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ContinuousWave: Whaler Performance
Are you Watson or Holmes?
|Author||Topic: Are you Watson or Holmes?|
posted 03-24-2004 01:39 PM ET (US)
As I mentioned in my 'rant' a few days ago, I had a funny thing happen on the way in from fishing last week. I will describe the scenario in as much detail as possible.
I had just passed the R/SR bridge and was heading south with the current and into a 20-25 mph wind that was tacking from the southwest. I had taken a few bad jumps on the waves and decided that I would turn into them, and trim the engine in all the way. As I did so, I compensated with the throttle to keep my speed at approx 16-18 mph. The waves were stacked due to the current, and this made it dangerous to tack into them. I had one decent wave bring me to half speed as the bow plowwed into the wave, this happened several times, and at one point, the prop seemed to have lost grip, and I noticed that the engine started to decelerate, as if it was running out of fuel. I advanced the throttle a bit to keep the engine at speed and reached down and checked the weight of the current tank, it was heavy so I knew I didn't run out of gas. As the loss of power was continuing, I throttled down, then back up, and felt that though the engine would rev, there was little forward motion, and that the motion was not consistent with the engine speed. At this point, I assumed that I may have spun the prop hub, and was not sure what to expect. I took a chance and revved the motor briefly. As I did this, I noticed very little forward movement, with a very harsh and noticeable vibration from the engine, It maxxed out at about 4000 rpm. I brought the engine back up to about 2000 rpm and noticed enough forward movement that I could limp into some protected water. As I was approaching the protected area, I slowly raised the rpm's and the problem seemed to have dissapeared. Once in the protected water, I raised the engine enough to look at the lower unit, it seemed fine. I ran the risk of going back to port, though I knew I would have to go through one more rough spot. The problem never showed again, and I once back near port, I took a few laps around at higher speeds. I noticed that trimmed all the way in, max speed was about 4500 rpm, Trimmed half out, about 5100 rpm. It was too rough to test trimmed fully out, but the other positions showed performance that was consistent with previous tests. Yesteday, I pulled the plugs and the they too seemed fine, Top was clean wet and light tan, Mid was clean wet and a bit darker, Bottom was a bit dirty, brown and wet.
So, be it Watson, or Holmes, judging by the above mentioned clues, what do you suspect caused the situation? Motor is a carburated 2 stroke. Locals may have a bit of an easier time at this, but that in itself is another clue.
posted 03-24-2004 01:48 PM ET (US)
You are probably more experience than me but I'll through out a few ideas....
1. Vent closed on gas cap or perhaps all the jostling around caused some type of bubble to form in vent or a blockage.
2. Fuel filter - maby not completely clogged but all of the jostling around caused temporary blockage.
3. More of a following sea than you realized.
I guess in the right conditions #3 might cause unexpected vibration as the motor tried to work against a lot of competing forces.
posted 03-24-2004 02:11 PM ET (US)
posted 03-24-2004 04:14 PM ET (US)
Landlocked, it was a head/starboard sea that I subsequently turned straight into.
Buckda, no kelp in SF Bay.
Good tries, keep going.
posted 03-24-2004 04:25 PM ET (US)
It's Watson for me. But for different reasons.
It is my wife's maiden name.
"Come here Watson, I need you!" Has a whole different meaning in this household :-)
posted 03-24-2004 05:01 PM ET (US)
Last year my son and I went up to meet a friend of mine at the lake with his new boat. It was early spring and the water had just come up to full pool after being down for a long time. When we decided to go in I dropped him off to get the trailer and took the boat out for a little spin on the way to the ramp. Well, about half way through my test run of his boat, I began experiencing the same thing that I think you were experiencing. I would give it gas, rpms would increase, but would not get much forward motion. I was really worried. We were the first people ever on his new boat and it seemed that I had broken it. Anyway, not knowing what else to do, I put it in reverse to see what happened. The boat backed right up and guess what floated out from under the front of the boat, a 2x6 about 4' long. I think it must have gotten lodged so that it was acting as a brake in front of the motor. After the obstruction was gone, the boat ran fine. We checked it out at the ramp and didn't find any damage. It could have really been a mess.
posted 03-24-2004 05:37 PM ET (US)
Salmon Tub- I had experienced similar problems with my Yamaha when I got into heavy seas. The problem was resolved when I added a fuel/water seperator. pete
posted 03-24-2004 05:42 PM ET (US)
Your prop ventilated & an air pocket wouldn't allow the blades of the prop to re-bite.
What you needed to do was, stop the boat, put it in neutral, [ not mandatory ] to allow the air to escape & come to the surface, then put it back in gear.
Once you vent the prop, the air pocket will stay with the prop as long as it's turning fast enough.
I know exactly where you were & this would happen while heading into the waves, not in a following sea.
In many cases, this will burn the pain off your prop & could pit it,....very common.
posted 03-24-2004 08:46 PM ET (US)
Oooo! Sal, very interesting hypothesis. But, don't forget to take into account, the vibration, the loss of power. That was the second thing that came to mind after the thought of a spun hub.
Kelly, interesting, That was the third thing I thought of, but nothing quite as big, but remember, I did not notice anything funny after I raised the lower unit when I got to the calmer water.
Things are starting to get interesting, and informative, this is almost like an episode of Unsolved Mysteries! ;)
posted 03-24-2004 08:50 PM ET (US)
Pete, didn't mean to ignore you, My engine has a stock, though small, fuel filter/water seperator under the cowling. Though the ride was rough, I do not recall ever having any major pitching, outside of the realm of normal, which would account for some accumulated water getting drawn up into the line from the filter.
posted 03-24-2004 09:14 PM ET (US)
Having two tanks myself here is my guess:
You picked up the wrong "current" tank. The real current tank was near empty. Jim
posted 03-24-2004 09:37 PM ET (US)
ST, the vibration is 1 or 2 of the blades catching water but the other[s] still spinning free because of air, thus the vibration.
As far as a loss of rpms, I've had engines drop rpms or even die after hitting a hard wave like real hard [ not with this engine ] ,.....why,....I can't tell you because it's a secret, such a good secret that I don't even know.
My guess is, your engine is mounted to high for the rough water or ocean, such as mine when I run her up on the 3rd set of holes on the ocean, she will break loose,....so when going on the ocean, I drop the engine down a set of holes & drop back to a 19p prop from a 21p prop.
This will cure your problem.
In your case, the ocean or a very, very rough piece of water, you really need to drop her back down a set of holes or use a prop with 2" less pitch for either the ocean or if you know it's going to be rough.
If your set up for maximum performance, such as top end speed & the engine mounted way up, you will have a problem when you hit water like you did.
I say this because mine will do the same as yours if I don't re-do the height of the engine & less pitch in the prop.
posted 03-24-2004 10:51 PM ET (US)
Last summer, I had a similar problem but without the vibration. We were zipping across the Delaware Bay at 40 mph. The water was as flat as glass. All of a sudden, the motor sounded "funny" and the speed dropped off to about 25 mph. I could get the motor RPMs to increase normally but the speed wouldn't go over 25. I was thinking that maybe the hub had spun in the prop. After a few minutes of running like that, we stopped the boat and raised the motor to see if we could find the problem. There was a split in half 1/2 gallon milk jug hung up on the nose of the lower unit. We had picked this thing up at 40 mph and it must have really ruined the flow of water to the prop.
You could very possibly have picked something up that was interrupting the flow of water to the prop. Or, as was suggested earlier, it could have been a cavitation problem too. I don't know though if cavitation is as strong a possibility if conditions were as rough as you describe.
posted 03-25-2004 12:40 PM ET (US)
Kudos to Sal and Ron. Both of those theories are exactly what I had boiled it down to. I have decided that it was 1. either air just as Sal described, or
2. due to the time of year, I had ran into a rather common though non indiginous species that migrates through these waters this time of year - the discarded plastic bag. They come through the bay often at this time. Later in the year, they are easier to spot since the water is clearer and they float just under the surface, like a jelly fish.
Sal, one thing about your last post does disapoints me, very deeply. Since I had gone through the hassle of raising my engine one hole last year, I do not wish to go through that excersize again in the near future. Instead, I think that I will just live with this experience, for now. I may consider the addition of a hydrafoil on my outboard.
I thank everyone for their input, and perhaps this thread can now help others in the future to diagnose a condition should they experience a similar situation.
posted 03-25-2004 08:13 PM ET (US)
A very interesting thread indeed. Many thanks for this contribution. I am certain it was enjoyed by many more readers than those who participated directly.
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