be able to run b5’s for sure. And maybe even be a little high on rpms with b5’s. Just going from how my heavier boat was. She defo sat around 4800 rpm with them and an Aq205a. Same engine as the 431a. Is the engine definitely healthy ?

I believe so.

It was torn down before purchase and apparently the block was machined.

You just don’t know when buying second hand.

Been chatting further with an owner from 2007 and he believes it was supplied with C6 props however he opted for B5s

I think I’ll bite the bullet and order a set.

I’d like stainless but the boats only worth 5/6k so not worth putting £1000 prop set on there if I don’t know they’re correct.

I’ll be slowly refurbing it over my ownership once it’s mechanically sound and maybe then I’ll upgrade.

This prop business is intricate it seems!

The dry weight of this boat is 3000lbs according to a manual I found online

 

[QBhoy]

I believe so.

It was torn down before purchase and apparently the block was machined.

You just don’t know when buying second hand.

Been chatting further with an owner from 2007 and he believes it was supplied with C6 props however he opted for B5s

I think I’ll bite the bullet and order a set.

I’d like stainless but the boats only worth 5/6k so not worth putting £1000 prop set on there if I don’t know they’re correct.

I’ll be slowly refurbing it over my ownership once it’s mechanically sound and maybe then I’ll upgrade.

This prop business is intricate it seems!

The dry weight of this boat is 3000lbs according to a manual I found online

Strange one. If it had c6’s on it. Then j7’s would react not too far off them. Weird that you are down so many rpms, if I read you right initially

 

[Scott Danforth]

J7's have more pitch and an extra blade compared to C6 or B6 requiring more torque to spin at same RPM.

B5's are my recommendation

 

[Isthatso]

Strange one. If it had c6’s on it. Then j7’s would react not too far off them. Weird that you are down so many rpms, if I read you right initially

How do I go about investigating?

I’d like to be certain the motor is running as should be.

Everything sounds okay?

Check compression, check fuel pump pressure, clean carb jets.

Anything else worse checking?

 

[Scott Danforth]

compression will be 150 psi on a good motor

 

[QBhoy]

J7's have more pitch and an extra blade compared to C6 or B6 requiring more torque to spin at same RPM.

B5's are my recommendation

Be somewhere to start…but I know my cruiser had b5’s and pulled 4800 rpm. Boat was 23ft, deep v British heavy built Sealine. Weighed about 2000kgs

 

[Isthatso]

Drove 4 hours yesterday, picked up new B5 prop. Fitted it, boat runs the same if not worse which makes me think it’s engine related and it’s struggling with low end torque or hp output.

I’ve got a list of things to check I’m pulling it out the water this evening. This should be any attained values from the research I’ve done, correct if wrong.

Compression - 140/156 PSI
Fuel Lines - Clear
Plugs, Gaps, Spark
Fuel Pump Pressure - 4/7 PSI
Pull the carb and clean*

Last on list will be timing as I need a strobe…

Anything else anyone can think of that won’t cost me an arm and a leg to check, running out of funds to throw at her now.

It’s a 2bbl carb, can anyone provide me with a link to a service guide and setup for them? Perhaps a manual of sorts?

 

[Scott Danforth]

is the 2-barrel carb a holley 2300? if so, you can clean 90% of it for the price of two gaskets.

if the current gaskets are blue, you could possibly reuse them

what is the spec weight of your boat? what is the actual weight of your boat?

 

[Isthatso]

is the 2-barrel carb a holley 2300? if so, you can clean 90% of it for the price of two gaskets.

if the current gaskets are blue, you could possibly reuse them

what is the spec weight of your boat? what is the actual weight of your boat?

I couldn’t tell you the actual weight of it.

It’s meant to be 3000lbs according to a document I found online

 

[Scott Danforth]

I couldn’t tell you the actual weight of it.

It’s meant to be 3000lbs according to a document I found online

If your boat has any structural issues and you have water soaked foam, you could be carrying around an extra 1000#

 

[Isthatso]

Okay so,

I must have made a major error somewhere in fitting this prop…

First prop goes on.
Torque the prop nut up.
Second Prop on.
Cone Tight.
Locking nut in cone.

So I took the boat out and I’m like I said it ran the same. 2500rpm, grumbled along.

I’ve just removed it and got it home, had a look at the new prop and there is 10mm of material missing from the front prop. It’s been grinding away on the anode and the leg?

I feel like I’m missing a spacer of sorts that slides up the splines before the first prop goes on? Nothing in the diagrams I was sent about it though…

I’ll attach some photos. SOS, this will be an expensive lesson learned I think.

 

[QBhoy]

Drove 4 hours yesterday, picked up new B5 prop. Fitted it, boat runs the same if not worse which makes me think it’s engine related and it’s struggling with low end torque or hp output.

I’ve got a list of things to check I’m pulling it out the water this evening. This should be any attained values from the research I’ve done, correct if wrong.

Compression - 140/156 PSI
Fuel Lines - Clear
Plugs, Gaps, Spark
Fuel Pump Pressure - 4/7 PSI
Pull the carb and clean*

Last on list will be timing as I need a strobe…

Anything else anyone can think of that won’t cost me an arm and a leg to check, running out of funds to throw at her now.

It’s a 2bbl carb, can anyone provide me with a link to a service guide and setup for them? Perhaps a manual of sorts?

Thought it was a little strange. Good to narrow things down though.
Although I’m surprised to read that your engine is a 2 barrel. What exact model is it again ? I thought you said a 431a. Any of them I’ve known were the same as the 205a and had a 4 barrel on them. Common to have auto choke issues too.

 

[Isthatso]

Thought it was a little strange. Good to narrow things down though.
Although I’m surprised to read that your engine is a 2 barrel. What exact model is it again ? I thought you said a 431a. Any of them I’ve known were the same as the 205a and had a 4 barrel on them. Common to have auto choke issues too.

It’s a 434A.

Shall I open a new thread? I have some questions about the compression values I got.

Test was done cold, haven’t tried the old oil down the hatch method to increase psi.

1- 140
2- 107.5
3- 155
4 - 151
5 - 165
6 - 170

 

[72fj40]

Okay so,

I must have made a major error somewhere in fitting this prop…

First prop goes on.
Torque the prop nut up.
Second Prop on.
Cone Tight.
Locking nut in cone.

So I took the boat out and I’m like I said it ran the same. 2500rpm, grumbled along.

I’ve just removed it and got it home, had a look at the new prop and there is 10mm of material missing from the front prop. It’s been grinding away on the anode and the leg?

I feel like I’m missing a spacer of sorts that slides up the splines before the first prop goes on? Nothing in the diagrams I was sent about it though…

I’ll attach some photos. SOS, this will be an expensive lesson learned I think.

I think there should be a spacer b4 you put the frt prop on. You can google v/p 280dp and 290dp dou prop diagram. I think the order is.
Spacer, frt prop, locking ring, lock nut, spacer, back prop, spacer, plastic washer, cone nut, bolt. I think you need to install the prop correctly then see how it runs.

If rpms are still down find out why. Your compression #'s seem all over the place. You might try the test again after the engine is warmed up. Make sure each cylinder hits the same # of times with the throttle open. If the comp #s are accurate wide open rpms will be down.