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post #21 of 25 Old 04-05-2016
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Re: old engine, new engine

We have a Cherubini Hunter 37 in the charter fleet, and a bunch of newer Hunters from 33-42 feet. They're all powered by Yanmar 4 cylinder engines. The Cherubini weighs in at close to 18K lbs and has a LOT of momentum when underway (I suspect that it may be under propped). The Hunter 41 displaces 19K lbs but will stop, comparatively, on a dime. While at the helm, I realize the difference, and adapt my technique to account for the differences. I teach my students to handle which ever boat that they're being trained on.

My O'day 35, with a 21 HP Universal M25, displaces 12K lbs. Under power, it handles like a sports car compared to the Hunter Cherubini 37.


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post #22 of 25 Old 04-05-2016
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Re: old engine, new engine

Quote:
Originally Posted by paikea View Post
Its a Bukh 10 HP, currently 40 years old. Seems to be in good condition, starts fairly well, but I need to be sure I can depend on it more or less. So these discussions are very helpful for me as it guides me into what to look into that of course at this point I am overlooking and additional things to try and do.
I had this same engine in a 28 foot boat. These are wonderful little engines. They are extremely easy to work on, extremely reliable, and a joy to own, although the parts are more expensive in the U.S. than the more common engines in the States like Yanmars.

When you talk about an engine which is not effective in reverse and an engine which is overheating, both can be symptoms of badly fouled propeller. When marine growth (barnacles, and other mollusks) attached to the bottom of the boat and the propeller, these can create greater resistance and reduced effectiveness for the propeller and so over work the engine, causing the engine to run hot, and reducing its effectiveness in reverse.

There are couple things that I would check if its not a foul bottom or prop. First of all, I would start with the water pump. The water pump impeller is pretty easy to change and should be changed every year since. As others have suggested, the mixing elbow can get easily clogged and cause overheating. I had to replace the thermostat twice in the 14 years that I owned my Buhk and do that would be another likely candidate.

I do not know if your engine has an outdrive or a conventional propeller shaft. My Buhk had an outdrive and that outdrive used a Gori propeller. That propeller was poorly made and would fail periodically allowing the inner hub to spin independently from the blade carrier. I would notice this first when in reverse since there would be an unnaturally long delay between the time I put the engine in reverse and the time that the boat seemed to respond.

My recollection is that these engines are geared differently in forward than reverse, and as others have noted, propellers tend to develop a lot more thrust in forward than reverse so you need to expect different performance in reverse than forward. One thing you do not want to do (since these are very torquey little engines) is to rapidly increase RPM (revolutions per minute- i.e. engine speed) since this can cause the propeller to spin ineffectively and not create much thrust in reverse. It is better to increase the engine RPM slowly and steadily as you feel the propeller grabbing and slowing the boat.

Unless there is something seriously wrong with this engine, which I doubt since it probably would not start or would sound awful once it did if there was a serious problem, I would certainly repair it or even rebuild it before replacing it.

Good luck

Jeff


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post #23 of 25 Old 04-05-2016 Thread Starter
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Re: old engine, new engine

@Jeff_H

You just described my little engine! Thats it, seems to work quite well forward but in reverse its like a different engine.

One thing now I am sure I am guilty of - I might have not been so gentle and lady like on that gear stick. I am starting to understand that. I think I might have gotten worried when I saw its lack of response so would push or pull the gear quicker especially when boats were all over around me, and a nice all glass restaurant.

"I do not know if your engine has an outdrive or a conventional propeller shaft."
Now, that I dont know whats called. See diagram I used when winterising the engine. I dont know if thats called outdrive or conventional propeller shaft. I presume when you say shaft, you mean the arm between the engine and the propeller.

I think I am becoming a professional mechanic with all of you around!
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post #24 of 25 Old 04-05-2016
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Re: old engine, new engine

part of my lesson: "When shifting, the engine should be at idle. Say the name of each gear (to allow the transmission to idle) when you put the shifter in that gear. Going into reverse would sound like this; throttle down, put transmission in neutral, say "Neutral," put the transmission in reverse, say "Reverse," throttle up.


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post #25 of 25 Old 04-05-2016 Thread Starter
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Re: old engine, new engine

@eherlihy

Obviously I wasnt doing that, quite like that! I admit it. I think I was going a bit too fast between forward and neutral.
This engine might be a blessing in disguise teaching me patience and delayed gratification when I use the gear and not only, but overall when I sail the boat. Of course I am still still at the stage that I feel nervous in certain aspects. That doesnt help. I know no one at the marina where I have my boat, so trying to doing things alone.

Thank you.

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