Alpha one propeller

[Paul_1975]

Hi I've just joined the forum, I bought a 1995 rinker fiesta vee two years ago. As I live in Ireland gas is expensive and not readily available on the water so the previous owner changed the petrol engine to an Isuzu turbo diesel retro fit! I'm sure this is sacrilege to you guys but the problem I'm having is low speed wander as the engine is high torque low revs. I'm thinking a prop change would help, any ideas on what to go for pitch, size, number of blades to suit a low revving diesel?

 

[alldodge]

low speed wander

Howdy

If this is happening at idle then this is normal for a V hull and has nothing to do with the prop. If you have trim tabs you can lower them some and it will help. You can find a place to put the helm where the boat will just go left then right about the same anmount.

Nothing wrong with diesels, they even put them in offshore racers

 

[H20Rat]

the previous owner changed the petrol engine to an Isuzu turbo diesel retro fit! I'm sure this is sacrilege to you guys

Pics? That is actually really cool, would love to see some small turbocharged diesels ending up in boats over here, just hasn't happened.

But yeah as dodge mentioned, wander is a characteristic of the hull, not the prop. Trim tabs/smart tab can often help, as well as just learning how to not overcompensate.

 

[thumpar]

Sounds like a nice setup. The wonder is normal. Just try to not over correct for it. I mostly just let mine wonder unless I am in a really tight spot. It evens out in the end.

 

[Paul_1975]

Thanks alot for the replies guys, the engine is from a 2.8 litre Isuzu trooper jeep. I'm thinking the guy who marinised it governed the engine to the suit cooling the engine, at WOT it's only about 2800 rpm and I'm only getting about 10 knots max with the boat wandering from side to side which I've got used to. I reckon if the boat was going slightly faster this may disappear so no point in going for a bigger/ different pitch prop? I'll get some pics

 

[thumpar]

Being a one off setup it is hard to say if maybe the prop is just not pitched high enough or maybe the drive ratio doesn't work well for that engine. If you have access to a higher pitch prop it is worth putting on and see what you get for speed. If you could get it to plane out the wonder would go away and you would get much better fuel mileage.

 

[Bondo]

Hi I've just joined the forum, I bought a 1995 rinker fiesta vee two years ago. As I live in Ireland gas is expensive and not readily available on the water so the previous owner changed the petrol engine to an Isuzu turbo diesel retro fit! I'm sure this is sacrilege to you guys but the problem I'm having is low speed wander as the engine is high torque low revs. I'm thinking a prop change would help, any ideas on what to go for pitch, size, number of blades to suit a low revving diesel?

Ayuh,..... Welcome Aboard,...... What prop is on it now,..??

Is it the 3.0l drive, with the 1.98:1 gear ratio,..??

I Love diesels, 'n think it sucks their not found much in boats, 'n cars, in the USA,....

 

[Paul_1975]

Thanks for the replies and the welcome! I need to look for the numbers on the prop Bondo, I'm going down to boat yard on Saturday the drive serial number is oc819843 and I think the boat was originally fitted with the 5.7 mercruiser engine. The prop I have is a little damaged its 12" in diameter and I'm hoping a slightly bigger prop may suit the high torque low speed Diesel engine.

 

[Bondo]

and I think the boat was originally fitted with the 5.7 mercruiser engine.

Ayuh,..... This May, work out to yer advantage, or not,......

Bein' a low revin' motor, yer gonna need taller gears to get any speeds,....
The V-8 ratio is 1,50:1, the I-4 ratio is 1,98:1,......
There's also a 1.65:1 ratio, 'n a 1.84:1 ratio available,....

Standard prop diameters should run in the 14" to 16" range,.....
12" sounds like a too small outboard motor prop,..... which it could be,....
The mid-sized gear case Merc outboards run the same size prop shaft, but skinnier gear case,....
It'll bolt on, 'n run on an outdrive, but ventilate, Badly,....

 

[Paul_1975]

Thanks very much for the info, changing the ratio setup would be a major job? Had quite alot of fun changing the bellows really glad we did as the cooling water hose just fell off someone had neglected to use a stainless jubilee clip. Apart from the temperature gauge are there any other "tell tale" ways of checking the engine is getting cooled? I'm used to outboards

 

[achris]

Sounds like PO governed the engine and trimmed the prop. I would suggest you remove the governer and get a full size prop on. Find out at what rpm the engine is making full power and then do some prop trials until you find a prop pitch that only allows the engine to get to max revs at full throttle.

good luck. . ...

 

[Paul_1975]

Good advice thanks achris! Here's a pic of the engine it's probably done starship road miles before it was marinized but starts on the button, no smoke and very fuel efficient at the expense of speed!