31 bertram with 210 hp cummins

[jcox1273]

I have a 1962 31 Bertram express with 330 hp crusaders. The boat runs and performs great! (650 hours). I have a opourtunity to purchase a pair of 210 horsepower cummins with transmissions, and one of them has a trolling valve. (1000 hours). I would like to receive some input from anyone who has a similar power plant. Gear ratio? Prop size and pitch? 3 or 4 blade? Cruising speed at how many rpm,s ? top speed at how many rpms.? This is my first time on any forum, so please excuse me for not doing what I am supposed to do. I would also like any other advice that can be provided. Thank you in advance: jcox1273

[longfin]

I have a 1975 Fly Bridge Sport Fish with 210 Cummins. My boat is Fairly Light, no tower, Glass Tech Deck and a Glass Tech windshield insert. I have Twin Disc 5011A Gears that are 1.52:1 I believe. These Gears are shit by the way. My Props are Michigan Wheel Dynajet 20" X 20" 3 blade with a Number 4 Cup, shafts are Aquamet 22 1.375". The last time the boat was hauled for a bottom with 1/2 load of fuel I was tipping the scale at 11,500 lbs. prox.

I cruise at 1950 RPM all day long and that nets me a solid 20knot cruise, doesn't matter if it's loaded or empty, tabs make little difference. I'm on the west coast so 20 knots suits me just fine most of the time. The boat certainly feels better at 23 - 24 knots. Next go around if these 5,000 plus hour motors ever let go I think Cummins 330's would be a good fit. I have not a thing to bitch about reliability and economy are Honda Accord like. I have done injectors and turbos and other than oil changes, zincs, and coolant

[Carl]

jcox1273--

Stay away from them...but if you would not mind sharing your contact with me first

Do a search here on Cumming motors and you'll soon see they are probably the best motors for the 31.
Some will argue a little more power is better...I see their point.

Fuel sipping 210's I'd buy for my 31 in a Heartbeat.
As for Cummins in general, they are dependable, parts are easy to find and not so bad on the wallet, many mechanics know them.

Welcome aboard
Carl

[Tony Meola]

Maybe Tom will see this, since he just repowered his 31 with the 210 Cummins about two years ago.

Yes they sip fuel, but going from the 330's to the 210 will be a big difference. You probably cruise between 26 to 28 knots, you will be dropping down to about 20 knots.

For some reason I think Tom used the ZF Transmissions.

[Tony Meola]

http://bertram31.com/newbb/viewtopic.ph ... s&start=50

I found one of Tom's posts. Take read through it. There is some discussion on Transmissions.

[Carl]

Yes they sip fuel, but going from the 330's to the 210 will be a big difference. You probably cruise between 26 to 28 knots, you will be dropping down to about 20 knots.

Tony, he has 330hp mercruisers, believe he is talking gas motors.

With my 330hp gas, Chrysler 440's there is no way I am cruising 26-28 knots...unless its from fuel dock to fuel dock.

[jcox1273]

you are both correct and incorrect. the engines in my boat are both gas. at 2900 rpm's the boat will run 19 kts. wide open throttle is 4600 rpm's. the boat will run 35 kts. anything above 3000 rpm's the gas absolutely pours out. that's why i want the diesels. and thank you guys for your comments.

[1962 31]

I put them in and they are great no speed demon but 14 gallons and hour total at cruise is great
I cruise 20 knots at 2200 rpm 22 at 2400 and top out just shy of 26
zf 63a trans 1.5 ratio 3 blade 20x22 props going to play with the props when I get some time give them more pitch as I can easily hit 2650 rpm fully loaded now

[mike ohlstein]

you are both correct and incorrect. the engines in my boat are both gas. at 2900 rpm's the boat will run 19 kts. wide open throttle is 4600 rpm's. the boat will run 35 kts. anything above 3000 rpm's the gas absolutely pours out. that's why i want the diesels. and thank you guys for your comments.

Do you still have the original 170 gallon fuel tank in the boat?

[Tony Meola]

Missed that one Carl.

When we had the Big Blocks cruise was 19 knots at 2900 also. Gas burn was about 25 an hour. 270 Cummins, ups the Cruise at 2400 we at running at 24 knots. Top out at 2650 and 30 knots.

[Carl]

Missed that one Carl.

When we had the Big Blocks cruise was 19 knots at 2900 also. Gas burn was about 25 an hour. 270 Cummins, ups the Cruise at 2400 we at running at 24 knots. Top out at 2650 and 30 knots.

My gassers are a little tired so I cruise about 17-18knots at 2950 burning 22-23gph.
Big difference is swells, I need to bump up the cruise to climb the backs as they get steeper or I fall off plane were diesels could care less if going up or down.
That and of course the fuel burn.

It would be great to run 24 knots, but would be a very happy camper at a consistent 19-20 burning a 1/3 or so less...much less if you consider a trip out with full tank and gear I need to bump up the throttle a good amount to carry the extra load at speed.

ahh..someday.

[Charlie J]

carl you had your chance lol

[Carl]

carl you had your chance lol

I know I know and I know I'll only get so many chances handed to me like that.

Believe me I tried to figure a way to make it work...and what really hurt is it was just so close to being doable.