hp rating

[1966starcraft18ft]

Got another question for you all, i see in literature that my 1966 starcraft holiday 18ft is rated for 120hp. Is that set in stone or is that flexiable???? The reason i ask is im a hot rodder at heart and would love to say i got a 300 hp boat. Just curious if i can upgrade my drivetrain or different boat.

 

[GA_Boater]

Re: hp rating

Sure you can say you have a 300HP boat. I mean you could put a 165/170 in a Holiday and be fine but not 180 HP over. If that's what you want, it would be best to look for another boat

 

[roscoe]

Re: hp rating

300 hp on that hull is not a good idea. The weight factor alone would turn me away from the idea.

You are going to need to change out the entire drive line.

I would likely look for a modern 3.0L 4 that puts out 130-140 hp.

 

[CheapboatKev]

Re: hp rating

Is this an OB or I/O?
For a OB I'd go to 150...
For a I/O, if you are running a 4 banger 120 I'd leave it alone.
The problem with I/Os is dollars spent versus increases in WOT speed is not the same as say putting 350 cubes into a vega wagon.
The payoff isn't there.
If I ever was to have had to reach my 120 in my Holiday, I would have looked for a 165 I6 motor.
That's as crazy as it would get.
There is also a bunch of insurance reasons were if you were to be involved in an accident on the water, being WAY OVER the hp limit

 

[64osby]

Re: hp rating

I didn't think they rated I/O boats, just the OB's.

With 300 HP you might as well replace all the rivets before you splash.

 

[GA_Boater]

Re: hp rating

I didn't think they rated I/O boats, just the OB's.

With 300 HP you might as well replace all the rivets before you splash.

And after! :lol:

I/Os are rated as well, 64. All the tags and specs in the brochures have max HP for I/Os.

 

[jbcurt00]

Re: hp rating

And after! :lol:

W/ 300hp on tap in an 18ft Holiday, I don't think there's gonna be much 'after'.....

Well, um, yeah, not much other then 'recovery'..........

 

[CheapboatKev]

Re: hp rating

Yep, for sure I/Os have max hp as well
My holiday I/Os data plate had max 140hp stamp.
It's all about hull strength and flex. Ya can't put 16 ounces in a 12 ounce can..lol

 

[GA_Boater]

Re: hp rating

But we always try to put ten pounds in a five pound bag.

 

[64osby]

Re: hp rating

On my Mariner the mfg plate states max hp for an outboard. Do I/O mfg plates have that rating?

Yes I see the brochures list a recommended hp for both.

 

[Gibbles]

Re: hp rating

If talking outboard...
I'm a big fan of allowing some flex in the HP raiting... but 300hp in a boat rated for 120hp... no way!

I have a Jet that's rated for 35hp or 45hp (I forget), and it has a 65hp on it + a 9.8hp kicker...

It works, but the back sits real low, and I have to weigh the front down to keep it from bobbing... :lol:

if it were me I would flex it out to maybe 200hp max (only a newer 2 stoke, and that's pushing it)... but I would go off of weights... like find out what the highest weighing 120hp engine weighed in 1966, and use that for your baisis, I would try and stay close... but allow some flex maybe +100/120lbs...

Just my 2 cents from my overpowered 15ft 1963 Jet... :watermelon:

 

[matt167]

Re: hp rating

Get the most HP you can without going heavier. Realisticly, your boat could have come with say a Mercury 1100 ( 110HP ) 6cyl Tower Of Power. You could pretty safely switch to a 1500 ( 150HP ) and be just fine given they weigh almost the same

 

[CheapboatKev]

Re: hp rating

Yes I/Os def have max hp

 

[Bob_VT]

Re: hp rating

300 hp would crush the hull from the banging and split the aluminum chines........ then you will have a 300hp submarine. You want 300 hp then you need a boat designed for it.

 

[matt167]

Re: hp rating

A Cheap 300hp boat is going to be an I/O... A Holiday 18 I/O with a mildly built marine 350 will be 300hp without much issue. It won't weigh but a few hundred extra pounds at the stern but would still float ok. I do think it would be overkill tho... A 470 Mercruiser with a decent aluminum cylinder head and the right pistons, it would probably make 250hp without much issue and be just as light as the little 2.5/3.0L Mercruiser. Given later Starcrafts used the 470 and 4.3L's in the same hulls, it's probably not far off base to use one of them in the older hulls as an upgrade.

 

[GA_Boater]

Re: hp rating

Well, the OP has a M/C 110. So it is an I/O. He also has a 1966, which does not have the added chine to rib gussets. So exactly like Bob-VT said, split chines are in his future if he gets carried away with much of any HP increase.

I say use it the way it is or buy a bragging rights boat. All my opinion, of course.

 

[1966starcraft18ft]

Re: hp rating

Ok. Got it. Hp rating pretty set in stone due to engineering of hull. I was just curious because like i said before, im a bit of a hot rodder and am always looki.g forcway to shove 20 lbs. in a 5 lb bag.

300 hp was just an example. 300 hp on a tbe water in a lil boat like my starcraft 18ft is dangerous in my opinion.

 

[1966starcraft18ft]

Re: hp rating

On more thing, can one of you fine gentlemen take a look at my fuel system plumbing thread and give me some opinions please. I really need to pin down my fuel system plan.

 

[1966starcraft18ft]

Re: hp rating

On more thing, can one of you fine gentlemen take a look at my fuel system plumbing thread and give me some opinions please. I really need to pin down my fuel system plan.

 

[grzzzz]

Re: hp rating

Hi again 66

Some of the lakes I fish here in the mountains of NM are higher than 8000ft. My 110hp really struggled. I made all (very minor) changes to get to the 120. Still couldn't plain. At these elevation I was only getting about 75hp. I put in the chevy straight 6cyl, it was an older one, had 150hp on the valve cover, dropped right in (had to extend the front motor mount about 6") and I am now very happy. With a couple buddy's, days liquid refreshments, coolers enough tackle to supply a Bass Pro shop, she'll now plain out at about 35mph, gps.

Grzzz
The Smoooooth!