HP rated at prop or Crankshaft on a chrysler ?

fucawi

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Noted a comment from Frank that the 105 was a 90 so the question...where did chrysler rate the engine power.?? Prop or crank ?..This is important to me as as I have a 30 HP but the boat (2011 model) is rated for 25 hp ...Its a 303H9C 1979
 

jerryjerry05

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Re: HP rated at prop or Crankshaft on a chrysler ?

If it says 30 hp it's too big even if it's really a 25 or 20.
What's in print is what the cops go by.
Remove the sticker!!J
 

JB

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Re: HP rated at prop or Crankshaft on a chrysler ?

What JJ said. Only making 25HP at the prop is not the same thing as being a 25. I think all Chryslers were rated at the crank.
 

Frank Acampora

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Re: HP rated at prop or Crankshaft on a chrysler ?

Prior to 1982 US outboard manufacturers rated their engines wherever they wanted to do so. Merc rated them at the prop while others rated them at the powerhead (higher horsepower sounds better for marketing and sales). In addition to this, Merc always under-rating their engines (in the early years) this was why Mercs usually outran other engines with the same HP rating. Think about it: a 100 HP Merc rated at the prop was actually delivering --let's say-- 110 while the Chrysler 100 rated at the powerhead was delivering about 85 at the prop. Which one would have been faster?

After 1982, at the urging of the association of outboard manufacturers--or whatever they are called-- all manufacturers started rating their engines at the prop. So true usable horsepower depends upon the year the engine was made.

However, as stated above, the gendarmes will use the decal or internal HP plate to determine if you are legal or not. As far as they are concerned, a 30 is a 30 is a 30.
 

huskerdaninva

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Re: HP rated at prop or Crankshaft on a chrysler ?

Interesting thread guys. My 1969 Chrysler Valiant 14' has the CG plate and she is rated for 55hp. However, I have all of the paperwork from the original sale in Ohio from back in the day and my boat came from the dealer with a 1969 70 hp outboard attached to the transom. Wonder how that came to be? My first thought was the powerhead may have been rated at 70hp but the rating at the prop would be right around 55 hp factoring in parasitic loss from the powerhead to the prop. Any thoughts??
 

Frank Acampora

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Re: HP rated at prop or Crankshaft on a chrysler ?

Dealer is in business to make money. If you insist on buying a larger engine than the capacity plate states and if he is a bit lax, do you think he will kill a sale or give you the larger engine?

Back in the late 60s there weren't nearly as many boats on the water and local enforcement was much more relaxed. For example: In New York (from where I originally came) there were no yearly tags. You registered the boat the first time and put on the numbers then every three years re-registered on the honor system. Didn't re-register? Who could tell from a distance? You had numbers. They needed to board and check your papers. ---Well, that changed in the '70s!

Back in the late '60s, you could do pretty much what you wanted.
 

fucawi

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Re: HP rated at prop or Crankshaft on a chrysler ?

Well frank the 18.5KW is moulded into the polyethelene....and we have no boat cops its all to do with your insurance ....So my boat is rated 2011 25 hp at the prop and the engine is rated 30 hp at the crank ..so no problem allowing for a 15-16% loss ...I could just put a 25 hp cowl on it or take the 30 hp plates off the cowl .... I dont think we will have a big problem here with 4 mph limit on most rivers and canals unless you are 300m from shore or in a ski zone,
I need the bigger output motor for the tidal rivers where the 5hp briggs and stratton would struggle
 

roscoe

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Re: HP rated at prop or Crankshaft on a chrysler ?

This topic has been covered hundreds of times.

The amount of hp loss from crank to shaft, about 5-8%.

30 is 30 if a 30 says 30.

Where in the world are you that you have a 4 mph speed limit, and how do you measure that?
gps? boat speed? land speed?

If you have a 4 mph tidal current and have to get back to port, you could never get there.
 

fucawi

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Re: HP rated at prop or Crankshaft on a chrysler ?

UK speed limit 4 mph sometimes 8 kph measured over the river bed .( over the river bed so gps) .originally imposed by the railway companies to stop river transport competing with the railways ...very boring Australia and US rule when it comes to fun on the water ...Jetski ..private water park ....you only quote your insurance no when getting your lisence ..trouble is different licence for different rivers nightmare and expensive ..I just pull out the one lisence I have and give them my australian driving lisence ...write to me in Mooloolabah ........Think I will re do the graphics on the 30 over the winter and make it a 25 ......and use modern garphics like the attachment (not my motor)
 

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WaveJumpingMaxum

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Re: HP rated at prop or Crankshaft on a chrysler ?

Thats crazy. 4mph? When I go 32-34 at wot its too slow. I actually have a similar issue cause I have a 89 Maxum same thing as a Bayliner, too much boat not enough engine. 17ft Bowrider only rated for 85 hp, seems like it should be a couple more ponies.
 

JB

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Re: HP rated at prop or Crankshaft on a chrysler ?

Please don't ask for, or offer, "permission" to violate law or manufacturer's specifications. That would definitely be unsuitable material for iboats forum.

If it says 30 on the cowl, tag or title it is a 30.
 

WaveJumpingMaxum

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Re: HP rated at prop or Crankshaft on a chrysler ?

Do outboard engines have any kind of mods you can bolt on? Like cars have diff air intakes and exhausts , is there anything similar for a boat engine all Ive found to increase speed is some article about squaring up the exhaust ports and or investing in a new prop, got a 14 pitch now pretty waffled up from the previous owner.
 

fucawi

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Re: HP rated at prop or Crankshaft on a chrysler ?

Well clearly you can improve on the makers design a little and there are many books on tuning the 2 stroke motor and many tricks like 2 % molybdonem in the oil. To check your prop run at WOT and read the rpm . should be in the range for your motor probably 4500 -5500 changing the pitch 2 inches changes the revs 400 .....you cannot go faster by fitting a higher pitch prop....you need to fit a bigger motor to do that !!!
 

WaveJumpingMaxum

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Re: HP rated at prop or Crankshaft on a chrysler ?

That was my orginal intention when buying the boat, hammer the force WOT till she blows up cause i got the boat, galvenized trailer and running engine all for 700 i took a 1day class to receive my boating/pwc liscense in the US some states let you take the test online Connecticut unfortunatly makes you site through a 8hr class, found out about the tickets for going over the hp then, but Ive even seen boats the same size , width , height only difference was the manufactur and it was 17ft instead of 16'8, and the boat was rated for a 150?!!? WOT now with my 14pitch prop i belive its 13in I place out at 32-34 @ 5500 rpms :/ not fast enough to catch my cousins 14ft larson with a beastly merc800& brand new prop.
 

Handyman1

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Re: HP rated at prop or Crankshaft on a chrysler ?

hi i am new to this forum so i just start it ease. The plate on the boat states on my boat the RECOMMENDED max hp not THE max hp
 

fucawi

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Re: HP rated at prop or Crankshaft on a chrysler ?

True but like I said its down to insurance and a 2011 boat will just have max hp plated on it
 

dbrojr

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Re: HP rated at prop or Crankshaft on a chrysler ?

my '89 maxum quantum 17' fish and ski w/ 85hp(max rated) does 46 on gps @5600 rpms.may be just different hull design and configuration.
 
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