Outboard on full transom

[Gerardi]

I have a 21 foot open console boat that originally came with an inboard. I removed the engine and would like to fit an outboard. The boat has a strong full transom (no notch, no motor well) which I would like to keep. The transom is 33 inches high. I have no outboard yet and would not mind getting a 30 inch shaft motor, however this would still leave me a couple of inches short. I am thinking of a hydraulic jackplate. My question is this - what can be the least setback jackplate I can use to be able to lift the motor (probably a Yamaha 225 or 250) so that it can then be tilted over the transom? Basically I would not like to move the outboard too far back from the transom for aesthetic reasons so I would rather work with a six inch setback than a ten inch one.


Is there any source I may check to see the curve (?) the lowest (transom side) part of the power head makes as it is tilted?

 

[99yam40]

Re: Outboard on full transom

I would think if you have to run it lower than the transom, you would have to raise it up even or above the transom to be able to tilt the motor without hitting. Just my thoughts, as I have not seen this done before.

 

[mommicked]

Re: Outboard on full transom

What about a bracket? I hear they make all boats handle or ride better in rough water and tilting would not be a problem at all.

 

[CaptainKickback]

Re: Outboard on full transom

It doesn't seem your dimensions are going to work well. I am converting to OBs and have reaserched the brackets. Even visited sever of tye compaies that make them.

The reason they set back the amount they do (26 to 30") is so the OB can be tited up. There are a ton of benefits to a bracket, but you'll have to get over you asthetic preference.

BTW, I'm going with Armstrong. A bit more expensive, but was very impressed with their design and their operation when i visited them.

 

[Larry Tate]

Re: Outboard on full transom

if u dont want to tear that transom up, its gonna have to be pretty far back. lots of benefits from that, but i also do not like the look of it.

 

[Gerardi]

Re: Outboard on full transom

I am new to boating and this is my first project. Definitely taking in what is being written but where am I getting it wrong?

If the transom is 33 inches that should mean that if the jackplate is mounted 3 inches below the top of the transom, at its lowest point, a 30 inch shaft outboard should have the antiventilation plate just around where it should be, level with the lowest point of the transom. Now suppose I do go for a 10 inch setback hydraulic jackplate that can lift the motor 6 inches that is 3 inches above the transom. Would a minimum of 3 inches above the transom and 10 inches setback still not allow the motor to tilt?

 

[Turbojoe78]

Re: Outboard on full transom

I have a bracket on the back of my boat at least 24" (I never measured it) and have a 98 Suzuki 225 mounted on it. When I tilt the motor all the way up the cover comes within an inch of the back of the boat. (full height transom) So I'm going to guess that it's moving the motor cover at least 12" forward.

 

[AGENT 37]

Re: Outboard on full transom

If you get a six inch lift that takes the outboard a minimum of 3 inches above the transom and 10 inches setback it should allow the motor to tilt just fine. Another thing you might want to confirm is clearance required for the steering cylinder is sufficient. I'd assume that it is.

One thing to consider is the framing/support incorporated into the transom of the boat..... it sounds like you will be mounting an outboard high on the transom of a boat not designed for an outboard. You need to ensure that there is enough support for the outboard before mounting it on there.

Just curious, what type of boat and what size of an outboard are we talking about here? I'd likely opt for a full-width offshore bracket if it were me.

I've been in the position of having to make a taller transom work with a shorter shaft motor. In the end, I converted it from a 20 inch shaft to a 25. Unfortunately, you are not in the position to be able to make your shaft any longer.

 

[Gerardi]

Re: Outboard on full transom

The boat is locally (Malta) built. It is a 20 foot (7 foot beam) centre console with a full nearly 33 inch transom (originally had a Mercruiser Z drive 140 hp). It is a sturdy boat specifically built for a diving school aimed to take six to eight divers and kit.The transom had no rot and is nearly three inches thick. I have further strengthened it with mat going round the corners for about 3 feet on the sides. I do not feel there should be a problem there.

I acknowledge the option of a bracket however I feel that a two foot bracket plus an outboard attached to it would ultimately look/be rather too much on a boat that is only 20 foot.

I am thinking a 30 inch shaft outboard would be close to the height of the transom. I thought that if it could be mounted on a hydraulic jackplate which itself is mounted about 2 inches below the top of the transom the ventilation plate would be just about right. I was hoping that the lift of the jackplate and the setback would make it possible to tilt the motor out of the water. I am aware that the 30 inch shaft would mean I have to have a 225 hp (since smaller motors do not seem to come in such long shafts). My homework so far has shown that the current Yamaha or Suzuki four strokes in that hp range are still lighter than the original stern drive the boat had (while acknowledging that the outboard would be sitting further but not too far back). My experience with the boat as it was originally powered is that the 140 hp it had was just enough to reach 30 knots. I feel the extra hp will not really be that bad on the boat. Such a motor might also have the added benefit of keeping the motor head away from the water (???)

The problem here in Malta is that both platforms and jackplates are rare to see on boats (around here there are sterndrives, inboards or outboards on notched transoms) so one cannot go to a marine to ask or observe - it's all rather anecdotal - so I really have to tread cautiously given I am totally new to boating.

Thanks for your help

 

[giericd]

Re: Outboard on full transom

doesn't sound like you are going to get enough clearance with out a bracket. even if you went with a 12" hydrolic jack plate which usually isn't recomended with out serious upgrades to your transom due to the extra stress it causes on it, you still run in to the problem of only being able to tilt so much. I guess it could be do able though. measure 10"-12" out from your transom and hold a broom stick verticle at that distance(10-12"), then take another and position the top of that one where the top front edge of you engine would be and pivot stick #2 untill it is about 2" from touching the transom. as you are doing this have some one stand on the side of the boat and look to see at it's max tilt if the skeg would clear the bottom of the boat, you don't want it below the lowest part of the boat. Another way to look at it is that when you trim your motor when you are running the engine only moves may be 4" if you have enough clearance to trim it that much and your jack plate will lift your motor high enough that the bottom part of the enging is above the bottom of the boat it could work. I just see some serious issues with over tilting the motor unless you find a way to install a cut off for your tilt to prevent over tilting. go with a bracket!!

 

[mobilemike]

Re: Outboard on full transom

Any yamaha dealer should have the factory manuals on what ever engine that you are thinking about.In the front of the book is a section on rigging info and engine dimensions,including full tilt and degrees of turn.Yamaha also has a good website but does not list that info. I'm sure if you contact them through that site they will provide you with the technical drawing in the manual. I've seen what you are trying do do,but i don't think that it will work in your case with just a 6" set back.Another thing to consider is that for every 12" of set back you can raise the engine 1"(rule of thumb). I'm with everyone else on this,a bracket is the way to go.It will spread the load over a wider area of a transom not designed for an outboard and allow you to keep your full transom.Stainless marine has single ones starting at $1000. Good luck

 

[Home Cookin']

Re: Outboard on full transom

Brackets go well on center console boats. You can start a new trend; have lots of pictures handy from boats in the USA rigged that way (be sure there are girls in bikinis, too).

I was just on a friend's 21' proline, center console. She added a bracket for her 150 Yam 4 stroke. Gave it a nice auxillary platform off the stern, which would be handy for diving and fishing. Boat ran really nice in extremely shallow and narrow creeks in the marsh, and she takes it into the ocean often, as well as across rough open bays.

I think a jack plate AND a bracket is too much going on back there. You don't want to have to operate both just to raise the motor.