*THE HULL TRUTH is the world's largest FREE network for the discussion of Boating & Fishing. Whether you're researching a new boat, or are a seasoned Captain, you'll find The Hull Truth Boating & Fishing Message Forum contains a wealth of information from Boaters and Sportfishermen around the world.
Welcome to the updated THT!
If you are having trouble signing in, please email feedback@thehulltruth.com with your username and we will help you. We thank you for your patience as we help you access the new site!
Random Quote: That which does not kill me really pisses me off...
I think I've finally settled on the model for my new boat, but a new question has entered the picture. I can save a good deal of money by going with a 20" transom height boat in stock verus ordering a 25" transom. However, the actual transom height is closer to 22". Another THT member is of the opinion that this situation has caused porpoising in his friends boat (which is the same model boat I'm considering). Is this the likely cause or is some other problem a more common cause of porpoising? If not, will the 22" transom with a 20" shaft OB create some other undesirable condition. I don't want to fight a problem after spending the money, especially if I can prevent it all together by spending the extra money on 25" transom and OB from the outset. Any input would be appreciated.
I did send an email to the manufacturer asking this question, but they did not answer the question directly and simply stated that this boat is offered in 20" and 25" transom heights.
It's a 17' center console boat, so rough (2'-3") water will be encountered only when unexpected or from poor planing. When you ask about rough water is it from the perspective of handling with the combination described or simply that the powerhead is closer to the water? Due to the design of the boat, water getting into the boat is not materially changed by the difference in transom heights.
For a 17ft boat, I would go with a 20 inch transom, not the 25inch. Even though they do make o/b less than 150hp in 25 inch shaft, it is not nearly as common as a the 20inch shaft. Check to see what hole the ob is munted on. This way you will can move it down if their is a problem which I doubt their will be. Also, I think that the 22 inches is normal for the 20inch shaft. I seem to recall that the 25 inch shaft motor transom can be as long as 27 inches. Unless it is a weird hull design, I would go with the 20 inch shaft without even looking at the boat due to its lenghth. Just my 2 cents
The shorter transom height will increase the chance for the boat to take waves over the stern .... this creates a very unsafe boating concern .... go 25" transom your only lookinh at what 10-20 dollare per month at the most ./..... Last thing you want is a boat thet you do not feel safe in and will not take it out to where the fish are due to water condition's ....good Luck ...John
I would say the same thing about the transom height but having read the third post, I read into it as just having the motor higher and not having the transom higher for both motor set ups?
Do the different transom heights reflect different hull designs (i.e. deeper-vee vs. modified vee)? That is **usually** the reason a hull is offered in two transom heights--the difference is not due to a higher "water-to-transom" measure but rather a deeper keel.
If the hulls are the same and the transom is indeed higher by only 3", and the boat is self-bailing, the taller transom is not going to be markedly safer. It is more an issue of getting your feet wet a little less often.
A downside to the taller transom is a slightly higher center of gravity since the powerhead is higher. Not a safety issue, but the boat might be marginally less stable at drift.
I agree that you should go with the 20" transom, unless the hulls are different and you will be spending quality time in nasty chop.
BTW, what boat model are we talking about? That might aid the discussion. :P
Its a Cape Horn 17. The hull is the same regardless of the transom height, and it has an enclosed splash well, which should eliminate transom height as an advantage in preventing water from reaching the deck.
Do you think the position of the prop relative to the hull bottom can or will be a problem and is porpoising a likely result?
Yes. Too short a shaft will cause porpoising. I made the mistake of mounting a long shaft on a deep v hydrasport many years ago. Not knowing that extra-long was what I needed, I could not get on plane effectively and had terrible porpoising. Sold the short motor and mounted the proper lenght shaft and the boat ran like a scalded dog.
As I have stated in my replies to Dodge's post, in regards to comments made by mbb.
I am not sure if he has a long shaft motor on a short transom or a short shaft on a tall transom but I think that the boat mentioned is not set up correctly. This is the root cause of the "pounding" not the boat. Also in his reply he is indicating that maybe the boat and motor came from different dealers, while this should not matter, often it does. You end up with a problem and the motor dealer says it is the boat, the boat dealer says it is the motor, you get the picture. Research the CH-17, mbb is the first case I have ever heard of where any pounding has been reported.
While researching my purchase of the CH-17, I visited the factory on Feb. 5, 2003, while there I was able to view a CH-17 in various stages of construction. One thing that I remember is all CH-17 start out life as 20" transom models, that is how they come from the mold. After removal from the mold a block is glassed on to the 25" models to raise the transom hieght. So for all practicle situations the 20" transom is as strong or stronger then the 25" transom. In this boat I think a 20" transom will be just fine as long as you are not powering with one of the heavier 4str. Matter of fact while at the factory I inquired about that exact situation , heavy engine on a short transom. The factory manager replied that it would not be a problem but the appearence would make the impession of being way down in the water.
Jimy, I am not sure where you are located but if you are any where around B.R. La. maybe we could get together and I could give you a ride and you could see for yourself.
[This message was edited by twentynine on 10-02-03 at 08:05 AM.]
I think he has a short shaft OB with the 20" transom. I'm not concerned about the transom strength, and I will not be using a four stroke (115hpYamaha 2-stroke). I must admit that mbb's input had me slightly concerned as the 20" transom CH17 is actually 22" (I measured one after mbb's post).
Is your transom height actually 27".
Thanks for the offer, and as a matter of fact, based on your location from the other thread, I live within three miles of you.
I will be picking up my 17 Cape Horn with a 20" transom & 20" 150 Johnson on Monday. As twentynine said, the 20" transom is stronger, and will also lower the profile of the powerhead, and lower the center of gravity. You don't have to worry so much about water coming over the transom as the splash well will drain it back overboard. twentynine, what is your transom height? Sounds like we need a get together soon.
I have a 25" transom and a 115hp 4str Yamaha.
This afternoon when I get home I will measure my transom and get back to you Jimy.
Dodge
Anytime, I work shift work so I am off during the week and on some weekends. Now getting yard leave from the "Boss" that's another story.
While shopping for my boat I visited Mid City and I don't have any complaints about the way I was treated. However, it seemed to me that they really didn't want to sell me a boat set up like I wanted. I wanted 4str power and the salesman, maybe named Gary (big ole corn fed boy) was pushing 2str Johnson. Don't have any problem with 2str or Johnson just wasn't what I wanted.
Bought mine from Boat City, Hammond kinda worried them till they sold me that boat for what I wanted to pay. Slightly more than your price, by a couple hundred. Only needed service one time and thier response was very good. So like I said in one of my previous post, it is six months later and I don't have any regrets at all. Just wish I had more time to use my boat.
Not necessarily specific to the Cape Horn 17, but is there a general “rule of thumb” on the relative height between the ventilation plate and the hull bottom?
Although some transoms are not exactly 20" or 25", keep in mind that you do not measure along the transom to the keel - transom height is the distance from the top straight down to an imaginary line coming out from the keel. The higher the transom angle, the longer the distance will be if measured along the transom. Simple geometry - and you thought you would never need it!
I received an email from Cape Horn, who connected my emails to this thread and he wanted to talk to me about this subject. He called me, explained their building process and answered several questions. If I was not 100% sold before, I am now. If this is any indication of their service, I’ll be a very satisfied customer.
Transom Height 
THT sponsor
