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Am i making a mistake

J

jd_singletary

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"Do you guys think i am making

"Do you guys think i am making a mistake replacing my raw water cooled small blocks with fresh water cooled big blocks? One of the small blocks was seized,the other one pretty much worn out.I know the big blocks will physically fitand i am sure they are quite a bit heavier.I gave this all some thought before i bought the engines and decided that the extra weight should not affect the boat all that much after all the boat can sleep six so i know it was designed to carry at least that many people.most of the time it will only be my wife and i on the boat so i figured thats at least six hundred pounds i wont be carrying so i can put in heavier more powerful engines.Well i get to the boat yard this weekend to put my new gas tanks in and I have a new neighbor,we get to talking,let me re-phrase that,HE got to talking and says i am going to ruin the characteristics of the boat putting those heavy engines in there.I think the guy just likes to hear himself talk.I wuold really like to hear what you guys think. thanks jody"
 
"[b]"I think the guy just

""I think the guy just likes to hear himself talk."

Ayuh,..... I think you're Right......

A BBC is only maybe 150lbs More than the SBCs....

Go for It......"
 
"Jody, without knowing your bo

"Jody, without knowing your boat, it is difficult to say for sure what will happen. What I do know is that most boats suitable for sleeping six people had the option of big block power from the factory.

You are only adding 500-600 lbs. That is equivalent to about 75 gallons of water. I don't see any negative effect, although the boat may handle "different" than before, it may well ride better. You may find yourself adjusting the tabs differently than before, but that's about it.

My main concern would be weather the shafts will take the extra torque. Some boat manufacturers used little toothpick shafts which would not take the stress of BB power. Again, this is all boat specific. Most likely you're fine, but more information on the boat would be helpful in rendering an educated opinion.

Good luck,
Rick

It sounds like your should introduce this guy to the guy on Richie Luther's dock."
 
"Hey, Jody, I'll make you

"Hey, Jody, I'll make you a bet: Properly propped, those big blocks will get BETTER gas mileage than your old small blocks. Want to take me up on it? You can't loose.

Jeff"
 
"Jody,

I can lend my experi

"Jody,

I can lend my experiences to you, Our 34 Silverton was made with 350 Cu In engines that were re=powered with 454's. An easy swap, and our boat rides better, gets better fuel economy and gets up and goes when you hit the throttles. I am still not too sure we are propped correctly but we are running 18x22's with a #3 cup and our wot still can hit 4800. While we are getting closer, I'll live with this this season ...Everything they say is so...."
 
"thanks guys,thats just what i

"thanks guys,thats just what i wanted to hear and from the people i wanted to hear it from.I have never actually driven this boat or even seen it move under its own power so if it does handle any different I sure wont know it.As for the boat it is a 1981 31 foot chris craft convertible,it has 1 1/4 inch diameter shafts that i will have checked for straightness and any other problems before i install them.The props are 15x17's that i have already taken to the shop to make sure they were ok.I told the guy I was bumping up in the horse power departmentbut i have no idea what gear ratio my transmissions are so he added a little cup and said that would be a good place to start.Thanks again guys for taking the time to give me advice and share yor own experiences.I should have known the guy was full of hot air when he told me I didnt need trim tabs and I would probably be better off if I didnt even bother putting them back on the boat.The guy supposedly has had a lot of big boats and that was the only reason I even gave what he said any consideration and second guessed my initial thoughts on the swap.I think if we got this guy and the guy on ritchie luthers dock together they could spend all of their time talking about oil viscosity and boat engineering and leave us the hell alone. thanks again"
 
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