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sea bitt
USA
63 Posts |
 Posted - 07/09/2007 : 3:21:16 PM
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At what speed do you cruise at?
I run at about 3200 RPM and 22 MPH with twin crusader 220s. I have a hard time keeping on a plane if it drops below 2900 RPM and about 17 MPH using the trim tabs. I was wondering if you get the same results? Better or worst?
Bruce
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Rockmeister
USA
307 Posts |
Posted - 07/09/2007 : 9:20:01 PM
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I have been watching this closely lately, as I just added a Lowrance Fuel management computer.
I tend to run about 22 MPH at 3000 RPM.
I can run down to about 2400 RPM after I'm on plane and it stays on plane. Hadn't noticed the speed at that RPM, it's probably about 17 MPH or so.
Mine is more efficient at about 3000 RPM, so I tend to stay there as conditions allow.
I'm just now gathering info with it, will let you know as I learn more!
Hope this helps! 
79 28' Mariner twin inboard V-drive.
SW Lake Erie: Maumee Bay & The Islands |
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EXW
USA
72 Posts |
Posted - 07/10/2007 : 12:00:59 AM
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I have a '76 w/ twin 302's (351 heads)& I get to about 19-21mph (depending on wind/current)at about 1850 to 1900 rpm's. Since I have little ones down below I rarely push it past this point unless I am without my girls...
Erik
"Sea Sharp"
Seattle, WA |
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Rockmeister
USA
307 Posts |
Posted - 07/10/2007 : 10:46:23 AM
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Wow Erik!
Compared to mine, thats a low RPM for that speed!
Is that a gps speed or paddlewheel speed?
I'm curious what kind of mileage you get at that speed.
Do you know what props you have?
If you do well with it, I may re-prop.
I also have twin 302's and tend todo 2500-2600 RPM for 19-20 MPH.
Are we talking nautical miles or statute miles?
(My numbers are in statute miles.)
79 28' Mariner twin inboard V-drive.
SW Lake Erie: Maumee Bay & The Islands |
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EXW
USA
72 Posts |
Posted - 07/10/2007 : 6:42:07 PM
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About 10 to 10.5 GPH at that speed...I was surprised by this return on my rpm's so I replaced the tacs and then I used my friends 2007 GPS to verify speed. I am sticking to my guns on those numbers ;-)
I am pulling the boat tomorrow for a quick bottom paint and I need to check the shafts & prop as I am feeling a slight vibration - may have hit a log - anyway I'll check on prop size and get back with ya...
Erik
"Sea Sharp"
Seattle, WA |
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Rockmeister
USA
307 Posts |
Posted - 07/11/2007 : 11:46:13 AM
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Cool! Thanks Erik!
Is this number for one engine, or both total?
I'm running 16 GPH at best(8GPH per engine), which seems to be around 3000 RPM.
If I could lower that by that large a margin, new props would be worth it!
79 28' Mariner twin inboard V-drive.
SW Lake Erie: Maumee Bay & The Islands |
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EXW
USA
72 Posts |
Posted - 07/11/2007 : 11:25:45 PM
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Thats 10 to 10.5 GPH TOTAL for me since I bought the boat. I did tune it up and changed fuel filters but that's it. I use unleaded regular too. (Rockmeister) Below is an unedited e-mail from the previous owner of my boat that I stay in touch with. I don't like to spin fish stories so I thought I'd call in reinforcements!
PREVIOUS OWNER WRITES:
10 gph was the best it ever got. And that's 5 gal per hour per engine. The faster you go, the more the boat is up out of the water and the better the economy. We were in a hurry to get home from the San Juans. I filled it at Cornet Bay at Deception Pass with 89 octane, checked the time, and traveled nonstop south to Desmoines. I checked the time as I pulled up to the fuel
dock and then filled up again. It was right at 10 gals per hour. I couldn't believe it because it normally got about 12
Erik
"Sea Sharp"
Seattle, WA |
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Rockmeister
USA
307 Posts |
Posted - 07/12/2007 : 11:25:52 AM
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Hey Erik!
Thank you for the info!!!
I not doubting you at all, just want to make sure we are talking the same language! lol
Definitely would be interested in what the difference in your boat and my boat is, in that your mileage is almost double mine!
Mine is a 1979.
My engines are Inboard 302's also currently with points, have ordered the electronic ignitions, however haven't received them yet... 
Would be very curious about the props, and the ignition advance. Other than the carbs, there isn't much else that I can imagine changing it that much...
Looking forward to exploring this further. 
79 28' Mariner twin inboard V-drive.
SW Lake Erie: Maumee Bay & The Islands |
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Jerry
USA
64 Posts |
Posted - 07/12/2007 : 8:55:44 PM
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| Can anyone with a mid 80's boat give me some numbers at to MPG or most fuel efficient cruise speed?? I purchased a Navman fuel system, but am still having problems getting it working. Have been threw 4 senders and 2 head units and still having problems. I had one on my old boat and loved it ... but it is not helping me with this boat. I do not have much experience with this boat planed off. Can anyone help ... looks to me that I am running about 1.2-1.3 Gallons per mile (Statue) ... anyone have different numbers? Thanks a bunch .... |
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Rockmeister
USA
307 Posts |
Posted - 07/12/2007 : 10:54:35 PM
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Hi Jerry,
I just installed a Lowrance LMF-400 Multifunction Guage (Used for Fuel management mainly).
Can say it was a breeze to install and worked perfectly the instant it was fired up!
(And it cost less!)
Gotta love that!
The best I have gotten is about 1.2 Mpg That equates to about .83 Gallons per Mile.
This is at about 3000 RPM.
Erik is doing much better than either one of us and is getting info for us about how his boat is set up. I believe he is getting about .5 Gallons per mile or 2 MPG.
(All my miles figures are in statute miles.)
Rock
79 28' Mariner twin inboard V-drive.
SW Lake Erie: Maumee Bay & The Islands |
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Rockmeister
USA
307 Posts |
Posted - 07/12/2007 : 10:57:00 PM
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PS My electronic ignitions and coils were here when I got home!
Cool! I can get them in this weekend! Yeah! (I think, more work, lol)
79 28' Mariner twin inboard V-drive.
SW Lake Erie: Maumee Bay & The Islands |
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Rockmeister
USA
307 Posts |
Posted - 07/16/2007 : 10:25:15 AM
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Installed the Pertronix electronic ignitions and the Pertronix Flame Thrower coils Sat. The coils are a 40,000 Volt epoxy filled coil requiring no external ballast resistor.
What a big difference!
The engines now have a strong spark!
You can see a huge difference with the timing light.
The spark is now strong and consistent.
Best thing is, you can hear the difference in how smooth the engines are.
Just touch the key and they fire right up.
I did find that the timing was way off on both engines prior.
I'm curious what everyone has their timing set to?
The sticker on the 302 calls for 10 degrees BTC @ 600 rpm.
That seems a bit low for a non-direct connect drivetrain, so I set mine at 12 deg BTC.
However the distributors don't have vacuum advance, so I am in the air on this...
I also found that I was getting even slightly better economy at 3500 RPM at about 24 MPH this weekend.
I may find a knock sensor and advance the timing until the engines barely knock under load then back the timing off a couple degrees.
(This gives the most horsepower and economy from the engines.)
(I found this inexpensive knock sensor)
http://www.viatrack.ca/
79 28' Mariner twin inboard V-drive.
SW Lake Erie: Maumee Bay & The Islands |
Edited by - Rockmeister on 07/16/2007 11:49:13 AM |
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Rockmeister
USA
307 Posts |
Posted - 07/17/2007 : 12:12:31 PM
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Hey Erik!
Did you get a chance to check what props you have by chance?
I have another question, the 351 heads don't usually add too much to a 302 unless they are smaller chambers, enlarged exhaust valves, modded, or used with a longer duration exhaust cam lobe.
(With the above mods together, the 351 heads can add alot of horsepower AND up the mileage.)
I'm curious why the 351 heads were added to the engine?
Another question... lol
Sorry for all the questions, trying to figure out what you have exactly and change mine accordingly, if it is feasible.
Do you have vacuum advance distributors?
Like this one in the pic with a vacuum line and the vacuum motor(canister) hanging off the distributor? http://www.highperformancepontiac.com/tech/vacuum_advance_tech/photo_01.html
Ordered the knock sensor BTW, more the ignition is advanced WITHOUT knock or ping, the more mileage and power.
Thanks! Rock
79 28' Mariner twin inboard V-drive.
SW Lake Erie: Maumee Bay & The Islands |
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EXW
USA
72 Posts |
Posted - 07/17/2007 : 11:26:37 PM
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Sorry about the delay. With any luck I will get the props back tomorrow and measure them then. I need to get my boat back in the water as we have a trip planned to Whidbey Island this Friday. I will measure the prop diameter when I get them back.
Also, I will double check later this week but I am 95% sure that I do NOT have vacume advance units on my 302's... I was told that many of the 302's were outfitted at the factory with 351 heads (in cars - many mustangs were set up like this). The mechanics I knew back then always told me "with the 351 heads, the engine doesn't have to work as hard to generate the same horse power". I realize that is not an A+B=C answer but that is what I was told. I call my Dad on his birthday tomorrow and see if I can get some specifics out of him! I'll post again in the next few days with the prop size...
Erik
"Sea Sharp"
Seattle, WA |
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Rockmeister
USA
307 Posts |
Posted - 07/18/2007 : 12:49:47 AM
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Thanks Erik!
The prop size (diameter, pitch, and manufacturer) should be stamped on the hub.
Rock : )
79 28' Mariner twin inboard V-drive.
SW Lake Erie: Maumee Bay & The Islands |
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EXW
USA
72 Posts |
Posted - 07/20/2007 : 9:15:56 PM
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Rock -
Well - as is often the case with boating - not all went as planned. My props, shafts and couplers did not arrive this morning at the boat yard. Coincidentally, our area is receiving some surprise thunderstorms so we postponed our Whidbey Island trip anyway! I should get the boat back together and in the water on Monday afternoon. Its been great having her out of the water for a week. I did so many "little things" and the new RED bottom paint looks amazing. I can't wait to run her next week. I will still get that info to ya then. Have a good weekend all!
Erik
"Sea Sharp"
Seattle, WA |
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Topic |
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At what speed do you cruise at?
