Viking/Merc Bridgeport & Prop Slippage

Iíve got a Ď78 Viking that has been lightened quite a bit.   Klegecell flooring, reinforced transom,  even sanded some of the glass out of the deck and in other places to make it lighter.  Iíve added a 6in slidemaster plate and I am considering centering the steering.  Iím running a 2.4L BP Merc, shaved the heads .060 , opened the exhaust, bumped the timing, put on a Holley bluepump @ 5psi, and added a Bobs Nosecone and land and sea plumbing kit. Iím turning a new Mazco RE3 29pitch 7300 and my hole shot is killer (pulls the prop over to 8000 out of the hole).   The center of my prop shaft is approx level with the bottom of the pad.  How fast do you think Iím running and how much slippage should I expect?   Any of your ideas and suggestions would be appreciated.

Barton

P.s. For what its worth, I grew up driving a Vegas, and Hydrostreams are the best performance boat on the market. Bar None.

 

Barton,

Boy is this a topic that will turn a few people blue. Prop slip. I feel you are in the mid 90's with 8 or 9% slip. Why? Most Mazco 29's are on the light side of 29 so unless we know the EXACT pitch of your prop it is all a guess anyhow. Understand that slip is GOOD. Without slip you would have no thrust. The lower the slip number the less thrust. The desired slip is determined by boat drag or load, speed attained, horsepower, prop design (a bad blade design or choice will produce excessive slip without thrust) angle of attack, prop attack angle, and a ton of other things. In a perfect world, the heavier the boat, and the less the horsepower, the more slip needed to push the boat. (just like airplanes). Anyhow I could go forever on the slip thing, but my point is not to get caught up in the slip factor too much. As long as your prop works good I'd be happy. Sounds like yours works great. To help keep the motor from revving to 8000 on take-off, have the prop "rolled". This is a slight depitching of the leading edge. The boat will accelerate harder than ever before with the same top end. I'd send it to Mazco and tell them to add acceleration as John Mazar calls it. That's his word for the "roll". Be careful not to have too much put in as it will hurt top end if excessive. The rest of your set up is spot on. Lastly, try and find a GOOD 30" cleaver if you can as it might get you to 100. The cleaver will make the V-King lay down at top end to get that last few mph's.

 

 

Please submit whatever questions you have to IHRTechTalk@yahoo.com.  All questions and answers selected will be displayed on this page as they come in.  Note: though all boaters are welcome, priority may be given to I.H.R. members.  Randy can not be held responsible for any advice given.  Though his information and expertise is second to none, he has no control over what you do with your boat.  It is up to you to boat safely and act responsibly, and his advice is only to be used as a guidance for your high performance boat/motor of which you are the one responsible for the risks involved.

Thanks,
Mark C.

 

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