Thread: Boat Questions

Here goes my first of many (no doubt)
My boats outboard motor came with two SS props , a 17 & a 19 . I was thinking of running the 19 , but wondered if I was doing a lot of trolling, which prop would be at a guess more efficient ? .

The 19 would should be more efficient
With the 17 on the motor will be carrying more rpms for the same speed but get there quicker.
Think I got that right......

17 faster screw in the water and faster out of the hole, but depends on HP. And boat size. Try both I ran a 21" SS on my 130 HP and it was a dog I have a 5.6 metre Sea Nymph. Run a 19 on it now. Also make sure revs are right for the engine at top end, might be some thing in the manual.

yep the best prop is the one that runs out at wide open throttle in the correct revs.
depending on the motor it may be 5400 to 6000
look up the specs for your motor and see.
then, take both props to the lake on a calm day, stick them on one at a time and give it a test run.
you may also find the 19 runs too fast at idol to trawl so check the minimum speed.
is it a 2 stroke? premix, they dont like to idol along all day, a small aux motor is often a better bet for putting about.
greg
greg

Yep check max rpm range for motor and ensure it will pull max rpm( in the range) trimmed up as much as possible before ventilation/cavitation.
If it wont pull up to its max rpm range the prop has to much pitch and should not be used(providing motor height and trim optimum) as it will be loading the motor.
The 17 should give better holeshot for pulling skiers etc or heavily loaded running.

Depending on troll speed it would be a tough call which would be more efficient especially at game fish trolling speeds which generally is about the most ineficient speed you can push a planeing hull at

Originally Posted by greghud

yep the best prop is the one that runs out at wide open throttle in the correct revs.
depending on the motor it may be 5400 to 6000
look up the specs for your motor and see.
then, take both props to the lake on a calm day, stick them on one at a time and give it a test run.
you may also find the 19 runs too fast at idol to trawl so check the minimum speed.
is it a 2 stroke? premix, they dont like to idol along all day, a small aux motor is often a better bet for putting about.
greg
greg

Sorry Greg , I'm talking gamefish trolling in the sea , like Cam says its by far the most awkward speed you can do . It may be a case of trial and error to find whats the most efficient . Its a two stroke but the VRO model , I believe the oil is adjusted by the revs .

haha, i had trout on the lakes in my mind.
still the same rules apply for the prop set up, but for a high speed trawl i would think the 17 with a higher rpm would give you better torque and it will hold the speed better, but as for fuel use? only a actual run with each will tell you.
good luck with it!
greg

Get. Variable the pitch prop, there fixed your prob.

You would troll pretty fast for that, compared with trout at about 1.7 knots. Try the 19 as it's usually a long way home and you need speed and fuel economy as well, VRO will take care of itself!

Munsey, I troll 6-7 knots (when I get the chance) and my fuel economy is rubbish with my 150 2 smoke, about 14l/ph I think when trolling. (Just put a hat over the gauge, if you can't see it its not happening .

Most comfortable ride/speed in my boat is also not the most economic rpm for fuel burn.