Propsagain!

[Nasher]

With all the recent chat about props I’d be interested to hear what everyone thinks about my set up, I’ve always thought the prop seamed too small, however as the engine will be changed in about a years time I don’t want to spend loads of money trying different props.

Boat 6.25M Ocean
Engine 150HP Johnson VRO
Prop 15 x 17 Ali

Doesn’t exactly take off very quickly but I put that down to the size of the boat, bearing in mind I’m comparing it to my old Flatacraft Force 4 with a 55HP Suzuki.

With Two adults and 5 kids (6-8 years) on board it got up to about 38knots and dropped back to 35 with the throttle backed off so the engine sounds happier.
This unfortunately is the only data I have as I’ve only very recently fitted a GPS. There is No Tacho so I’ve no idea what revs its doing.

I don’t think I’m over revving at WOT it just calms down a bit with the throttle backed of slightly, having run a few tuned 2 Stroke bikes in the past you get an ‘Ear’ for when the engines happy. And as anyone that’s owned one of these engines will tell you, that backing off saves a lot of Wallet Abuse in the petrol station.


Nasher.

[Pete7]

Nasher

Without a rev counter any changes would be guesswork, unless you can find someone to hold a strobe light at the flywheel whilst you drive it at 38 knots.

What you need to know is what rev counters will fit and what the boat scrap yard in Bursledon has in stock (quite a few last week). Would be worth having a chat with Lee to see if any rev counter will fit or if it has to be OMC.

The scrap yard also have an ISO container full of props if you know exactly what your looking for. (Take a torch).

Pete

[Bilge Rat]

Nash

Pete's correct, you do need a rev counter, i replaced the busted counter on my old Evinrude with a standard 3 inch counter, someone told me that they dont need to be OMC and it did work.

[jwalker]

That sounds a bit slow for the boat/engine combination unless your rig is particularly heavy. You need to check wot rpm, soon.

At 5500rpm and 15% slip with a 17" prop you should be looking at only 34kn. With a 19" 38.7kn and with a 21", 42.6kn. The slip is a guess, if fact, with a standard Johnson ali prop it could be higher which would make the situation even worse.

I used to run a Johnson 150 and it was sweet at wot. One knew it was working hard but it didn't sound unhappy.

[Nasher]

Thanks guys

Pete, where is this yard in Bursledon? sounds like my kind of place.

Or does anyone have an old tacho lying around that they would exchange for some X-mas beer money?

I'm loathe to spend too much sorting it out as I'm determined to swap the engine this time next year, although I'm sure not running it at optimum revs etc is costing me fuel.

If I can sort out what revs its doing and end up getting hold of a more suitable prop then I'll have a more enjoyable season next year.

Nasher

[Pete7]

Nasher, start with the railway, crossing the A27 next to Aladins Cave. Go NE along a minor road for 500 yards following the river Hamble. You can't miss the scrap yard, think its called the barge but its spread over several hundred yards. The barge has the small items over two decks. Take a torch.

Pete

[Mark Halliday]

Pete

It it the barge that was Aladins Cave when we were both kids?

[Pete7]

No that was before my time

but yes its the barge, think the business is Foulks and sons.

Pete

[rads]

Here?

http://tinyurl.com/3sbgk

[Pete7]

Yep thats the one, you could probably go shopping there by rib

Pete