Engine refit

[chainyank]

EDITED TO SAY - False alarm. There is not problem after all, but I will finish posting some images of the engines, and leave this thread for the ages....... Sorry for any trouble, read the post with all the pictures and you will see why.....

Hello, picture tomorrow, question tonight....

I finally had time to start looking at what needs to be done to fit my new engine, an Albin AL-23, into the slot the old one sat on. The "new" engine has a crank start mounted between the engine and the transmission. This builds the length of the engine by about 5 cm. This in turn makes the prop stick out 5 cm. This was a sad discovery, when I was so happy to have a crank start "bonus pack" on this "new" engine.

My question: what is the best to do, keep the engine mount the same, and cut 5 cm off the propshaft or cut more out of the motorbed and reset the mounting bolts and move the whole deal forward 5 cm to put the back of the transmission in the same place as the old?

I am still new to inboards and couldn't find any search results, so figured its time to ask. what is the least bad thing to do, I am not happy about this, I had planned to be able to drop the new in the old space (but it is never that easy is it?). Anybody have this kind of problem?

I'll have pics tomorrow, it is a real old beauty....

[wet-willy]

I'm no expert in boats.Kinda learning as I go.But,going by your description,I would be inclined to relocate the engine mount holes.5cm off the shaft might mean having to rebalance the shaft or else you'd be stuck with a potentially nasty vibration.

[The Bigfella]

I don't know what sort of boat you are talking about? Small, medium sized at a guess? I'd be inclined to shorten the prop shaft and keep the engine (read weight) in the same place.

Just noticed the previous post, sorry, don't agree - there is no balance issue that comes into play here. The only issue is how the front flange (or perhaps the prop - depending...) is joined to the shaft. On my smallest boat, it is simply a matter of two lock bolts into a depression in the shaft. On Grantala, it is a tapered 2" shaft ... and that is major work.

[chainyank]

hey there Bigfella,

I have a kosterboat 7.6m x 2.85m
http://farm4.static.flickr.com/3513/3289224644_065972ee7a.jpg?v=0

I will get pics of the new and old engines today.

I had thought about the issue of weight if moving the engine forward, and that is what made me think of cutting the propshaft.

The prop is grabbed at the front by a flange which inturn bolts to the flange coming off the transmission.

How hard is it to cut the steel propshaft, if that end up being what I should do?

[The Bigfella]

Its easy to cut it. The question though is, how does the flange locate on the shaft? Is it a tapered end on the shaft? A spline? Either of these will mean you will need an engineering shop to do the work.

[D Happ]

Have the propshaft cut and also get a drawing made so the next time you need a shaft, you know what you need.

[Gary E]

Dont most low powered transmissions connect the coupling to the shaft with a KEY and a couple of setscrews ?

Do NOT move the engine for a lot of reassons...

And since you asked how hard it is to cut the shaft, it's best you just take the shaft and the coupling to a machine shop where they will cut the shaft off 5 cm..(that's a whole 2 inches and not much) and extend or recut the keyway so the coupling will be positioned in the proper place.

[Lew Barrett]

Whenever you select new power, that is change the type of motor, it is likely that
the weight and balance equations for the boat will change some. Going from gas to Diesel, for example, invariably will mean adding weight and fussing with the mounting arrangements. Some weight may shift forward a bit, or some may shift back. Engine mounts and shaft couplings are also likely to vary. All of this can be accounted for with a bit of careful consideration.

So I'll offer you a third possibility, depending on how thorough you want to be.
I'd consider what is the easiest way to attack this problem, what retains the easiest access for future maintenance and how much any shifting of weight will affect your trim. If all of those items are found to be about equal; that is, weight and trim issues will be unaffected, and access for maintenance isn't much a factor, then pick the solution that is easiest and most cost effective for you to accomplish. A couple of inches of shift in weight one way or another with a relatively light "auxiliary" (she is a sail boat, after all!) motor across a 25 foot (approx) boat probably isn't a deal killer. Do the easiest solution unless there is something you haven't told us that drives this decision clearly in one direction or another. Probably as or more important than this factor is what sort of engine mounts you plan to use.

Maintaining precise weight, trim and location during a re-power project is going to be difficult indeed unless you are replacing with exactly the same sort of power plant.

[chainyank]

thanks Lew,
It is an exact copy of the old engine, only with this crank start added in the middle, otherwise everything is the same.... I just got home with pics, so I'll get them up soon...

[seo]

I'd leave the engine where it is, all things being equal. You say that the shaft is "steel." Are you sure? Not bronze? Well, maybe stainless steel.
The shaft is most likely located on the coupling flange with a key in a milled-our keyway, maybe a couple of setscrews too.
It's possible that the keyway already in the shaft is long enough that you can cut 5cm off the nose and still have some keyway left to work with. In that case, you can cut the shaft off with a sharp hacksaw blade. Otherwise, you're off to the machine shop, because cutting a keyway is done with a milling machine.

If the shaft has to go to the machine shop, you might as well send along the flange as well, so that they can make sure that the fit is correct, and the flange face is true.

Also, when fitting the flange, made sure you drill proper "dimples" in the shaft for the setscrews to nose into. This is what keeps the shaft from backing out of the flange when you're running in reverse.

Before doing all that, I would check to see if you'll be able to reach the hand starting crank. I've seen the type of chain-driven crank you seem to be talking about on Sabb engines, and they seem to have been designed for use in open launches. They often have to be modified to work on a sailboat with cabin trunk and bridge deck. If that's the case, and if the hand start is an important feature to you, they you'll want to think out how it's going to be modified to work in your boat. That might involve moving the engine forward, or back.
From the look of your boat in the picture, moving a couple hundred pounds of weight back or forth a couple of inches isn't going to have much effect on her trim. All things being equal, keep the heavy weights at the center of her buoyancy . That's where they'll have the least effect on her pitching moment...
SEO

[chainyank]

So I went to get pictures of the old motor in the computer files and made an interesting discovery, or rediscovery. The old engine had the "insert" but the crank arm wasn't mounted, so the engines are the same length after all...... In the year that has gone by since having the old engine in the boat I forgot that it had that insert with the "arm" di-mounted.... umm opps. Well have a look....

The "old" engine.....
http://farm4.static.flickr.com/3635/3477763772_121072a34d.jpg?v=0
in the boat

the transmission....
http://farm4.static.flickr.com/3395/3477764318_28c3786970.jpg?v=0
here you see the "pill" shaped cap on the crank start insert.

The "old" engine out of the boat....
http://farm4.static.flickr.com/3356/3477766552_f4f6d299b5.jpg?v=0

The "new" engine on the way in when I thought there was a problem....
http://farm4.static.flickr.com/3339/3477767948_4b95d594e1.jpg?v=0
and a close up of the insert...
http://farm4.static.flickr.com/3547/3477769528_3839e84614.jpg?v=0

I hope you see how I could have missed that when thinking back on the old motor and looking at the new on. I should have looked at all the pics of the old motor before sitting in the "worry chair".... you learn something everyday! Enjoy the Albin motor pics... Thank you for all your help, I hope others can put it to good use, or I can if something drastic happens someday in the future!

Cheers!
Joel