Evinrude 3 vs 4 cylinder mpg?

[seahorse5]

Re: Evinrude 3 vs 4 cylinder mpg?

. The prop is the largest diameter that the motor will take, and the pitch seems correct in that the top RPM is right around 5700 RPM, give or take
.

That motor was designed with a 5500 rpm redline so your 5700 rpm is overrevving the motor. first you must make sure that the tachometer is accurate at that rpm range, then reprop to get the revs between 5000 and 5500 with a normal load.

The 65 should burn about 7 gallons per hour at full speed and about 4-5gph at an average cruise.

Either your measurements and calculations are a mile off or someone who worked on the motor does not know how to check for carb problems, pump diaphragm leakage, or someother problem with the motor.

 

[jay_merrill]

Re: Evinrude 3 vs 4 cylinder mpg?

If your friend's motor is loading up at idle, its probably running rich. Check the exhaust relief holes in the back of the midsection - my guess is that you'll see alot of "soot" there.

One more thing ... what is the transom height on your friend's boat? As a 16' boat built in the 60s, I wouldn't be surprised if it is 15". There is a 15" shaft length model of the '72 65hp OMC and probably is on the '73 model, but there weren't many of them built. That being the case, I'll take a WAG that your friend's motor is a 20" shaft length.

If it is and the transom height is 15", your friend is dragging a lot of motor around, below the water line. That might explain why his boat os so slow, given the boat size and hp rating.



???

 

[mfgniagara]

Re: Evinrude 3 vs 4 cylinder mpg?

No noticeable soot at all. I'm not sure if it loads up or just idles too low.
The transom on both his and mine are 20" tall, and the motors match. His motor is mounted with the anti cavitation plate about 1/2" above the bottom of the hull. I mounted the motor, he had it bolted up with the motor bracket resting on the transom, now it sits about 1" above. I raised it in hopes of improving the mileage a bit, but no real difference. It does handle better now though.
He took it upon himself the other day to add one of those hydrofoil fins to the motor, all that seams to have done is to cut top speed down to about 21 mph and create a huge wake behind the boat. It does pop up on plane faster but all other aspects of the boat are hindered. I somehow figure that will also hurt the mileage even more.
Something I noticed the other day while running along side his boat is that his rides far lower in the water than does mine while under power, yet his has at least 3" more freeboard than mine at rest. Trim position or pin position makes little difference. On take off, his boat sinks deep in the water, even when on plane. It's like the motor digs a hole in the water and boat settles in it. While following behind him, the top of his stern is actually below the water line. Mine never sinks down like that on launch, it rises up and stays up. If riding along side, there is air under his hull about 2/3rds the length of his boat, about the same as mine. I'm not sure I understand what's causing this difference in ride, especially since my boat is heavier with more gear onboard and a heavier motor.

 

[ezmobee]

Re: Evinrude 3 vs 4 cylinder mpg?

Hmmm, odd. Well if he's plowing......that'll do it! Now to figure out why he's plowing????

 

[jay_merrill]

Re: Evinrude 3 vs 4 cylinder mpg?

You mentioned a 22 mile round trip on your river, in which you burn about 6 gallons of gas and your friend burns 12 gallons of gas. What power settings are each of you using on this run? Are you at less than WOT and is he running at WOT on those runs?

My point in asking is that I know My 65hp Johnson burns a lot more fuel at WOT, than it does at lesser power settings. There also isn't much difference in speed between WOT and a few hundred rpm under WOT.

I am propped to achieve WOT at 5,100 rpm, which is 400 rpm under the top of my recommended WOT range (4,500 - 5,500). Running at about 4,300 rpm gives me about 25 mph, while the extra 800 rpm only gives me about another 4 mph. I rarely run the motor that way, because all it does is to make a lot of noise and burn more fuel.

BTW, I did a couple of searches on this topic and ended up running across a thread right here at iboats that was sort of interesting. One of the members here has an MFG Westfield with an older V4 on it. The thread was about a conversion that he did to his mid sixties 60hp V4, by putting an 80hp powerhead on it. The thing that I noticed which I thought keyed into this issue, is that his boat ran at the same speed at WOT as your friends, prior to the powerhead change - he was getting 28 mph with a WOT 60hp V4. What this leads me to believe, is that the boat is heavy for its length. If it is, maybe your friend is running his motor at high power setting all of the time and is paying a price in fuel consumption.



???

 

[mfgniagara]

Re: Evinrude 3 vs 4 cylinder mpg?

You mentioned a 22 mile round trip on your river, in which you burn about 6 gallons of gas and your friend burns 12 gallons of gas. What power settings are each of you using on this run? Are you at less than WOT and is he running at WOT on those runs?

My point in asking is that I know My 65hp Johnson burns a lot more fuel at WOT, than it does at lesser power settings. There also isn't much difference in speed between WOT and a few hundred rpm under WOT.

I am propped to achieve WOT at 5,100 rpm, which is 400 rpm under the top of my recommended WOT range (4,500 - 5,500). Running at about 4,300 rpm gives me about 25 mph, while the extra 800 rpm only gives me about another 4 mph. I rarely run the motor that way, because all it does is to make a lot of noise and burn more fuel.

BTW, I did a couple of searches on this topic and ended up running across a thread right here at iboats that was sort of interesting. One of the members here has an MFG Westfield with an older V4 on it. The thread was about a conversion that he did to his mid sixties 60hp V4, by putting an 80hp powerhead on it. The thing that I noticed which I thought keyed into this issue, is that his boat ran at the same speed at WOT as your friends, prior to the powerhead change - he was getting 28 mph with a WOT 60hp V4. What this leads me to believe, is that the boat is heavy for its length. If it is, maybe your friend is running his motor at high power setting all of the time and is paying a price in fuel consumption.
???

My V4 is a bit over powered for my boat, so I don't push it very hard. My V4 is propped to run 5800 RPM max, I run at about 4500 on the river tops. His 65 is propped to turn about 5700 RPM max, but we run it about 4500 or so simply because it sounds better there and not much is gained above that RPM. My boat will gain a lot more above 4500, but I've always been a bit leery of it being rated 10hp higher than the boat is rated for.
Its an old boat and I just don't push it very hard.
His boat basically requires WOT to maintain full speed, even though his is the lighter loaded boat. These boats are not heavy at all for their size, if anything I'd say their on the light side, which is what perplexes me even more. The only real difference between my hull and his is cosmetic, his has all those extra snaps riveted to the gunwales and his still has it's original bimini top which attaches to the windshield frame up front. Mine has a new freestanding bimini top with a vertical riser section that snaps to the top of the windshield and to the leading edge of the bimini top. My top is 80" above the deck, his is only as high as his windshield with a slight rise rearward.

I don't doubt that me being at about 1/3rd throttle and he at WOT has a lot to do with the MPG, but I wouldn't expect it to be that drastic?

On my boat, if I run WOT, I gain about 8 mph over my 4500 RPM cruising speed. On his, he gains maybe 2 MPH, and only uses more fuel. Once his is on plane, it's as good as it gets, regardless of the RPM or current. Now that he added the hydrofoil, the speed dropped off even more and the boat handles bad and makes a wake that looks like a tanker went past.

Something that I don't understand is how low his boat rides compared to the surrounding water even though it's clearly on plane. His boat rides at an attitude just a bit bow high above level, and on plane at 25 or so MPH 2/3rds of the keel is visible. When I'm in the boat, it feels more like it's plowing the water but when observing from along side, I see its well on plane.
The part I don't get is how it can sink down that low in the water and still be on plane. My boat sort of hops up and takes off, partly since I have power trim and can force it to jump up faster but even when trimmed way in, my boat is way up above the water. I feel like I'm 6' above the water in my boat even though I sit lower at the helm, in his, it feels like I'm sitting in a hole of water when I look to the left or right. In his, I can touch the water from the driver's seat, but in mine it's way out of reach down below me.

 

[jay_merrill]

Re: Evinrude 3 vs 4 cylinder mpg?

You have conflicting information here. In one place, you say he is propped for WOT at 5,700, but he only runs the boat at 4,500 rpm. In another place, you say he runs at WOt all of the time.

The difference between 4,500 with the butterflies partially open and 5,700 with the butterflies wide open, could be substantial.



???

 

[mfgniagara]

Re: Evinrude 3 vs 4 cylinder mpg?

At WOT the motor will achieve 5700 RPM give or take a hundred RPM depending on load I guess. It runs best around 4500, mainly since there's no real speed or performance gain above that RPM. The motor just seems to get louder and make a bigger wake, but the boat gains little to no speed. This is more noticeable when running against the wind and/or tide.

The engine revs with the added throttle and the prop obviously is working harder since the wake gets huge, but the boat don't gain but a mile or two per hour in speed and fuel consumption gets even worse.

If cruising along at 4500 RPM, doing about 22 mph, increasing the throttle to WOT doesn't bog the motor or anything, it gains RPM fine, it just don't seem to relate in MPH. The motor is trimmed in the second from the last hole right now, I tried the last hole but it pushes the bow down too far. Going to the third hole raises the bow and makes the hull slap on almost any wave or wake since its basically a flat bottom at the stern.

My buddy don't seem to really feel there's an issue, just that it uses a lot of gas. He's apparently used to this kind of mileage.
He changed the hydrofoil again today, this one is flatter than the first one he bought, and it drags the speed down even more but it pushes the stern up a bit higher on plane, but still not to where mine rides.
It's really a strange feeling in that when your at rest, the boat sits normal in the water with plenty of freeboard, then when you hit the throttle the boat digs in and rides almost below the water level.
A sudden stop brings a surge of water over the stern into the splashwell at times too. Mine has never had any water come in that way. Mine makes very little wake, even on plane. My wake is larger when at minimum throttle just putting along. His wake gets bigger with speed. On his boat, there are two pronounced wake trails, one on each side, two almost rooster tails coming from each side of the motor down low. I at first thought that this was being caused by the anti cavitation plate being too low, which is why we originally raised the motor a bolt hole, but the water comes out of the prop wash, not from the hull or lower unit area. The water that's shooting upward don't start till about 18" behind the prop if you watch it while on plane.
Something else I've noticed is that when you gun the engine hard, the boat drops down so low that the water level is nearly flush with the top of the transom, and it stays there as the boat accelerates. The water level drops a bit but the boat don't seem to rise back up, more that the prop just pumps that water away. It's more than a little unnerving to ride around in 50 degree water knowing that your riding below the water level or so close to swamping.
I think the ticket is to get the boat up out of the water somehow, I'm just not sure what is causing this. So far he's tried several props, including one which a local shop custom cupped, two hydrofoils, motor height, and tilt position have all been tried with nothing making any noticeable change. The flat hydrofoil did raise the boat a few inches but it made the wake worse and took off about 6 mph or so, raising the motor was only to put it where it should have been in the first place, and the prop changes only made RPM changes which were either too high or too low.
I think I've got an idea of what's going on with the low idle or stalling, when you come to a stop, the wake covers the exhaust relief ports, this is when it usually dies out, but it don't explain why it loads up after idling for a long time. A lot of that may just be normal for a two stroke.

The one very noticeable difference between his 65hp triple and my 110 V4 is that mine is WAY quieter, you can hold a conversation with the motor running in my boat, but that 65hp is just plain loud. Mine seems to put out a more mellow exhaust note when running, especially at idle, his sounds more like a raspy dirt bike running.

 

[JBF 1962]

Re: Evinrude 3 vs 4 cylinder mpg?

My old 1975 Evinrude 70 triple was a huge pig on gas. Turned out the carbs were worn out in that the area where the butterflies pivot, a gap was worn. After i sold it, the new owner replaced them and it's been getting amazing fuel economy ever since

 

[Willyclay]

Re: Evinrude 3 vs 4 cylinder mpg?

Here's a link to fiberglassics.com website with some info on the MFG's;

http://www.fiberglassics.com/library/File:Mfgb65010.jpg

The brochure does mention this model having foam floatation under the floor. Good luck!

 

[mfgniagara]

Re: Evinrude 3 vs 4 cylinder mpg?

Here's a link to fiberglassics.com website with some info on the MFG's;

http://www.fiberglassics.com/library/File:Mfgb65010.jpg

The brochure does mention this model having foam flotation under the floor. Good luck!

If they put foam in the floor, it has to be up front in the very tip of the deck, a raised section under the bow deck. I've checked several of these from 1965 and '66 and have never seen any foam below the main floor. These have a dual drain plug, one that drains the above floor area, and one that drains the trapped air space below the deck. I've got an inspection camera from Snap-On and have stuck that thing both in the drain hole and down through the factory seat mounting holes and there's nothing down there but fiberglass stringers.
Neither boat felt heavy, both were garage kept since day one, his was just a bit more drilled and screwed with extra snaps and things. Mine has no holes drilled anywhere. The only add on I have is a custom panel blocking off the under bow storage to keep things in place in rough water. I can lift the bow of either boat off the trailer pretty easy, they're very light boats. Mine is heavier having more junk in it. His is pretty stripped other than all the fuel tanks.
I think having to carry all that fuel is the biggest headache, more so than the fuel bill. It's a small boat and having three loose fuel tanks in the boat to trip over is a real pain.

As to the carbs, he's had several sets of carbs on that motor, he has about four sets, if something happens to one set, he swaps out a fresh rebuilt set while he has the others fixed. His garage looks like a 65hp graveyard, he's had at least a half dozen of these motors over the years, both electric shift and later models. He's pretty resigned to the fact that it burns as much fuel as it can carry in a day. If I were him, and were using the boat to make money, I'd find something easier on fuel. But he's stuck on that hull. Like me, he's had dozens of MFG boats, and always has another lined up as the next boat. My current boat is my first of this model but he's had many. I've also got two others, one of which I just picked up today. The latest is a later model Westfield which came to me with an Electric shift 55hp Evinrude triple. Having no intention of running that motor, it's already hanging on the hook in the garage. I'll be hanging a 55hp Johnson twin in its place. This latest boat could pass for brand new, a real time machine from what I've seen so far.

 

[jay_merrill]

Re: Evinrude 3 vs 4 cylinder mpg?

At this point, I don't know what to tell you except for one thing - he's burning way more fuel than that motor should. Twelve gallons of gas to run 22 miles is about twice what he should be going through, based on the information that you have given.



???

 

[mfgniagara]

Re: Evinrude 3 vs 4 cylinder mpg?

I think the problem solved itself this morning, he went out early before daybreak to get bait, said it was hard to start and lacked power the whole trip. He said he couldn't get over 3900 RPM out of it.
When he got here with it, I did the basic checks, it sounded like it had a miss to me, so I checked compression, there was none in the top cylinder. When I probed the cylinder I could see that the piston wasn't moving and stuck up top, when I pushed on it, it slid back. When it did, I heard something drop, a magnet down the plug hole retrieved a rod bolt and a half dozen roller bearings.
He's digging up a spare motor to hang for tomorrow. I pulled the head, the cylinder is perfect, the rod looks fine but twisted now, both rod bolts were in the ports. Neither look damaged. It looks as if the rod bolts just pulled out or came unbolted. The crank also looks fine so far. Either way it's not worth the rebuild unless he's got some used parts from past motors. The pan was full of water and he said he bailed on the throttle once yesterday and took a lot water over the motor and splash tray.
He's got another 65 which needs only some parts swapped over to it. I think it's electronics were on this motor. We'll see how the next motor does. He wanted to hang the later model 70hp I just bought but that's marked for my other boat. He's got about 20 or so 65 hp motors, he's been buying up everyone he finds for parts for three years now.
One thing I did notice is that the prop he's running is so large that it barely clears the anti-cavitation plate, the prop on the 70hp I bought has an inch between the plate and the blades. I think the prop on the 70hp I have is only a 13x15P, he's running a 13.5 or 13 3/4" x 17 or 18P. If the prop was another 1/8" larger in diameter it would hit the housing. On all of my motors, there's a good bit of clearance between the prop and the lower unit itself. On his, it's only a about 1/6" away from hitting the bottom of the anti-cavitation plate.
He keeps track of motor usage with an hour gauge, he figures this motor has about 1100 hours on it since he hung it. According to him it's gone the farthest of any of the motors he's hung on it. Keep in mind he runs it almost every day of the year so long as it's not frozen over. It only gets Jan and Feb off each year and a handful of odd days here and there.
The cylinders still look good, there's still crosshatch visible and no scoring, and no carbon build up. This one was apparently rebuilt before as the pistons are marked .030 on top. I'd be tempted to throw a bearing and rod in this and see what happens if all the other rods and bearings look good. It almost looks to me like the rod bolts fell out or the threads failed. He said it never knocked, just lacked power. It may well have come apart and left the rod up against the head either on shut down or start up. Not even the spark plug was damaged.

I can't wait to see the mileage with another motor. He don't seem to think it'll be any different, as this is his third or fourth one of these motors in several years.

 

[Willyclay]

Re: Evinrude 3 vs 4 cylinder mpg?

It may well have come apart and left the rod up against the head either on shut down or start up. Not even the spark plug was damaged.

I would have never thought this was possible! Agree with you on the prop size. Once he gets another motor bolted on, he should do some serious prop testing with a tach and GPS.

 

[mfgniagara]

Re: Evinrude 3 vs 4 cylinder mpg?

I guess sometimes you just get lucky as to how a rod breaks?

The new motor is on and running, but the prop situation is still not resolved. The prop from the other motor doesn't seem to work on this motor. While this motor has good compression, and seems to run great, it won't achieve more than 3600 RPM with the same prop that was on the last motor. It's a bit better with the 13 1/2" x 15p prop but still it only hits 4250 RPM. He's looking for a smaller prop to try.
What gets me is that this motor is the same model as the last, only with a year older power head installed. Its almost as if the lower unit has a different gear ratio.
The weather has turned colder here so I'm looking at putting my boat up for the winter, he'll run his all winter or till the point that the water ways ice over. If he gets his figured out again, that'll be the boat we use till the weather warms up here again. I just hope this one isn't as bad on fuel.
I'm a bit leery about this motor wanting a smaller prop, I'd really have thought that the old prop would have worked fine on this motor.
The lower unit feels good, and it's all resealed with a new water pump.

 

[Chris1956]

Re: Evinrude 3 vs 4 cylinder mpg?

When you get the replacement motor sorted out, I had another thought. From your description, it sounds like the boat is plowing water. You might remove the whale tail and adjust the trim for max speed. Fuel economy will follow.

 

[mfgniagara]

Re: Evinrude 3 vs 4 cylinder mpg?

I don't think the new motor is 100%, he ended up with a 14x11P prop, and a top speed of about 21 mph. No where near what the last motor was capable of with a much larger prop, (13x15). It shows 5550 WOT with the 14x11P prop. The dealer said that the prop he's running now is more common on big pontoon boats, not a 17' runabout.
Fuel usage is better, but the boat is slow and hard to get on plane. The engine has good compression but has two head gaskets installed and a decal saying that some recall was done to allow the use of regular gas. It only gets on plane at the very top of the RPM range, over 4500 RPM, without the hydrofoil or whale tail. With it, it climbs on plane around 2700 RPM with this motor.

He wants me to swap motors with him to see how the two boats react but I'm just not messing with my boat. It runs too good the way it is.

I think this motor has issues, not sure where but he's already swapped the carbs from the old motor, swapped in the stator and harness, and tried two different lower units. At this point, I give up, its his problem. One dealer, as well as the prop shop said they think it's a matter of not having enough horsepower and that the motor is working too hard to move the boat.
I'd buy that but I just bought an MFG Westfield, which is basically the same boat a foot shorter and a few inches narrower, that runs great with a 50hp Johnson on it, it runs all day on a 6 gallon tank and does nearly 30 mph with two guys onboard. That boat is running 20hp under it's max hp.