Offshoreonly.com - Engine Shop

Offshoreonly.com (https://www.offshoreonly.com/forums/)

- Checkmate (https://www.offshoreonly.com/forums/checkmate-53/)

- - Engine Shop (https://www.offshoreonly.com/forums/checkmate/140014-engine-shop.html)

Quote:

Originally Posted by RJBBC

Thanks Jeff, I am trying to justify the expense. The best I have come up with so far is less money to spend on the next power upgrade.

Are you thinking about supercharging? I have seen a few used procharger set ups for sale lately. Unfortunately, many of them were for carb set ups.

Quote:

Originally Posted by Magic Medicine

Are you thinking about supercharging? I have seen a few used procharger set ups for sale lately. Unfortunately, many of them were for carb set ups.

I am not sure what we will do. We may stay with our current short block, rebuild and supercharge. The other option would be to start fresh with a larger displacement NA motor. The good news is we have several years to think about it. :D

Quote:

Originally Posted by RJBBC

I would like to see my boat run faster, but I would rather have a bigger boat. I guess I will keep mine the way it is until I move up. You know you can never have too big of a boat for Lake Michigan.

Quote:

Originally Posted by Magic Medicine

I would like to see my boat run faster, but I would rather have a bigger boat. I guess I will keep mine the way it is until I move up. You know you can never have too big of a boat for Lake Michigan.

A smaller boat is easier on the retirement fund and takes more driver skill in rough water. :evilb:

Quote:

Originally Posted by RJBBC

A smaller boat is easier on the retirement fund and takes more driver skill in rough water. :evilb:

I hear ya, but NOTHING BEATS A CIGARETTE! :evilb:

Here are a few more pictures of the Checkmate. The boat behind the Checkmate is currently one of the faster boats on our lake.

Quote:

Originally Posted by checkmate454mag

Rob,

I dont understand those numbers either. More power to you if they are right but the facts are below.

(((pitch x rpm) / ratio)) / 1056= theoretical speed
Then add in slip.

your numbers are as follows, assuming a 1.5 ratio drive..

24.5 x 5000= 122500
122500 / 1.5 = 8166.66666
8166.666 / 1056 = 77.33
So 77.33 is theoretical speed without slip factored in. If you are actually running 72.3 then your slip is only 6.5% . That would be great . Unfortunetly, most likely impossible. Here is a for instance.. I am running a Hydromotive P5-X and am getting 9.5% slip.

It is that time of year to start looking at your trailer and maybe even pull out last year's boating magazines because you have memorized all of this year's. Well here is some food for thought on slip percentages found in the September 2005 Powerboat Magazine under the 525EFI Dogfight article. Eliminator 27 Daytona 81.8mph@5200rpm=80.4mph theoretical speed :eek: , Hallet 255 Open Bow 75.3mph@5000rpm=77.3mph theoretical speed or 2.6% slip, Laser 25 Fury 77.1mph@5200rpm=80.4mph theoretical speed or 4.1% slip and Shockwave 25 Tremor 79.8mph@5300rpm=82mph theoretical speed or 2.7% slip. The above four boats ran 525EFIs with Bravo XR drives with 1.5:1 gear ratios with Mercury Bravo One 15 1/4" x 26" props. Any ideas on what's going on? Go Bears :drink:

Yeah, magazines lie like hell!! How can they claim to be on the positive side of slip???

Quote:

Originally Posted by checkmate454mag

Yeah, magazines lie like hell!! How can they claim to be on the positive side of slip???

I agree magazines to have keep there readers and advertisers happy. I am sure at times that is a delicate balance. The Eliminator 27 Daytona is a very efficient single engine IO hull but all of the boats they tested for that article were flying. I wonder if they were running the boats in salt water. How much speed will your boat gain by running at sea level in salt water vs. 1000ft elevation in fresh water? How much less slip should you expect on the same boat running in salt water vs. freshwater?

While I have never had the opportunity to test in fresh water, I have not heard of any measurable difference in performance between fresh and salt water. Altitude is another story. As anyone would expect, the loss of horsepower attributed to altitude only increases the higher you go. I am sure that it exists, I dont know of any actual formulas that can measure the loss at specific altitudes.