Bigger outboard restrictions

[totallydave]

Anyone know a good prop shop that might loan me a 17 inch Prop for Honda Bf90?

[mhb100]

I had a pro open 550 with a Honda 90 about the same age and it pulled skiers fine for years. They did change the transom rating for a larger spec I think mid 2000s. You will have a plate on your transom confirming yours. You have a carb model have you ever had them properly cleaned out?. I have a spare stainless prop in the garage, send me your spec and I'll compare as that one was used to tow for years and was taken off to rebush and never was refitted.

[mhb100]

Can you send photo of transom plate, photo of outboard so I can see if it is the carb model as I'm guessing, and one of the numbers stamped on current prop. If you want to swing by Swindon you can try my stainless prop. motor is more than capable to tow.

[totallydave]

Originally Posted by mhb100

Can you send photo of transom plate, photo of outboard so I can see if it is the carb model as I'm guessing, and one of the numbers stamped on current prop. If you want to swing by Swindon you can try my stainless prop. motor is more than capable to tow.

Thanks, I'll get photos and spec over the weekend. It is the Carb version and they were cleaned recently.

[mhb100]

I commute down M4 most days so I guess your about 25 mins from J11. Pm me if you want to meet up to borrow stainless prop.

[jeffstevens763@g]

Originally Posted by totallydave

Prop size is the manufacture standard 19" - I did consider trying a 17" but generally don't swap / remove the prop and didn't really want to loose top speed.

TD

All the prop info I have ever looked at surgest is to pitch down for pulling toys etc it might be a quick fix, I ran my Suzuki 90 with a 14x19 Ali prop 4 up usual kit with very crisp performance 5.85 m rib top speed 45 mph perfect conditions.
Interestingly I have never heard of an outboard stalling so have learnt something.

Cheers

[cgoing]

The Pro 530 has a completely different style hull than the Pro 550 Open. It was also a more heavy duty hull (built in Canada by the Hurricane factory) than the Open style. The ratings on both the 550 and 650 opens have gone up on newer boats along with some other changes.

[beamishken]

If you switch to a stainless prop it's usually recommended to go down a pitch as the better blade design usually means the engine is overproped if you stay the same size.
It may be that the better shape of a stainless prop gives you the improvement you need so if you can borrow a 17 then take the opportunity the improved design might give you better hole shot with little or no loss of top end

The other thing that springs to mind is you say a carb clean / service improved things. It can sometimes take more than one go to get carbs fully cleaned I just did a little 25 yamaha with a similar problem to yours and it took 3 goes in an ultrasonic bath to clean the accelerator pump jet out
I assume yours is multi carb & it could be one or more carbs still has a problem
I've not had much to do with a 90 honda but done a couple of 50's and they were a bugger to get the carbs right
Contrary to what was said earlier it isn't usual for a modern engine to chuck it as you open the throttle but it's not an uncommon fault that can be difficult to rectify and therefore some owners just learn to live with it

[Last Tango]

Originally Posted by beamishken

not an uncommon fault that can be difficult to rectify and therefore some owners just learn to live with it

Straight from the Honda operators manual.....

"Check that the idle port is 150mm or more above the water level"

I think if I choose to ignore this then my problem is misuse and not a fault with the engine.

If it ain't broke don't fix it.

[totallydave]

Originally Posted by Last Tango

Straight from the Honda operators manual.....

"Check that the idle port is 150mm or more above the water level"

Thanks, guess I can check this at rest in the water but can't see me hanging over the back with a tape measure at the same time as giving it full throttle.

[beamishken]

Originally Posted by Last Tango

Straight from the Honda operators manual.....

"Check that the idle port is 150mm or more above the water level"

I think if I choose to ignore this then my problem is misuse and not a fault with the engine.

If it ain't broke don't fix it.

So there probably is something wrong with your set up then? if it's to be 150mm MINIMUM above the water and you need to trim up to get yours clear!
And yours is injection the ops is carbs

[totallydave]

Originally Posted by beamishken

So there probably is something wrong with your set up then? if it's to be 150mm MINIMUM above the water and you need to trim up to get yours clear!
And yours is injection the ops is carbs

To be clear, no one is saying that this is the problem. I'm saying I don't know and would have to try and measure the distance above water.

BTW, mine is not injection, it is multi Carb.

[beamishken]

Originally Posted by totallydave

To be clear, no one is saying that this is the problem. I'm saying I don't know and would have to try and measure the distance above water.

BTW, mine is not injection, it is multi Carb.

It is confusing the issue, your comparing apples and pears
No engine should cut out as you go for full power. Think of it like a car with auto transmission you'd soon complain if it stalled every time you stamped on the gas for a hill start. Yes it's loaded when skiing but it shouldn't chuck it .
You said yourself yours was better after having work which suggests your on the right track. The problem with modern 4 stroke carb engines is the fuel galleries are so small and there are so many little orifices it's easy for 1 or 2 carbs to be fine but the others could have issues which manifest themselves with irritating faults like yours they can be time consuming and difficult to identify
Modern fuel can leave jelly like deposits in the fuel bowls when stood which can block jets easily

A smaler pitch prop may help if your on the upper limit of prop size so trying the stainless prop you've been offered sounds like a good no cost option

[totallydave]

Thanks Beamishken. I guess I also need to find someone who is prepared to spend more time on carb cleaning without charging top dollar.

[Last Tango]

Originally Posted by totallydave

I guess I also need to find someone who is prepared to spend more time on carb cleaning without charging top dollar.

And there's the rub.

You can throw money at this chasing a problem you might not have and I've no doubt the workshop would be only to happy to dismantle your entire engine so long as you're lifting the tab.

Eliminate the simple things first.

My engine only ever stalls if both A: the idle ports are actually under the water (forget the 150mm) and B: I crack full throttle with a skier on the back when it's like this.

The manufacturer's manual tells me in black and white me not to do this and I can, and do run, around a thousand miles a year without it ever stalling if I don't do this, so just maybe there's sound reasoning for their advice.

Moving my trim limit bar to the second hole would be enough to stop this happening and it would still be trimmed well down. So yes, technically there is a flaw with my setup. However the reason I don't set it up on the second hole, is I can hold the boat on the plane down to about 14kn as it's set just now and I find that very useful at times.

The analogy with the automatic car might be a fair one but your torque conversion on "controlled stall rpm (probably around 2000)" will be about 2.4:1 and you'd be complaining bitterly if your prop was slipping like that, basically an auto never loads the engine at idle revs. Also I wouldn't bank on that performance if your main exhaust outlet was under two feet of water and it's only pressure relief also submerged.

Trying another prop is a good shout and if your shopping for one the BF130 has a Mercury/Mariner gearbox. I'd guess the BF90 is the same so there are plenty of props around on the second hand market that'll fit.

[beamishken]

Originally Posted by totallydave

Thanks Beamishken. I guess I also need to find someone who is prepared to spend more time on carb cleaning without charging top dollar.

If your anything like handy yourself then its not a bad idea to do it yourself, you can buy an ultrasonic bath off eBay for about 30 quid you strip the carbs one at a time let them cycle in the bath and reassemble then refit.
It's a job that is well worth knowing how to do as it's a fairly common thing to need doing.

Comparing your problem with last Tango's issue is just confusing things, by his own admission his set up is incorrect and likely the cause of his issue.however a carb engine and a efi engine are totally different animals . Manufacturers know marine engines are on load from the get go and configure their torque curve to accommodate this.
To say you should ignore the issue because he does isn't really helpful as it's obviously pissing you off to the point of thinking of changing the engine

If you do need to take it to a dealer perhaps take it for a run prior and show him the fault and ask him if he thinks A) it is a fault and B)He can fix it within a known budget IE he doesn't just get a blank cheque

[totallydave]

Originally Posted by mhb100

Can you send photo of transom plate, photo of outboard so I can see if it is the carb model as I'm guessing, and one of the numbers stamped on current prop. If you want to swing by Swindon you can try my stainless prop. motor is more than capable to tow.

Photos as requested

[Pikey Dave]

Originally Posted by totallydave

Photos as requested

I've just had a quick scan of the thread & I can't see if anyone has asked what your WOT is, 19" sounds a big big for your setup. What is your WOT with a "normal" load & also when you are towing a skier?

[totallydave]

Originally Posted by Pikey Dave

I've just had a quick scan of the thread & I can't see if anyone has asked what your WOT is, 19" sounds a big big for your setup. What is your WOT with a "normal" load & also when you are towing a skier?

Hi, my WOT is about 5500RPM (assuming the accuracy of the gauge) against a manufacture recommendation of 6000RPM - so I kind of agree, 17 would bring this to 5800-5900. But this was the standard prop for the BF90 at the time.

I haven't tested WOT with a skiier. I don't think it would be massivley difference, the issue is pulling them out, rather than flat-out.

[Pikey Dave]

Fair do's, you're not a million miles away from optimum rpm, so that shouldn't be a factor in your stalling problem. Just a thought.
BTW I've never bought into the "standard" prop thing. I haven't bought an engine yet that came with a "standard" prop. There's no such thing as a "standard" boat[emoji848] when I've bought engines, they are either supplied without a prop & you pay extra for the prop of your choice, or there is an allowance in the price for a bog standard prop to suit the boat.