My 102 won't rev out
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My 102 won't rev out
Hi All. I have an old (1964) 102 that I bought from a local market for A$80. Great little motor but I can't get it to rev past half throttle under load. I have cleaned out the carb but not much has changed. It is only pushing a 9 foot flat bottom dinghy, so it should get along OK. Any ideas?
Must be time to get out on the water!
Ian
Ian
With a 102 myself, and similar queries in the beginning, I believe you are at the maximum hull speed for your boat, meaning, that a higher revving motor, or even a larger engine, would not push it any faster. (See naval design and the many posts on this matter in Seagull Forums for more info). The motor, the boat, and the water are all "maxed-out". If the motor revs fine in neutral, or in a tank, or with the prop off whilst in the water, then that proves the point that the "problem" (ie your desire to have it rev faster under load) is not in fact solvable. Sorry!
Therefore, when travelling, you only need the throttle at half-set (or a little bit less is better) or else you just suck fuel and load the motor with oil for no more outcome.
Therefore, when travelling, you only need the throttle at half-set (or a little bit less is better) or else you just suck fuel and load the motor with oil for no more outcome.
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CatiGull
- Posts: 267
- Joined: Sun Mar 12, 2006 2:35 am
- Location: Delmar on Hudson NY USA.........3000 nm west of THe Black Country
Ian - take a look in the carb bore and make sure the throttle piston (brass, about 1 cm in diam) is fully retracting into the carb body (it should move up) so that it completely uncovers the bore at full throttle.
If it doesnt, then that is your problem.
On the VIlliers carb (so labelled) there is a knurled nut on top that will allow for some adjustment if the cable looks ok.
I had a old butchered cable on one of my Gulls that someone had jury rigged with wire, etc - I finally bought a new one from john for a pittance and then it worked beautifully. Since many Gulls dont have clutches it is important for boat handling to have it working correctly if you have to maneuvre in tight quarters
If it doesnt, then that is your problem.
On the VIlliers carb (so labelled) there is a knurled nut on top that will allow for some adjustment if the cable looks ok.
I had a old butchered cable on one of my Gulls that someone had jury rigged with wire, etc - I finally bought a new one from john for a pittance and then it worked beautifully. Since many Gulls dont have clutches it is important for boat handling to have it working correctly if you have to maneuvre in tight quarters
Stephen
Awenke Yacht Club
New Baltimore NY
S/V Catigale
Macgregor 26X
Island 17 Sloop
Awenke Yacht Club
New Baltimore NY
S/V Catigale
Macgregor 26X
Island 17 Sloop
Thanks Guys. Carbie was fine, made up a new cable for it. Cleaned and set the points (they were set to about 10 thou). Started and ran great but no change in speed. From what I can find out the potential top speed for my hull is about 4.5 knots, which felt about right , I don't have a knotometer so I don't know exactly. I'll forget about buying waterskis for now.
Must be time to get out on the water!
Ian
Ian
Hi Ian.
I only learned this fact (re the maximum hull speed) through browsing the Seagull Forums. Somewhere .! ? ! ? ... I saw an equation for the maximum speed relative to boat legth (well waterline length, actually). No doubt one of the the old mariners lurking here could tell us.
This cause being established, the trick is now to make sure you "trim the dish", that is distribute the weight in the boat so that it is even front and back, left to right, which gives you the maximum hull speed, rather than sitting at the back and having the nose in the air, which definitely slows you down. I have rigged a set of cables on my little 12' dinghy so as to be able to sit in the middle seat facing forwards and steer the motor which is 1.5m behind me.
Good luck.
I only learned this fact (re the maximum hull speed) through browsing the Seagull Forums. Somewhere .! ? ! ? ... I saw an equation for the maximum speed relative to boat legth (well waterline length, actually). No doubt one of the the old mariners lurking here could tell us.
This cause being established, the trick is now to make sure you "trim the dish", that is distribute the weight in the boat so that it is even front and back, left to right, which gives you the maximum hull speed, rather than sitting at the back and having the nose in the air, which definitely slows you down. I have rigged a set of cables on my little 12' dinghy so as to be able to sit in the middle seat facing forwards and steer the motor which is 1.5m behind me.
Good luck.
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CatiGull
- Posts: 267
- Joined: Sun Mar 12, 2006 2:35 am
- Location: Delmar on Hudson NY USA.........3000 nm west of THe Black Country
Its approximately
4/3 * Square root (waterline length in feet) gives you the hull speed in knots
so hull speeds for some waterline lengths look like
Water line in feet Calculated hull speed
9 4 knots
16 feet 5.3 knots
25 feet 6.7 knots
You can extrapolate your boat size in between these data points if square roots hurt too much
4/3 * Square root (waterline length in feet) gives you the hull speed in knots
so hull speeds for some waterline lengths look like
Water line in feet Calculated hull speed
9 4 knots
16 feet 5.3 knots
25 feet 6.7 knots
You can extrapolate your boat size in between these data points if square roots hurt too much
Stephen
Awenke Yacht Club
New Baltimore NY
S/V Catigale
Macgregor 26X
Island 17 Sloop
Awenke Yacht Club
New Baltimore NY
S/V Catigale
Macgregor 26X
Island 17 Sloop
what happens
when a boat is sailing, it is making a wawesystem, one wawe in front, and one at the rear, there is not much water in the middle, so you are sailing on the two wawes, that's how it is, until you try to exede top speed of the hull, and sail away from the rear wawe, then there is no lift to the rear end , and it will sink, and the speed will not increase, specially if your weight is placed there. Unless you have a planning boat , with power to sail away from the wawe and keep it far behind the boat. The speed will lift the rear end .
Law of nature.
I know it's not english, but I hope you get the meaning.
Law of nature.
I know it's not english, but I hope you get the meaning.
Gentlemen, I accept your answers as truth and thank you for your time. I know nothing of hydrodynamics and find it hard to understand how a longer (and therefore heavier) hull will go faster than a smaller one when both are pushed by the same motor. On a similar subject, I have read that a long canoe is easier to paddle than a shorter one. Same thing?
Must be time to get out on the water!
Ian
Ian
yes
It is all about length, and selfmade wawes, if you could find a pic. of a moving boat you will be able to see the wawesystem. But you are right, if the boat is planning on the water. Then the law of the wawes is not active. 
about the canoe I think the longer form, makes it harder to turn, so your efford will make speed instead of turning the canoe, and the rule of the wawes is working as well.
It also goes for sailing boats, they loose stability, because there is not much water where they are broadest, so a boat, broad on the midlle is not neccesery stabil, broad in the rear where the wawe presses is more stabil.
To days boats have a broad rear end. That's makes it easier for it to surf on big wawes too.
about the canoe I think the longer form, makes it harder to turn, so your efford will make speed instead of turning the canoe, and the rule of the wawes is working as well.
It also goes for sailing boats, they loose stability, because there is not much water where they are broadest, so a boat, broad on the midlle is not neccesery stabil, broad in the rear where the wawe presses is more stabil.
To days boats have a broad rear end. That's makes it easier for it to surf on big wawes too.
see it
If you go to SOS and history side there is a little ad. with a wooden boat and a B.S. It shows the wawe system.