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| Anyone do it? One fellow today at a dealer said it could be done. Would the motor mounting screws still hit the boat transom? depth of the mounting bracket is needed i guess. Is it safe? Thanks. |
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Posts: 332
Location: Michigan | Bruce,
The cavatation plate on the shaft of the outboard should be even with the bottom of the hull when the outboard is mounted. In general short shafts are made for 15" transoms and long shaft outboards are for 20" transoms.
Jay |
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| I know that. I was wondering if anyone has 'built up' a transom so a long shaft can be used on a short boat. The Honda in town is a long shafted motor, while the boat I want to get has a 16" transom. |
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Posts: 332
Location: Michigan | Sorry for not understanding your question. I know guys that have added jack plates. One friend ended up having a bad (cracked) transom from the extra torque. |
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| You're saying it was caused by the plate?? I went to the dealer today and saw the boat. He showed me the plates too. A larger Lund was using them to hang a kicker on. This dealer wants $176 for a pair installed. It's a 16' Naden that I will put a 15 4-stroke Honda on. Motor is 101 lbs. Boat will take a 35 HP max. I think I will hang it myself w/o those plates. I mean nothing of that motor is touching the boat!! I will lock it to the transom as well as bolt it thru the alum skin and the wood under that. At least my insurance man will be happy.  |
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Posts: 3508
Location: Elk River, Minnesota | You can mount a 20 inch shaft on a 16" transom, but with a 4 stroke, there is a major word of caution in doing so...
First and foremost, when the powerhead and oil reservoir is closer to the water, you run more risk of water intrusion to main engine block, which will ultimately end the life of the motor. This is why many of the larger boats out there are now going with a 25" transom as compared to the popular 20" and from years ago, the 15"
Secondly, make sure that the boat has been constructed with 4 stroke engines in mind. I am not sure about Nadens, but many boat manufacturers have added extra floatation in the rear of the boat in order to pass USCG requirements for level floatation in the event of swamping the boat.
Now..in your case with a 100 pound motor, floatation may not be an issue, but I can tell you this...mounting a 20" shaft motor on a 16" transom will be very lethargic on getting the boat up on plane, and will be more apt to hit underwater objects since the shaft is 4 inches lower in the water. The more lower unit in the water, the slower and more inefficient the motor will be...you will use more gas in order to run the boat because of the excess drag of the extra 4" of lower unit in the water.
Now..there are options, though, too. Many marine dealers will carry some sort of plate that will allow you to run a 20" shaft motor on a short shaft transom. They range from having a set-back of 4 inches or so from the transom, to no setback at all...esentially raising the motor straight up off the transom. For a Naden, my suggestion would be a plate to mount the motor straight up off the transom. Then, add wave wackers to help keep excess water at bay in the rear in the case you are backtrolling in some wind, or running with following seas.
Even though you are running a small boat with a small HP motor, I wouldn't be surprised if the rear of the boat "squats" a bit due to the extra weight of the 4 stroke. a 35 hp 2 stroke weighs about the same, though too...
Good luck with your choices.
Steve |
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| In my last post I meant that I would hang the motor with a setup of my own, raising the motor 3 to 4 inches. Thanks for the tips though. My 1st thought was the prop hitting bottom if the motor wasn't higher. It will be locked to and bolted through the transom too. |
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| Where do you find wave wackers at? I have a small Minkota that I would like to put back there too. Slot in the wave wackers??? |
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Posts: 3508
Location: Elk River, Minnesota | I'd check with any marine dealer for those...they should carry them and I believe you can get them made to deal with a Minnkota as well.
Steve |
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| Looks like I am going to get the 2006 15 Honda short shaft ordered. Save me the headaches of trying to brace the other motor, somehow. Thanks for the help. The dealer put this Naden which only weighs appro 310 lbs on this massive Lund trailer. One local dealer says a 1000 lb trailer is too heavy for that boat. This thing is even heavier than that, 1200 lbs if i remember right. The boat will be held down with 2 straps on the transom and at the bow eye. Can a trailer damage a boat? by being too rigid? Thanks, the rookie. |
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Posts: 3508
Location: Elk River, Minnesota | I always go heavy on a trailer just in case you end up loading the boat up for a trip.
If the trailer is fitted to the boat correctly, you should not have damage occurr. I have seen damage on a friend's boat. The trailer never fit the boat too well (too wide of a trailer) and the boat always sat on the rollers cock-eyed. Due to this, the rollers were not supporting the boat on the boat's stringers, and the roller pushed through the aluminum.
If the boat only weighs 310 (as they say) and the motor is 100, a 1200lb trailer would be the weight rating of trailer I would want.. Better to have extra than not enough..
Steve |
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