Engine size question

[rdzat]

I own a 17' early 70s semi V Cheetah with a 115 h/p mercury outboard, the boat is in excellant cond. the previous owner had the transom rebuilt because i'm guessing it had some rot, from what he tells me it had a 2x4 stiffener, he had them glass in a 2x6 stiffener during rebuild.<br /> Now my question is since I cannot find any i.d. tags on the hull how do i know what the max. rating engine size I can use? I have a chance to pick up a late model 200 h/p merc. at a good price, I feel the beefier transom should handle it but what about weight or other problems i might incur.

 

[JB]

Re: Engine size question

Is this your first death wish, Ron, or do they happen regularly? OJ The question of formulas for calculating max safe HP and load has come up in another thread in the past couple of days. There is a link to the site for the correct formula.<br /><br />Red sky at night. . .<br />JB

 

[kev_79]

Re: Engine size question

somebody else posted something similar earlier and someone else referred them to this:web page. It gives you the formulas to find your hp rating and capacity. I don't remember the post though. BTW the hp rating is very important. If you overpower, you could have trouble getting insurance, and put yourself in danger. Most boats can hold a much heavier engine on the transom, but they will sit the stern down too low in the water. Too much power can make a really light boat flip when it catches wind. We all love power, but stay within reason if your gonna carry anybody at all. Good Luck

 

[rdzat]

Re: Engine size question

I guess you pretty much answered my question maybe it would be to much for it, the boat runs about 45mph with the 115 guess i should be happy with that, I just hate to turn down the deal on the larger motor. Thanks for the response.

 

[JB]

Re: Engine size question

A hearty AMEN to Kev_79's comments. <br /><br />About 30 years ago a good friend and fishing buddy lost his 17 year old son when his 14' semi-vee flipped over on him when he was going duck hunting. Rated for 20, he had 40hp on it. <br /><br />Somehow he went to WOT as he came up another boat's wake and it just ran out from under him and came down on top. PFD didn't help with his head crushed. <br /><br />Some folks wonder why I am such a pain in the butt about overpowering. David ***** Jr. is why.<br /><br />Red sky at night. . .<br />JB

 

[what200]

Re: Engine size question

I checked out the coast guard page with the formulas but it wasn't working out for me...<br />For my 17'2" (68" across)blue fin alum boat it worked out to be 105 max hp- the plate says 100 hp- pretty close.<br />But for the 16' skeeter (80" across) I come up with 125 with the formula but the plate says 150 hp. So something isn't making sense to me. How can a 20' bullet be allowed to have a 225 without being almost 8 feet wide. Also, I would think that weight would be a part of the formula, I mean you can build a bass missle that an extra 2' on the nose that is never intended to be a functional part of the boat just to increase the hp rating. I could put 50lbs of sandbags in the front of my boat and accomplish the same thing.<br />I'm not trying to be critical of JB (especially since he is the best thing that has happened to this board). My irritation lies with the officials of alabama that decided you should get a ticket if you overpower your boat ANY. I understand trying to get the rednecks with a 3.0 merc on a bass tracker off the water. But I'm in the same trouble if I put a 115hp merc six on my 100 hp alum boat even though it probably only really puts out a 100hp at the prop.<br />I guess what my long winged point is I think hp rating should be used at guideline. This formula has a lot of grey area influenced by factors that are not accounted for. Should I stick a merc v6 on the back of my blue fin-No. But I see no problem with a 115 and a little extra weight up front.<br />Thanks to all for putting up with my B* itching.

 

[kev_79]

Re: Engine size question

I have yet to look at the formula, but I will try it out on my boats when I get a chance to check. Personally, I can't find much rhyme or reason at just looking at a boat an accurately telling what hp it could hold. I'll get back to ya

 

[Navigator]

Re: Engine size question

Remember, the formulas used are for most boats and are a guideline for the "Home Boat Builder". Different boats can handle different horsepower due to Hull design, chines, steps, rockers, etc... Also playing into this is the construction of the boat, ie: placement of the stringers, number of stringers and additional reinforcement. Another factor is the position of the operator. For example, I have a 16.5' Crestliner Welded aluminum Modified "V" Jonboat with a tiller. The boat is rated for a 35 hp engine. The exact same boat with the console is rated at 60hp. The hull is identical, but now the weight shifts forward. It really all depends on the setup.<br /><br />what200, <br />My brother had the same problem as you where he had a 90 on a boat rated for 85 and got in trouble. On his setup, he had modified the front deck of the boat so the weight distribution changed and the 90 worked really good. What he did was simply apply new decals to the cowl so he was compliant. Now please dont flame me. I dont agree with this practice. I'm like JB, a safety nut, but I just wanted to share what other people have done. <br /><br />Nav

 

[Cwr]

Re: Engine size question

Sometimes the rating on a boat has to do with the Coast Guard flotation testing they do. The reason I say this it they just tested a certain brand of aluminum boat that was rated for a 90 horse, but didn't pass the flotation test with the 90 so they rated it back to a 75. At least that is what the dealer has told me.