210hpCummins question

[DRIFTER31]

First off this site is a pleasure to read, I dad a 28bertram,28topaz,36i hate to admit TROJAN.{weakest boat} Now i am restoring my last boat 31Tiara. I bought 2 new cummins 210hp6bts 1.5 gears and cant find anyone who has these in this boat. I figured some of you Bertram gurus might know how to prop this boat. No tower express model. 15000lbs loaded. And how should it compare speed wise to the 31Bertram. Thanks for your time and advice TROY DANOS

[capy]

First off this site is a pleasure to read, I dad a 28bertram,28topaz,36i hate to admit TROJAN.{weakest boat} Now i am restoring my last boat 31Tiara. I bought 2 new cummins 210hp6bts 1.5 gears and cant find anyone who has these in this boat. I figured some of you Bertram gurus might know how to prop this boat. No tower express model. 15000lbs loaded. And how should it compare speed wise to the 31Bertram. Thanks for your time and advice TROY DANOS

Depends on what year the tiara is...the early ones had an 11 degree deadrise tha make for a fast fuel efficient boat provided the seas are flat. Sometime around 1992 the changed the hull to a 16 degree deadrise which made for a smoother ride at the cost of efficiency.

Walter Kaprelian has 210 is B31 and I think he has 21x20 and cruises at 21 knots, I think.

My B31 has DD6V53's 216 hp apiece and cruises at 21-22 knots with 21x19's and 1.5:1 tranny's(no tower or hardtop)

I'd go with square 21x21 to start with based on less deadrise of 16 degrees, if you have the older 11 degree model, try something over square.

good luck.

[DRIFTER31]

My boat is a 1986 model. and i have a pair of 4blade 20/22 i might be wrong but i dont think i can swing that much wheel. Do you think a Bertram31 is easier to push. The Tiara is 12ft wide. I was thinking of pitching to 20/20 for the sea trial. I would hate to have too much wheel for that. Any input???

[John C]

I have also owned several bertrams and now own a 1988 31 tiara that I repowered gas to diesel over the winter of 05/06..the bottom is 16 degrees on the older (pre 1992) and 18 degrees with prop pockets after that. Shoot me a private message with your phone and I can go over what I learned when I did my repower. John.

[Bruce]

Drifter,
Do yourself a favor.

Talk to your local prop shop and give him the details of the boat and engine/gear combo.
They will plug it into their formula and come up with a prop size.

I repower all different size boats.
This is one of the first things I do before I even start because that prop will also give me some idea of boat performance.

Guessing and having work done to your wheels is uneeded expense plus once wheels are tweaked a certain amount of times, thats it they're done.

[In Memory Walter K]

My31 Sportsfisherman is a heavy older Bertram. My 210 6bt's have 1:1.5 trannys and is propped with 20 x 20 cupped Nibrals and cruises at 20-21 kts.
I suspect she's a bit underpropped but I'd rather have it that way. Walter

[DRIFTER31]

Thanks for everyones input. Walter was that 3 or 4 blade 20x20 wheels?

[In Memory Walter K]

They're three bladers. Walter

[DRIFTER31]

Thanks Walter i will try 20x20x4 and let you know how she runs