74 SF with non turbo 903's speed

[Daybreak]

The more I read the more I wonder if we are getting the most out of Daybreak. The bottom gets cleaned once a month. The 903's run great, some smoke buy not too bad, but we are only getting 12-14 knots at 80% WOT. If that's it then its ok, just seems slow, but then again the 903's are only making 300 HP a side.

Ben

[REBrueckner]

Bill Allen's 43 MY with 310HP 6-71's gave a 16+ knot approximate WOT speed on our recent trip to Florida with at least half full fuel and water. So your statistics seems about in line.

The seventies Hatts are all built like a tank and underpowered by modern standards....I don't think they could fit in engines with enough HP to really get most of them moving...and customer speed requirements were more modest back than as well...

Perhaps someone else with your model boat and engines can provide a more precise comparison...

[Daybreak]

Couragous- '69 38 SF- has non turbo DD 671's and gets 16-17 knots too. Chris takes great pleasure is reminding me he's faster.

Anybody elso have a 73-74 SF with non turbo 903s with some speed/performance data?

[kwerges]

My 1975 42C has VT903's (turbos) at approx 400hp per side. With turbo 903's
my cruise is 16kts at 2100rpms, so you're not that far off with the lesser hp. Remember these 903's weigh a whole lot more than the Detroits.

[Boatsb]

My 1975 42C has VT903's (turbos) at approx 400hp per side. With turbo 903's
my cruise is 16kts at 2100rpms, so you're not that far off with the lesser hp. Remember these 903's weigh a whole lot more than the Detroits.


My 8V52 naturals at about 280 HP supposedly weigh 2200 lbs a piece. What do the 903"s weigh?

[shark 1007]

Scott

They are closer to 3000 lbs, give or take a couple hundred. They are enormous machines.

[kwerges]

I've been told they weigh close to 3600lbs, although I've never verified...

[habanero]

Ben,

At 12-14 knots is the boat coming onto a plane or just pushing a lot of water. 12-14 knots on my 55C is my least economical speed and hardest on my 12v71's. Do you know your prop size and pitch?
Courgeous is making that speed because he's getting out of the hole. I don't think you are.

Mike
55c"Habanero"

[Daybreak]

The 903's do weigh a ton and some change. Dont know about the props other than they are 24 X 24's. I usually throttle up quickly out of the no wake zone to get on plane and can tell at 12-13 knots Im not in the hole anymore. Perhaps I've been spoiled on Habenero, Ohana, and Stella Maris-all turbo boats.
By the way, last week coming back in the slip my starboard Capital Gear tranny didn't like going into reverse. It just didn't want to engage as smoothly as usual. Thats the beauty of Daybreak, she offers problems and solutions nearly at the same time. Just when I thought she had a prop/performance problem it turns out that if the transmission doesn't engage, you really don't have to worry about speed anyway. Thank you love.

Ben

[Larry B.]

God am i glad to see im not alone!!:D!!
I have a 1974 42convertible with those naturals 903's;
they run great but wish it would be a bit easier to maintain and get parts. I get 15 knots cruising at 2150 and 20 kts WOT (2600rpm) with 24X26 propellers. Hope it helps. Port engine temperature 180 and starboard 188, how are yours? I'm always looking up in ways to keep mine top knoch, let me know please if you have any issues with yours, im in Florida :)

[Daybreak]

Parts can be a challenge but so far between e bay and a guy that knows a guy I've been able to get pretty much every part required. Cummins Cal Pacific also can order parts. Daybreak was outfitted with early model 903's that have some of the same parts as the 370 I think it was. I just flushed the heat exchangers and tranny coolers and have solid running temps at 178-182. Exaust gas temps between 900-1000 at cruise. Don't think I could get 20 knots over Niagra.

Ben