Over Powered?

[JasonJ]

Re: Over Powered?

I agree that the max horsepower rating shouldn't be exceeded, but it makes me wonder why a 19 foot boat has a 125 hp rating and my 16.5 foot trihull has a 140 hp rating. Granted, my structure was beefy, with six full length stringers. I have seen a few Bayliners apart, and their structure leaves a bit to be desired, and that may be why the hp rating is lower. My friend has a 19ft olympic with a 175 horse Merc on it, thats what it is rated for. There has to be something with the structure of your boat. It seems like Bayliners in general have lower max hp ratings than the competition of the same length and hull design. Like the others have said, the 125 will do fine if it is healthy and propped right. On a side note, I had a 1963 17 ft runabout that was rated for 90 hp, I had 85 hp on it, and I didn't dare try to turn it at full speed any more than mild direction changes. I turned hard once, and the back spun out. Thankfully it didn't catch and flip, but it just goes to show that even within the ratings things can happen, happen quick, and an unconscious body breaths poorly in water. Good luck getting the right motor and remember your life is worth more than a good day of waterskiing....

 

[SCO]

Re: Over Powered?

Wilken,<br />One reason for the lower ratings for outboard vs inboard must be the aft cg and transom cutout. Even though 19 feet, I bet the boat is lightweight, and maybe has narrow beam at transom. As an engineer, you could compare motor weights and see effects on transom displacement.If weights ok prop to get the typical power output for that motor at say 3500 rpm and just govern yourself to that as a max rpm, with full realization that you are illegal and uninsurable. For example, in my case, I dont want to go with a new replacemenr hp engine. My '73 135 hp is much lighter than anything I have seen on the market today. My boat already sits too low at the transom. A 4 stroke for me is out. To go 4 I will have to get an new hull or suffer from low power. Older Boston Whalers I heard would not perform with equivalent hp 4 strokes, and I heard the new Montak's have more beam at the transom specifically to handle 4 strokes.

 

[wilkin250r]

Re: Over Powered?

I was toying with the idea of replacing the floor in this boat. Perhaps I should, and find some way to reinforce the stringers and transom while I'm at it.

 

[Franki]

Re: Over Powered?

I have a question here..<br /><br />I have a 17 foot half cabin.. it has no OB rating as such, (in Australia its not necesssary)<br /><br />The V stops about 2 thirds of the way toward the back, so the transom is almost flat across the back.. (very slight shallow v.)<br /><br />Its also fairly narrow.. but it doesn't sit that low in the water, even with my 100HP old Johnny on it..<br /><br />Is the narrow transom/low HP rating because of the floatation issue alone? or are there other factors involved?<br /><br />From looking at the hull design, the profile my boat has in the water at plane, is much the same as many high powered OB or Jet Speedboats, how come they do not have the same HP restrictions???<br /><br />Before I put the 100 on it,, I checked the stringers condition, then put two massive Jarrah beams alongside each one, bolted every 6 inches with stainless bolts, running the entire length of the hull. and bolted the floor to them.<br /><br />My boat is a clinker style hull (good structual strength) and the thinest fiberglass I could find on the whole boat is 5mm (the cabin sides.) and the whole back of the boat and splashwell is designed to support the transom. I can sit on the back of my 100HP with my 120kg body and bounce, and there is no flex of the transom.. so I think its ok from a structual point of view. (also the 100 has the exact same weight as the 85HP that this boat must have been rated for (at least).<br /><br />I don't actually know if I am over powered or not.. I have yet to try WOT to find out.. but the transom width issue has me wondering..<br /><br />I am gonna try and get a bow tank and move the weight forward where i can anyway, so that should help also. most of where I fish has a 8mph limit anyway, so for that I could use my kicker, but I do like to do a bit of sking and trips to the islands every now and then, and for that I need some power.<br /><br />Can anyone give me some details on the relationship between transom width and power ratings and the floatation details involved?<br /><br />regards<br /><br />Franki

 

[wilkin250r]

Re: Over Powered?

Franki- I obviously cannot tell you the relationship between transom width and Hp rating, but in my search for information I've seen many 16' boats with 125hp ratings. Based on this, I don't see an initial problem with 100hp on your 17'.<br /><br />I far as I can tell, the HP rating comes from the ability to turn the wheel 180 degrees at full speed with the max rated engine without loss of control. If this is correct, it seems to me to have more to do with hull shape than size.

 

[SCO]

Re: Over Powered?

Saw your boat on the pics page Frank. The 135 on my 18 (really 17.5) is not too much power, but it does jump right out of the hole. As propped my wot is 5200 rpm at 42mph. I like to cruise at 30mph(about 3700rpm). I wouldnt think yours to be overpowered, boat looks heavy enough. I like the semi flat transom bottom. Mine has a deep v there and so a deep motor cutout, and deep draft. Yours starts floating the motor in just a little submersion, so I'm with you, weight not much of an issue. BTW, your motor looks like the same block that I have(v4). There is some info that was discussed maybe 10 or 12 months ago in a thread that referred to a US coast guard publication(on line I think) about how to determine the power rating for a homebuilt boat.

 

[SCO]

Re: Over Powered?

Check this link. <br /> http://www.iboats.com/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=003986 <br />It is a prior Iboats thread.

 

[ob1jeeper]

Re: Over Powered?

bushcat<br />If you were offended by my comments... so be it... it's a free society, so grow up...<br /><br />The beauty of being an engineer in the missle defense systems arena, is that you've obvoiusly never had to sit in a court room and be accused of gross negligence, which resulted in the deaths of poor innocent consumers, (never mind they happen to have WELL over the legal limit of alcohol PLUS significant amounts of mind-altering drugs found in thier bodies during autopsy).<br /><br />The worst part, is when these accidents involve children, unable to get out of harms way, and who are unable to protect themselves from the irresponsible actions of so-called "adults" (they can be engineers, politicians, beauty shop operators, or farmers... doesn't matter... We seem to breed a fresh crop of them on a regular basis...)<br /><br />If you want to talk about making modifications to enable you to compete in racing venues, then all bets are off, and any modifications you discuss are "ok"... as you SHOULD be mature enough to understand the possible consequences of your actions, and you will be greatly reducing the potential risks to unsuspecting "civilians".<br /><br />HOWEVER, if you want to discuss using that same machine to operate amongst the "civilian" populace on "civilian" waterways... (IE: those who are totally unsuspecting members of society, who have the potential to be harmed by your actions), THAT's when I take issue with your vocalized line of thinking that says it's "ok" to advise folks to do so "because I got by with it, and I'm and ENGINEER, so... I can ONLY give good advice !!".<br /><br />If you've been an engineer as long as you say, you SHOULD be able to admit that not ALL engineers are created equal. AND, just because you have an ME degree, and have worked in the defense industry for 23 years, does NOT translate into your being able to give sound advise, regarding the boating recreational industry.<br /><br />As far as who's daddy is bigger than whose, and the fact that you think just because you built a couple of "Jeeps" that could tear mine in half, ALSO does not translate into your being able to give sound advise regarding recreational boating safety.<br /><br />There is no need to brag about accomplishments, or degrees to share the advise requested, and which has been provided. I happen to agree with the majority of folks who've posted, that doing this sort of thing in the recreational boating world is irresponsible.<br /><br />You have an ME degree... duly noted... But that does NOT impress me in light of the "advice" you've shared...<br /><br />So you have a couple of Big-Bad "Jeeps"... duly noted I am STILL not impressed...<br /><br />SO... now you have a Chevy that will eat ob's car's lunch... STILL not impressed...<br /><br />Next thing we know, you will be telling us about the the time you set off a JATO rocket, attached to the back of your 66 Chevy Convertible, on abandonded railroad tracks leading into a mineshaft in New Mexico... NOW THAT would be impressive !!! AND, of course right on track with the "my daddy can beat up your daddy mentality"...<br /><br />Nuff said on this topic already... let's get back to boating... hopefully with a modicom of common sense when we operate in "civilian" waters...<br /><br />Obiwan Jeeper

 

[G DANE]

Re: Over Powered?

To Franki100ESL72<br /><br />Hi Franki - I enjoyed reading your posts. I have a boat too with no rating plate, and going to fit it with my newly bought 115 HP evin. ( No restrictions here in DK, everything you doo just have to be "Safe ? ". I went to the US Coast Guard site, you should do too, search for "Safety standards for backyars boat builders" They have a good complicated formula of calculating horsepower ratings, considering mesures,chine,weight a.s.o.. I did this calculation and got out at 105 HP, so I guess I will be OK with this 1991 115 and 10 HP´s of common sence in between !!

 

[SCO]

Re: Over Powered?

Thanks from me also Gdane. THats what I was looking for and downloaded. Here's the link.<br /> http://www.uscg.mil/d8/mso/louisville/download.htm

 

[Kenny Bush]

Re: Over Powered?

Wilky, I apologize for Ob1jeep chewing up airspace on your topic. It seems he is upset that I am "making you" overpower your boat. Well here in America, we can openly debate issues and we have debated this topic, and had some excellent information given. Now it is up to the individual to accept or reject the data given, and implement whats learned. Some people get a little caught up in judging, or policing the world. I just get as much information as I can, and make best educated decisions to overcome my problems. I have repeatedly solved my "underpowered" problems, and I am still living and breathing to tell about it(I am a good christian). Besides, if I do put a rocket on a rail and shoot myself to the moon, let me go...My grandpa says it is the "Natural selection process"....Thin the herd he says...........Well anyway wilkin, good luck.....Heck even I learned a bunch from all the deliberation..Thats what this board is for.....Goodluck..BushCat<br /><br />Hey Ob1jee*****, I think you should put sidwinder missles on your boat for added horsepower......Oh my god, I bet you are twitching after I ordered you to do it.....Oh yeah, its just advice that you are going to sue me over............