fuel efficient cruising

[Blue_Runner]

They are electric or hydraulic stainless steel flaps on each side of the transom that help control porpoising and makes a better ride. And yes, they do make a big difference.

But to answer your question, you are right in that all the way down isn't the best economy and highest speed / lowest RPM work in your favor. As you trim up more hull is coming out of the water, steering gets easier, speed increases and so on. My trim indicator died, but I can tell by feel exactly how my engine is trimmed.

I don't have a fuel flow meter but I believe the best RPM range for fuel economy on a V20 w/ 150 hp o/b is somewhere between 3700 - 4000 RPMs. In your scenario of going around 20 mph or so I wouldn't worry so much about economy as adjusting the trim for the best ride, including pounding and spray from the hull. I've found there are times when speeding up and adjusting trim you can get on top of the chop and find a better, dryer ride than if you tried to go slower. Not always the case, but sometimes.

[Larryrsf]

Thanks! Saturday was busy out there, every kind of boat including the heavy Harbor Cruise vessels. Lots of sailboats, even skidoos and a few runabouts really flying. So crossing those wakes was scary for my newbie-to-boating wife. I was praising the Wellcraft deep bow for efficiently slicing through most of that stuff. But we did get slammed by big waves a few times-- and since she wasn't standing with knees flexed like I was, she got slammed too, ha. I bought cushions for our "Bluewater" boat seats today. Hope that helps, but standing up is really the best answer to rough water.

Larry

[smokeonthewater]

trim for the highest speed at a given throttle and then trim down if you need to to stop porpoising

[Blue_Runner]

Bean bags!!! Cannot stress it enough. You can get one called the "Big Joe" at Walmart for about $30. Money well spent. You won't be sorry. The lady will hug your neck, I promise! My crew catches quite a few snoozes while I'm at the helm banging the fillings out of my mouth.

[Destroyer]

Originally Posted by Larryrsf

Thanks! Saturday was busy out there, every kind of boat including the heavy Harbor Cruise vessels. Lots of sailboats, even skidoos and a few runabouts really flying. So crossing those wakes was scary for my newbie-to-boating wife. I was praising the Wellcraft deep bow for efficiently slicing through most of that stuff. But we did get slammed by big waves a few times-- and since she wasn't standing with knees flexed like I was, she got slammed too, ha. I bought cushions for our "Bluewater" boat seats today. Hope that helps, but standing up is really the best answer to rough water.

Larry

Just remember that you have a steering wheel to hang onto... she doesn't. If you're standing up in the boat MAKE SURE you both have on life preservers.... Accidents happen, and if you're standing, they can happen faster. Getting tossed overboard by a wave you didn't see coming and weren't ready for is NOT high on the fun things to have happen while boating.
I'm 70, a good swimmer, a certified Red Cross Lifesaving Instructor and I always wear my pfd while underway. NEVER be embarrassed to wear one. Get the canoe/kayak kind that you wear like a vest and has a zipper and wide arm holes and in minutes you'll forget you even have it on.

[jamesbalog]

[QUOTE=Blue_Runner;214237]They are electric or hydraulic stainless steel flaps on each side of the transom that help control porpoising and makes a better ride. And yes, they do make a big difference.

But to answer your question, you are right in that all the way down isn't the best economy and highest speed / lowest RPM work in your favor. As you trim up more hull is coming out of the water, steering gets easier, speed increases and so on. My trim indicator died, but I can tell by feel exactly how my engine is trimmed.

I don't have a fuel flow meter but I believe the best RPM range for fuel economy on a V20 w/ 150 hp o/b is somewhere between 3700 - 4000 RPMs. In your scenario of going around 20 mph or so I wouldn't worry so much about economy as adjusting the trim for the best ride, including pounding and spray from the hull. I've found there are times when speeding up and adjusting trim you can get on top of the chop and find a better, dryer ride than if you tried to go slower. Not always the case, but sometimes.[/QUOTE]

here on lake erie where we usually have a chop speeding up and trimming up keeps things much more smooth and dry

[Larryrsf]

My boat is in a Marina on San Diego Harbor. So I am constrained to do my boating on that harbor. It is big enough that even light winds can kick up chop and even swells. And BIG boats, even ships pass through and create big swells from their wake. So the harbor is seldom smooth enough to plane without scaring the crap out of my passengers, ha.

My boat speedometer shows low 20s with 3000 RPM. It is on top and planning at that speed. I read that this boat with a good 150HP engine can hit 50MPH with just one or two people aboard. Maybe I will find lake-smooth conditions some morning and let er' rip!

Larry

[THEFERMANATOR]

Originally Posted by Larryrsf

My boat is in a Marina on San Diego Harbor. So I am constrained to do my boating on that harbor. It is big enough that even light winds can kick up chop and even swells. And BIG boats, even ships pass through and create big swells from their wake. So the harbor is seldom smooth enough to plane without scaring the crap out of my passengers, ha.

My boat speedometer shows low 20s with 3000 RPM. It is on top and planning at that speed. I read that this boat with a good 150HP engine can hit 50MPH with just one or two people aboard. Maybe I will find lake-smooth conditions some morning and let er' rip!

Larry

An old school 150 should push you close to 40, but not 50. it takes about 200 prop shaft horsepower to get into the 50 MPH range with a V-20. A good healthy late model 150 will get you low to mid 40's top speed. A 225 in healthy condition will break 50 with a good prop. And if your crazy enough a 250 can hit 60.

[Larryrsf]

Not sure how accurate my speedometer is in the 40s. It is right on at 10MPH and 20MPH, checked against a GPS. But I was way too busy to cross-check the speedometer against my cell phone Boat Buddy ap at full throttle. The tach showed 5000 RPM and the speedometer jumped up to mid 40s. And that with the trim all the way down. I was alone in the boat and nothing with any weight was aboard. I don't know which prop I have. Someone said the engine should turn 5500 with the right prop.

Someday I will take it out early in the morning when the harbor is glassy smooth and see what it really does.

I hope to install a Garmin GPSMAP 2010 soon. It should read out accurate speed.

I am still wrestling with fuel gauges. I installed new SeaSense senders when the tanks were out. I brought the wires out to the dash. But I have been unable to get readings that are make sense even though I tried three different gauges. The previous owner of this old boat used a piece of round doweling to sound the tanks, pretty "old school" method. He had the stick marked at full and half full, which would be 20 and 10 gallons. That actually works, ha. And it is pretty reliable information!

Larry

[bradford]

I actually like the dowel idea, know a couple charter boat guys that use it. Keep in mind a belly tank gets smaller towards the bottom. 1000 idle speed is a little high. I may be wrong, but I thought 700-800 was about right.