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Author Topic: AS 170 engine rating  (Read 1479 times)

October 12, 2016, 09:45:29 AM
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Surfcandy234

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AS 170 engine rating
« on: October 12, 2016, 09:45:29 AM »
hi

i have a 1974 AS 170 CC and i heard it was rated up to a 130 then i heard it was rated for a 115 then a 85, which one should i go by? i was thinking on putting either a 90 or a 115 on it
thanks

October 12, 2016, 12:25:57 PM
Reply #1

Capt. Bob

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Re: AS 170 engine rating
« Reply #1 on: October 12, 2016, 12:25:57 PM »
1975 model rated at 130 hp. I'm guessing 74 was no different.

]
Capt. Bob
1991 210 Walkaround
2018 Yamaha 150 4 Stroke
"Reef or Madness IV"

October 12, 2016, 07:10:43 PM
Reply #2

wingtime

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Re: AS 170 engine rating
« Reply #2 on: October 12, 2016, 07:10:43 PM »
Keep in mind your comparing apples and oranges. Back then outboard hp was calculated differently and it was rated at the crankshaft not the prop. So a what was considered a 140hp back then MIGHT be equivalent to a 115 hp rated motor today.
1998 Explorer w/ Etec 250


1987 170 w/ Evinrude 90

November 14, 2016, 07:22:47 PM
Reply #3

boatnamesue

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  • Jason
Re: AS 170 engine rating
« Reply #3 on: November 14, 2016, 07:22:47 PM »
If your question pertains to the legal rating for the hull, then it's 130hp.  The USCG requires boat manufacturers to list max hp on boats 20ft or less, purely for boater safety.  However, most boaters believe this rating is stipulated by the manufacturer so to not exceed the integrity of the transom.  This is not true.  HP for boats 20' and less are governed by the USCG.  The USCG law code is here, which includes the formula:  https://www.gpo.gov/fdsys/pkg/CFR-2002-title33-vol2/xml/CFR-2002-title33-vol2-sec183-53.xml

Using the max hp rating formula, you'll be surprised to learn the actually rating for your boat is 150hp!  A common procedure for boat manufacturers is to rate the boat for less than what the max hp the USCG would allow using the formula.  The reason being boater safety, thus reducing the manufacturers risk of lawsuit.

Using Yamaha as an example, the dry weight difference between the 115hp/130hp and the 90hp is 100lbs.  No weight difference between the 115 and 130.  Which now brings me back to your question: which rating do I go by?  The rating produced by the manufacturer, which is 130hp. 

I have a Yamaha 2 stroke 115hp on my '76 170.  My guess is the original designer of this hull intended the mounted motor dry weight to be less than 300lbs.  Either that or engines 40 years ago were lighter per hp.  The reason I state this is because when the boat is submerged at rest, the water line is above the location of the scuppers, regardless of the amount of fuel in the tank or any other weight factors.  Since the hull is designed "self-bailing", technically the scuppers should be above the water line.  No biggie, I just plug them when heading out.

Deciding on a 90hp, 115hp, or 130hp rests on 2 factors for you: your budget and how you intend to use the boat.

---------------
Jason
1976 AS 170
1998 S115TLRW

November 15, 2016, 11:25:03 AM
Reply #4

wingtime

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Re: AS 170 engine rating
« Reply #4 on: November 15, 2016, 11:25:03 AM »
Another limit on how much HP you can put on a boat is imposed by the insurance companies.  Hang 150 hp on the back of a 170 and I'll bet your insurance will go up.  Of course if you don't carry insurance than no big deal.

I have a 90 HP two stroke 60 degree Ocean Pro and I think it is a perfect power match.  That motor has a ton of torque.  If you nail the throttle without a good hold on the wheel you'd be in trouble.  So much so when my steering cable went bad I upgraded to a no feed back helm.
1998 Explorer w/ Etec 250


1987 170 w/ Evinrude 90

 


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