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Mercury Short or Long Shaft?

kaydano

kaydano

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Some of you know I'm looking to trade up my Mercury 115 to a Mercury 150. I'm getting very close. When calling around, I was asked whether I had the short or long shaft, and I really don't know. Is there an easy way to tell?
 
By measuring the exhaust housing, between the powerhead, and where the gearcase bolts on. A shortshaft engine will have an exhaust housing length of approximately 15 in. The longshaft engine will measure 20 in.
 
Thanks for the quick response Jim. My boat is not at the house to take a quick measurement right now....

Does anyone know if MOST Mercury motors on Benningtons are either one length or the other, usually? When we ordered the boat, we got the default, as I don't remember specifying either. My dealer took care of that, and I don't know what he ordered. I am not doing the current trade with my original dealer. Going with someone local instead of 2 hours away.

Maybe my real question is do the new 150s come in both sizes? If they don't, then I don't really need to know since there won't be a choice. What I have now would be irrelevant in that case, as they are gonna get my trade-in regardless of what it is.
 
I just found the brochure, and the new 150 comes in both 20 and 25 inch lengths.

Is the rule that the shaft length should match the transom height?
 
I keep answering my own questions. On "build a boat" it looks like the 20 inch transom is always matched with the 20 inch motor. The 25 always goes with the 25. So I get that now.

But what's the difference? Derrick, I know one transom is 20 inches and the other is 25! But why would you want one over the other? Does it have to do with how the boat sits in the water or how heavy it is? I thought that's what the different mounting holes were there to adjust for...

From build a boat, it doesn't appear like there's a recommended transom height for the 24 SSL. From what it appears, they leave it up to you to decide which you want. How do you know which to pick?
 
I always say I have a bigger shaft; it just sounds better.
 
I was waiting on someone to jump on the comments ....... LOL !!!!
 
Would a 20" be for two tube and 25" be for 3 tube to get it lower than center tube ???
 
I was thinking about things along those lines, weight, buoyancy, etc. But you would think "build a boat" would specify/recommend one or the other based on the hull you selected. I don't know. Good thought.
 
The build a boat just gives you the option because they have no idea what motor you are putting on. Maybe you're on a restricted lake with only 20hp and it only comes in a 20". I'm not saying that's the case, but they don't know. By offering both it opens the market to anything. As for what is better for what. I don't think there is a difference. The motor ends up sitting at the same height regardless. At least that's the way I see it. If you have a 20" then they reduce the transom height to get into clean water, if you have the 25" then they leave it alone and it is in clean water.
 
I guess that makes sense. If one transom size was better than the other for a given model and hull, I suppose Bennington would have recommended the better one.

So, is the bottom of the two transom sizes at the same position in the water? In other words, with two identical boats sitting on identical trailers, would both transoms be the same height off the ground (as measured from the bottom of transom to the ground)? That would put the top edge of the transoms at different heights, one 5 inches higher than the other? If that's how this works, that would put the prop shaft at the exact same depth either way (20" transom and 20" motor vs 25" transom and 25" motor).

Sorry for pressing hard on this, just hoping someone chimes in before I make a deal on the wrong motor size tomorrow! It might have been quicker for me to have just taken the hour round trip down to the boat and back to measure it like Jim suggested at the top of the thread. Maybe I'll run down there early in the morning before work and take some measurements, then call the dealer and make sure he has the right one for me.
 
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You can just call the Mercury warranty number and they can tell you the model number and shaft length, assuming your dealer registered you.
 
does this help?
 
Jared - That does help a lot. Looks like transom height is just personal preference. Or if you already have a motor, Bennington will install the correct transom to fit it. TB's comment said performance differences are very slight between the two, so I guess that gets to the bottom of it. Thanks for digging that up.

TomS!!! Great idea! You saved me an early morning and an hour round trip to the boat. And I may not have taken the right measurement anyway since I don't really know what to measure, other than what Jim said to do. I spoke with Mercury about something a year ago or so, and they do have my motor registered. I'll call them tomorrow. Great idea - Thanks again!
 
TomS - Took me all of 1 minute to call the warranty hotline and find out I have the 20" shaft. Thanks for the idea.
 
kaydano said:
TomS - Took me all of 1 minute to call the warranty hotline and find out I have the 20" shaft. Thanks for the idea.
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You're welcome!
 
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