posted 09-17-2008 04:28 PM ET (US)        

---

Swiftly cut back the throttle on a big displacement craft, especially a sailboat powered by a little motor, and the boat will keep its momentum, glide forward and slow almost imperceptively; suddenly cut back on the power on the smaller Whalers and you might pitch someone right over the bows. We all know that, and we're warned in every outboard motor manual about the phenomenon--little outboard skiffs stop almost instantly when the power is cut back abruptly. I'm tossing out this topic not so much to discuss the safety factors, but to inquire about possible damage to the motor itself if speed is swiftly reduced. I've completed breaking in a little 60 hp four stroke on a 15-foot Whaler, and I've been even more compulsive than in the past about treating the motor gently (even though I've found myself running it at substantially higher revs than my other four stroke, mainly because I'm using the little boat on calmer waters than the previous ones, and I can't resist the higher speeds). Part of my new, gentler nature is a conscious effort to slow down very slowly indeed.

So what do you folks think--can an outboard motor be damaged by repeatedly slowing down swiftly? Seems intuitive that the force of the water during deceleration against the slow-turning prop can be injurious...am I missing something?

Tony

posted 09-17-2008 05:31 PM ET (US)         

---

Seems to me no different than shifting to a lower gear in your truck when descending a grade in order to get engine braking. I see no reason why the drivetrain and engine components would be more stressed decelerating than when accelerating.

But I do share your feeling that machinery should be treated kindly. The owner's manual for my old BWM motorcycle (obviously translated from German) noted something to the effect of, "whilst the vehicle is capable of rapid acceleration and deceleration, it can present a penalty through faster wear upon engine and brake components. "

posted 09-17-2008 06:36 PM ET (US)         

---

Back in the old days, 1930`s-1940`s when you and I were young, rapidly slowing down a speeding outboard would cause the engine to kick out because of resistance in the water. Then if you immediately gave it throttle, the motor would kick back against the transom with a loud THUNK, That could crack your transom, although the motor would not be damaged. That would be the only damage that could be done by slowing down rapidly.

rich

posted 09-17-2008 06:44 PM ET (US)         

---

Tony, I forgot to add that OMC, in 1951, put a reverse kick out lock an all their larger engines, so this phenomenon could not happen. I haven't worried about this for about 57 years or so.

Its a slow day today here in my newsroom since jimh deletes all political news, LOL

rich (as frisco pete)

posted 09-17-2008 07:01 PM ET (US)            

---

I slow down slowly until I start to fall off plane, then back off quicker. My goal is to get the farthest I can through the water with the least amount of fuel used. I have no idea if I am saving any fuel by doing this, but I do not get very good fuel economy at slow speeds. I try to be smooth, like I drive my car.

That's in the big boat, in the small one I am all over the board.

My buddies Mercury will "click" if you slow down quick. I think it is the propeller ratcheting on a clutch of some sorts.

John

posted 09-17-2008 08:19 PM ET (US)            

---

"Find something else to worry about," suggests 2manyboats. Well, that's not very hard to do today, is it, with the $85 billion AIG bailout, the stock market in free fall, down 23% since this time last year, Ike and its aftermath, new building starts down 6+ percent and permit requests off 9+ percent...let alone the presidential election situation (I can say no more about that, but she believes that dinosaurs roamed the earth 4000 years ago, God help us).

Tony

posted 09-17-2008 08:40 PM ET (US)         

---

Tony,
Thanks for putting things back in perspective. One other thing, the dinosaurs died off becuase they were to big to fit in Noa`s Ark. I was told this by a believer. This might not be Whaler related, but it is boating related. Not political at all.

rich

posted 09-17-2008 08:49 PM ET (US)            

---

I wish I had "2manyboats". Tony, decide where you want to come off plane, back off so she "settles" off plane, then go about you idling/no wake business.

It's kinda like a stop light. Anticipate. Hey, it's not like we're 20 anymore. The wife at one's side will not be impressed. She likes "smooth..."

How do they do it in Alaska? Ram the dock and pitch the b**** out! Quick and dirty...

posted 09-17-2008 09:21 PM ET (US)            

---

Bob,
Thanks for your insult. Remember, us "Rednecks" in Alaska know nothing of boats. What is a boat let alone a Whaler?

Tony,
I would not be concerned at all. I'm sure you're more than competent in that 15. Heavy following seas would be my only concern. Take care, Mel.

posted 09-17-2008 09:30 PM ET (US)            

---

I'm not really all that concerned, Mel, and all of us who put in some time offshore north of San Francisco develop a certain level of competence surfing following seas in our classic Whalers, but my question really had to do with possible damage to one's motor by sudden deceleration. I think I've got the answer.

Tony

posted 09-17-2008 09:38 PM ET (US)            

---

AK,
My apologies about the Alaska remark. Wasn't directed towards Alaskans in general. Just a certain state official.

Hope I haven't further offended anyone. Alaskans sure know how to handle boats. Get Tony's, and my, drift?

posted 09-17-2008 09:40 PM ET (US)            

---

"Back in the old days, 1930`s-1940`s when you and I were young..."

Thanks a lot, Rich. The sad thing is that you're not all that far off. I wish I could say that zipping around in a little 15 represented some sort of 'mid-life crisis,' but it's a little late for that, at least for me ;-(

Hold onto your hats, Whalers--it's gonna be a lumpy, windy, uphill ride for a while for most of us (but not for the Freddie Mac, Fannie Mae, AIG, Lehman Bros, Merrill/Lynch upper echelon execs; they're doing just fine, thank you very much).

Yikes! What an incredible mess.

Tony

posted 09-18-2008 06:44 PM ET (US)            

---

My propeller does NOT freewheel when decellerating. For a while there I was having problems with it dying suddenly while at high speed. When it would die, the propeller would continue to force the engine to turn and would cause the boat to decellerate very quickly, throwing me against the console. By pulling the throttle back to neutral, the decellaration was much more gentle.

Does it damage the engine? Hard to say, really. Probably not instantly. But suddenly reversing the forces acting on the main bearings can't be good for it over the long term. Also, I worry about the extreme suction forces acting on the trottle vanes. Could it cause one to break and get sucked into the cylinder? Doesn't seem very likely. I've never heard of it happening. But it sure seems like it's a posibility.

posted 09-19-2008 12:42 AM ET (US)            

---

What the hell is a trottel vane?

Maybe you should not have rebuilt the engine yourself if you do not know what a reed valve is????????

Second....4 strokes do not have either.

Oh friggin boy!!!!!

posted 09-22-2008 08:52 PM ET (US)            

---

Not so fast there, Frontier.

http://www.blog.newsweek.com/blogs/stumper/archive/2008/09/22/ the-boomerang-effect.aspx

I'll take Obama ANYDAY over the doddering fool and his "mate", either blonde or brunette.

posted 09-22-2008 09:56 PM ET (US)         

---

Back to the topic of slowing down quickly...I have heard from mechanics that it is possible to have an outboard ingest seawater through the exhaust system if an engine is slowed down too quickly. Not sure if this is true though, anyone that knows more about these matters care to comment?

Generally I try to slow down slowly enough that water does not come over the transom or outboard.

posted 09-23-2008 02:15 PM ET (US)            

---

"bigshot",

Sorry, I made a typo. I meant to say "throttle vane". This would be the disc shaped piece of metal in the carburetor that meters the amount of air that flows into the engine. Any carbureted, or even fuel injected engine, whether it be a two or a four stroke engine, has them. Were it to break under intense suction (which, I admit, seems very unlikely), the pieces could potentially pass through the reed valves (or intake valves on a four stroke) and into the combustion chamber.

Sorry, I didn't realize that fogetting an "h" would cause you to become such an asshole.

posted 09-23-2008 02:21 PM ET (US)            

---

20dauntless,

I could see that happening on a 2 stroke. If high pressure in the through-hub exhaust caused water to come up the exhaust, a small amount could conceivably enter a cylinder if it caught it at just the right moment on an intake stroke, or if the engine had stopped completely with the cylinder in such a position that both the intake and exhaust ports were "open".

However, it would have to be a lot of backpressure, and I don't see how it could be enough to cause it to hydrolock.

I really only see it happening if, for some reason, the engine suddenly seized for some other reason.

posted 09-24-2008 01:32 PM ET (US)         

---

Frontier, You ahould get your facts straight.

http://voices.washingtonpost.com/fact-checker/2008/09/obamas_fannie_mae_connection.htmlrontier

posted 09-24-2008 01:44 PM ET (US)            

---

I was just pulling your leg!

Do you mean the butterflies? Would be nearly impossible for them to break off.

posted 09-24-2008 02:12 PM ET (US)            

---

Sorry if I took your comments a little too personally.

I agree, it seems extremely unlikely, I was just thinking it might be possible. Your analogy to an automobile is a good one and makes a good point. Seems impossible, or at least they are engineered strong enough to withstand such forces. So, no, I guess that isn't something one needs to worry about. However, in a 2 stroke motor, what about the lack of fuel/oil being sent into the engine to lubricated it while decellerating? I suppose it's not enough of a problem to warrant worrying about it. Still, slow decelleration seems like a good idea anyway, for a number of other reasons.