Some help pitching a prop please.

[GILow]

Originally Posted by Ann T. Cate

Matt,

That big old wheel you're towing around really will slow you down. Have you considered a 3 blade folder? Jim is quite pleased with our Flex-O-Fold. Ordered it out of Massachusetts in the States.

Ann

Hi Ann,

Yes, it is a bit of a handbrake, but I am a KISS principle kind of guy, and folding props give me the heeby jeebies. I know they are a lot more reliable than they used to be, but my early experiences of them on dad's boats turned me off them. I may be tempted later on, depending on how many miles we do on Manera, if we end up doing the sort of mileage you and Jim manage I think I would be a lot more tempted.

Mind you, I have to figure out the right prop size first, and that is best done with the cheaper fixed blade sort I think.

Matt

[JPA Cate]

Originally Posted by GILow

Hi Ann,

Yes, it is a bit of a handbrake, but I am a KISS principle kind of guy, and folding props give me the heeby jeebies. I know they are a lot more reliable than they used to be, but my early experiences of them on dad's boats turned me off them. I may be tempted later on, depending on how many miles we do on Manera, if we end up doing the sort of mileage you and Jim manage I think I would be a lot more tempted.

Mind you, I have to figure out the right prop size first, and that is best done with the cheaper fixed blade sort I think.

Matt

Fair enough,
We've only had this one for 10 yrs., and all well with it so far. At one point on a previous boat, we had a 2 blade folder: that one did not work very well in reverse. For reversing, the 3 blade FOF is better. I was just thinking of saving the cost of an "extra" prop. Ah, well, now you can have two "spares", or maybe sell one of them, or get the prop guys to take the old one in trade??????

Good luck with it.

[Jim Cate]

Originally Posted by GILow

Hi Ann,

Yes, it is a bit of a handbrake, but I am a KISS principle kind of guy, and folding props give me the heeby jeebies. I know they are a lot more reliable than they used to be, but my early experiences of them on dad's boats turned me off them. I may be tempted later on, depending on how many miles we do on Manera, if we end up doing the sort of mileage you and Jim manage I think I would be a lot more tempted.

Mind you, I have to figure out the right prop size first, and that is best done with the cheaper fixed blade sort I think.

Matt

G'Day Matt,

Yep, experimenting with a less expensive prop is a good idea IMO. Also, if it turns out that you really need a very small diameter prop with your gearing, a folder isn't gonna be real good. Has to do with the fixed size of the hub, and thus rather short blades.

I know that this isn't what you want to do, but you might look into the availability of your tranny in a higher reduction ration. It is conceivable (barely) that an exchange might be possible, and for less money than a replacement prop and a slipping to change it.

It just seems to me that a bigger, slower turning prop is what is called for in boats like yours. Sure hope that you can resolve the problem, mate.

Cheers,

Jim

[GILow]

Originally Posted by Jim Cate

G'Day Matt,

Yep, experimenting with a less expensive prop is a good idea IMO. Also, if it turns out that you really need a very small diameter prop with your gearing, a folder isn't gonna be real good. Has to do with the fixed size of the hub, and thus rather short blades.

I know that this isn't what you want to do, but you might look into the availability of your tranny in a higher reduction ration. It is conceivable (barely) that an exchange might be possible, and for less money than a replacement prop and a slipping to change it.

It just seems to me that a bigger, slower turning prop is what is called for in boats like yours. Sure hope that you can resolve the problem, mate.

Cheers,

Jim

Jim,

I did actually start looking at that very idea, you are right, a big slower revving prop would suit the boat well, goodness knows I need all the grip I can get when bring the boat into her pen after sailing too.

I found plenty of 1.5:1 transmissions, but no other ratios. I will broaden my search a bit today. Given I have to attend to the little spring whatsits in the bell housing, removing and replacing the transmission is on the cards anyway.

As a matter of interest, a 2:1 transmission would pretty well match the prop I currently have perfectly... another reason to pursue your idea....

Back on the phone it is...

Matt

[GILow]

Update: Well, I found a reco 2:1 71c box, Counter Rotating, so I'd still have to replace the prop, and they are asking $4K. Yeah, right, THAT is not going to happen.

I'll keep hunting, but honestly, welcome to Oz. Boat owners should hand over their money at the border.

I think I will move to New Zealand.

[Opie91]

Matt,

Is this the original engine to the boat? I looked around the internet and found a few with the following engine set up:
"Ford Bowman 3404 4 Cylinder Diesel with Wet Exhaust. Velvet Drive Gearbox 2.4:1 Reduction"

Maybe they changed the engine and did not make the proper changes to the prop.

1980 Swanson 42 Fibreglass Cutter - Boats.com

[GILow]

I don't know what sort of HP the 3404 produces, but I have certainly seen plenty with around 75HP engines. The boat you have linked interests me in a number of ways, not least of which is that they have completely ruined what for me is the most attractive part of the boat, the deckhouse, by removing the rear windows and leaving it open to the elements. Down in Tasmania of all places too. I could understand that near the equator perhaps... but not down at 40 degrees latitude.

Our boat had a Lysterfield (or some name like that) 50HP, but the original owner felt that was enough power and fitted the Nissan in 1986. He replaced the engine, gearbox AND propeller when he did so, I know this as I have the receipts. Interestingly enough, the whole lot, including instrument panel, in 1986 was $4500, which I guess was a lot of money at the time. Now unfortunately, the size and pitch of the prop is not indicated in the receipts, so there is a chance they were different and he changed the prop later.

The whole kit was supplied by Diecon who are a Queensland outfit who used to do a lot of this sort of marinisation, so you'd think between them and the original owner, that they'd get the prop calculation right.

It is so strange that their setup is so vastly different to the numbers coming out of the various prop calculators... I don't believe the understanding of boat propellers has changed THAT much since 1986...

Matt

[djmarchand]

Matt:

You have received a lot of good information in this thread but as always, some misinformation. It will be very difficult for you to sort out the difference.

So find the best prop shop that you can in your area. One criterion, but certainly not definitve is if they do computer scanning and can tune to Iso class I.

Then follow their advice.

David