270 cruis speed and mpg?? twin inboards

[captseasick]

so am I the only one with a 270 on here?? if not and you have a 270 with twin 350 inboards let me know... What is the cruise speed at 3200 to 3500? and what kind of MPG do you get???  My plan is a repower with 350s at 310hp and try and rework the props for a little more speed at cruise... so a little better mpg... if you have done this pls tell me what worked for you... Thankss!!!

[captseasick]

nobody?? theres got to be atleast onemore 270 out there lol

[seabob4]

There are others, Seasick, just not too many...and how often they come on here is anybody's guess...

[gran398]

If it's any help, have a vintage 34 Hatt with twin 454 Crusaders, 350 HP each.  Somewhat similar to your ride, but a higher burn.

 Can't quote at present mpg at cruise. Will know more this spring, but likely around 1.5-1.6.

Your cruise should be around 24 statute mph at 3400 rpm with the small blocks, and higher mpg.

[captseasick]

whats the weight of your 34ft hatt?  From what I have seen the 270 weighs 6k dry and 8k with fuel.... atleasts that what a magazine page that was selling on ebay said... and that was boat magazine (unknown which one).  Im building 2- 310hp- chevy 350's and I am hoping with the extra hp I can cup the props or go a step or so bigger and drop the rpms by 200 to 400rpm at a given speed and then run the rpms back up to normal cruise rpm ( 3200 to 3500) which inturn will increase speed and hopfully MPG... worked on my 23ft Fourwinns... went from a 17pitch to a 19 pitch with a little more cup and now cruise at 28mph at 3500 rpm and get 2.6mpg.... with the 17pitch I cruised at around 24mph... not sure on mpg with that... need to see one day... but trying to sell her now :(  Trying to get the 270 to a 28mph+ cruise and around 1.8+ mpg......

[SonShine Fishing]

I had a 21 SeaRay with 350 chevy Mercruiser. Rebuilt the 260 horse engine and ran for several years. Built a Vortec 350 with GM marine roller cam, Edelbrock Performer EPS intake and Edelbrock Performer marine carb. Fuel economy went from about 2 MPG to about 2.5 MPG on the same prop. Had a fuel flow meter on the boat and fuel consumption started climbing pretty fast above 3100 RPM. Would run 29 MPH or 24 Knots at 3100. Seemed to do best about 3000 RPM. Main point I think the Edelbrock carb in place of the Quadrajet was the biggest source of improvement. I am an ASE master tech, built both engines and the quadrajet, Edelbrock was brand new. I think from memory was pulling about 11 inches of vacuum at 3000. Burn about the same amount of fuel per day in our TM 290 as that 21 SeaRay but Diesels make a big difference when you do a lot of trolling.

[giorgos]

whats the weight of your 34ft hatt?  From what I have seen the 270 weighs 6k dry and 8k with fuel.... atleasts that what a magazine page that was selling on ebay said... and that was boat magazine (unknown which one).  Im building 2- 310hp- chevy 350's and I am hoping with the extra hp I can cup the props or go a step or so bigger and drop the rpms by 200 to 400rpm at a given speed and then run the rpms back up to normal cruise rpm ( 3200 to 3500) which inturn will increase speed and hopfully MPG... worked on my 23ft Fourwinns... went from a 17pitch to a 19 pitch with a little more cup and now cruise at 28mph at 3500 rpm and get 2.6mpg.... with the 17pitch I cruised at around 24mph... not sure on mpg with that... need to see one day... but trying to sell her now :(  Trying to get the 270 to a 28mph+ cruise and around 1.8+ mpg......

What ever happened with this project. I also got a 270TM  with 260 HP and i get very bad MPG and very low cruise speed(20 MPH@ 3200 RPM)

[challengesea]

What ever happened with this project. I also got a 270TM  with 260 HP and i get very bad MPG and very low cruise speed(20 MPH@ 3200 RPM)
[/quote]

Is yours a single or twin engine?