Outboard Powered

[nebulatech]

I'm wondering, are you plumbed (or plan to be) to the existing 20 gallon fuel tank?

[ssrig]

What kind of fuel consumption are you seeing? I expect that it will be much higher than the diesel for the slower speed posted. Also how did it handle at the 11 mph speed?

We had some pretty big winds and following waves this summer, had to slow down on one run so that when we were surfing down a wave we didn't get past the trough and go sideways. Like you say sprightly dancing of the wheel.

The waves from all directions is common in Georgia Straight when the wind and waves oppose the current and is something I avoid in our boat, that gets too exciting!

[ssrig]

This gives a bit of an idea of the consumption

Select Yamaha Outboard Test Model Stroke Fuel consumption WOT
Yamaha 25 HP 4 stroke 9.45 LPH
Yamaha 50 HP 4 stroke 18.5 LPH
Yamaha 70 HP 2 stroke 27.5 LPH
Yamaha 90 HP 4 stroke 34.4 LPH online:

3.78 litres per US gallon so 25 horse at WOT burns 2.5 gallons.

[dkirsop]

Just topped off the tank before hauling my boat tomorrow. Average fuel consumption for the year 1.1 L/hr. Typical cruise 6knts average at 1600rpm. I'll keep my diesel!

[jerridsc]

A mercury outboard fuel consumption chart I just looked at for a 25hp, 4 stroke, EFI running at 2250 rpm’s uses .42 gph. I believe that figures to @8hp to get to hull speed for an A25. “Your results may vary”. When I did my 1/2 hour test run, i had a portable gas tank strapped to the swim platform. Didn’t keep track of usage at all, just speed. I do plan to plumb the existing fuel tank to the engine in addition to another 18gallon tank for extended range. I don’t expect my outboard to be as efficient as the diesel’s, however there are some advantages, quieter, simpler, less expensive (in the short run) cleaner etc. Solar on my hardtop to compensate for fewer charging amps. I am a big fan of the A25 in its original iteration and its advocates. My boat came without an engine. I would never have been able to afford the $15 to $20 thousand to repower with diesel. This way, I can at least get out on the water and, hopefully, see some of you there.
,

[Ambler27FC]

Adding a blower to clear out any gas fumes when you switch to internal tanks? I am not familiar with the A25, but my A27 is not equipped. Best of luck with the new engine!

[jerridsc]

My understanding of blowers for gas engines, they are required when the engine is in an enclosed space as with i/o or inboards, not externally mounted outboards. The fuel tanks are vented to the outside of the boat, same as for diesel. Someone tell me if I am wrong.

[dkirsop]

ANY source of inboard leakage, be it a faulty fitting, a poorly clamped hose, a wear point resulting in tank leakage, a pinhole failure in a seam weld or even fumes that drift on board while filling your tank will result in explosive vapours collecting in the bottom of your hull. PLEASE if you are going to store gasoline in-board (and propane for that matter) install a bilge blower in your boat. This is an inexpensive addition that can save the lives of you and your loved ones. Make sure it draws air in from the lowest point in your hull and discharges overboard in a location that prevents the vapour from drifting back in. Growing up on the coast I can confirm that catastrophic boat explosions as a result of vapour collecting in the hull are very common. Multiple events occur every year in communities near where I live. The ignition can occur from any spark and does not require an engine in your boat.

[nebulatech]

Could one not use the existing engine vent tubing, which is plumbed aft? Not the exhaust, but the vents in the engine bed?

The majority of boats with outboard engines have internal tanks, and the boat building industry has been shifting to outboards for some time.

Jerridsc, how did you choose 25hp? Would 30hp be better? What is your prop pitch? The motor I ordered has a 10" x 10 pitch.

[jerridsc]

Weight of the engine aft was a concern, not wanting to disrupt trim too much. In choosing the 25hp “bigfoot”, like a high thrust version of other outboard brands, I felt it was a good compromise of weight/power. The lower unit has a shaft ratio of 2.5/1. Less speed, more torque. It will accommodate the same prop as their 40 and 50 hp engines; 12.5” diameter, 8 “pitch meant for pontoon or workboat applications, that’s Mercury outboard info. My first water test proved It to do all I hoped it would. It handled fine at top speed of 11mph in mostly calm conditions however I have very little experience with the boat in water (30 minutes). I expect it to ride lower in the water when I have the forward water tank full, the chain and anchor installed, 4 battery house bank where engine was and all the other weighty items I will add.

[jerridsc]

I will also install gas vapor detectors in bilge areas to alert me to their presence in addition to doing all the right procedures when installing such volatile fuel, as has been done in many, many boats over many, many years now. I believe it can be done safely. I thank you for your concern.

[NickScheuer]

Drove up into Blanchardville yesterday to see Scot's boat. He's done some impressive work! Were my MD17C to need replacement I would consider conversion to an outboard in the interest of cost.

[nebulatech]

Food for thought; the idea of an outboard-powered trailer-able pocket trawler is NOT unique to us. In fact, its gaining traction. The boats in the below link are all modern planing hulls so their engines are in the big leagues (150hp+):
https://www.passagemaker.com/cruiser-re ... s-round-up

There are some drawbacks, and in our size range (of engine) the inboard diesel most likely wins on fuel economy. This is not really a cost concern so much as a range issue.

Researching the right size outboard engine for a displacement hull proved inconclusive for me. Different "sources" offer different formulas. The best data I found for evaluation was anecdotal experience. In our own forums, we've had people able to move their boats at hull speed around the marina with sub-10hp motors. Its probably a different story in a seaway. There are sailboat owners who are satisfied with 10hp-15hp, and while their motor is technically an "auxiliary," any honest sailor will agree that most sailboats operate under power most of the time. (Long distance cruisers excepted of course)

I considered a 20hp and a 30hp before settling on the Suzuki 25hp. Everyone has their brand, but I like Suzuki. I was impressed with the 2.5hp I bought to tow my boat with (and subsequently traded FOR the boat). Yamaha is great, but I can't find them available online except from untrustworthy websites (based in SE Asia), and buying full retail adds to the ticket price. The 25hp and 30hp 2021 Suzuki have the same bore, stroke, gear ratio etc and both weigh 158lbs (20" shaft). I suspect it's the same motor with a different EFI computer, and the 30hp lists a higher WOT RPM. Both put out a paltry 14 amps. The 20HP is probably enough to push the boat, but it is a 2 cylinder versus 3 for the 25hp, and the alternator yields a dismal 9 amps. Moving to a 40hp for higher amperage (19 amps) increases weight to 230lbs. This is not a real problem for the boat, especially the Deluxe, but it puts added strain on the mounting system. Also, it increases cost.

I agree that for those who have a mechanically sound inboard, its probably not wise to swap. For those of us not fortunate enough to have that situation, the outboard seems like a good choice. Plus it frees up the motor well for nerds who still want to try an electric option for the inboard shaft

[DesertAlbin736]

The "other" outboard powered cruiser worth talking about is the C-Dory. There are various size models but the 25 is closest comp to A25. These are planing boats & very sea worthy. Eminently trailerable but also quite expensive, from mid 5 figure to pushing close to 6 figure. Personally I'm not crazy about the layout except for the open stern cockpit which could be shaded with a bimini. The layout is similar to Nordic & Ranger tugs, with a low ceiling 'cave' V berth up forward & the salon with just driver seat, dinette, galley & head but not the kind of sitting arrangement like the A25 nor an aft cabin for storage or guest privacy. Great visibility though. BUT, it can go fast with 3 GPH fuel burn at 15 knots which admittedly can be fun.

https://vimeo.com/233678642

[NickScheuer]

The outboard planing motor cruiser I like best is the Blue Jacket 25 designed and built by Tom Lathrop. What really impresses me is a top speed in the low 20's MPH powered by a mere 50hp. That is quite a lot less than similar speed for other designs like C-Dory and Rosborough requiring 100hp or more. Weight is one factor, with Blue Jacket displacement being just 3000lbs. Another factor is a bottom configuration which is simply easier to get on plane at a reasonably low speed while keeping hull trim optimum throughout the entire speed range. Said bottom is not a Deep-V, which is another plus resulting in a very mild wake. As a former sailor (65 years) I especially dislike the wakes pushed up by typical Deep-V hulls.