HP rating question

[rsimmons42]

I have a 1989 sunbird SPL155 that is rated for 70hp, I had a johnson 70hp on it but the motor was/still is giving alot of trouble. I have purchased a new engine that is on its way it is a 75hp. I purchased a 2008 75hp Optimax. The floor was just replaced in the boat and everything was inspected at that time. The Transon is 2 1/2 inches thick and very solid.

Is hp rating mainly for the design of the boat? Is it mainly for the sturdeness of the transom? or what determines it.

After asking all of this I want everyone's opinion as to weather this is OK or not. I am a stickler for safety and want to insure that at any given time people in and outside of my boat are safe.

Please advise me.

 

[Bob_VT]

Re: HP rating question

Well unofficially you should be okay..... officially if there is ever a problem you can be found liable or insurance could refuse you.

It is a HP rating/certification based on the USCG standards and as far as I know it has been discussed here thousands of times. There are rumors that you will/could get a ticket in certain areas...... it is a sticky subject.

In my unofficial opinion the small 5 hp more at the prop should not kill your boat

 

[rsimmons42]

Re: HP rating question

would anyone else like to give me their input on this?

Thanks

 

[Tacklewasher]

Re: HP rating question

What VT said.

You are less than 10% overpowered. I doubt you would get a ticket anywhere and I'm sure the boat can handle that small an increase.

 

[solar7647]

Re: HP rating question

In my opinion the boat it self should be just safe as with a 70hp, but as Bob vt said you could runinto issues with any inspections and maybe insurence. Speak with your local water craft officer, they should be able to give you the best answer, and may be able to provide a way to get the Hp rating changed. Good luck

 

[NSBCraig]

Re: HP rating question

Sure do you think there is a reason that it would be unsafe?

I mean do you know it's unsafe and your just looking for someone to say it's o.k.?

If so than no don't do it, but if you don't know it's unsafe for some reason like the boat was already scary or is the boat not in good shape than don't sweat 5hp.

My friend just loves his 115 hp optimax they are great performing motors.

 

[rsimmons42]

Re: HP rating question

thanks guys,

I really appreciate the information, the boat is a project of mine that I take very much pride in, This is my first boat, the boat handled extremely well with the 70 johnson when it was running well.

here is a photo of the boat

 

[180shabah]

Re: HP rating question

the formulas for figuring hp ratings only account for transom dimensions, width and height to the lowest point. They are set for stability. More hp = more weight on the stern, usually. Do you know the weights fo your two engines?

FWIW - you will be getting more than a 5hp bump old engine was rated at the crank, the new one will be rated at the prop. I think you will like the difference. You should get easier starting, better economy and higher top speed. It's a win-win-win situation.

After all of that, I say mount it, install the controls and go boating.

 

[Tim Frank]

Re: HP rating question

Ran a 55 HP on a boat rated at 50HP max.for a number of years It was as good a match as I have ever seen.
I would not worry one minute about any safety issues, but you should check the legal and liability issues. I would suspect that there might even be a mechanism where you can get the boat re-rated.

Just noticed this is exactly what solar said.
Still, solar had such an insightful post it is worth duplicating....

 

[chrishayes]

Re: HP rating question

how would one have it "re-certified"? Seems odd that this could be done on any old boat.

 

[Willyclay]

Re: HP rating question

Here's a link to the USCG regs on calculating "maximum" horsepower capacity:

http://edocket.access.gpo.gov/cfr_2004/julqtr/pdf/33cfr183.53.pdf

Work through the correct formula for your boat and see what the number is. If it is higher than 70, then it would seem like the manufacturer, with the help of their corporate attorneys, installed a capacity plate that rated your boat at less than the maximum horsepower capacity allowed by the USCG. It's all about being safe. Good luck!