Update #1: Significant Fuel Consumption Difference

[rodbolt17]

it is simple.
what to crocs eat? meat.
what do sharks eat? meat.
what am I made of? meat.
solution? stay out of the water.
if I am swimming in saltwater there has been a serious issue with da boat.
if I am laying on the beach in the sun? I have had a few to many and please drag my tail into the shade.

[boscoe99]

They are becoming a bit worrisome here of late. They usually take unsuspecting tourists, but are getting a few locals.

However in the tropics, when the odd tourist asks at a lagoon or beach whether it is safe from sharks to swim, they are usually assured that there are none.

Now, Australians can be of few words. If you get one willing to talk a bit more he would probably say that there used to be sharks there, but the crocodiles cleaned them out.

The tourists might want to be on the look out for Mr. Cocodrillo.

[zenoahphobic]

Sharks aren’t too terribly worrisome.
Unless you live in Australia....little bigger and more frequent there. Oh and the box jellies too.

They are becoming a bit worrisome here of late. They usually take unsuspecting tourists, but are getting a few locals.

However in the tropics, when the odd tourist asks at a lagoon or beach whether it is safe from sharks to swim, they are usually assured that there are none.

Now, Australians can be of few words. If you get one willing to talk a bit more he would probably say that there used to be sharks there, but the crocodiles cleaned them out.

[boscoe99]

what I am trying to say is you can run both up,take a screen shot or a recording,stop and switch the laptop to the other motor. run them up again and repeat.

Too bad that YDIS does not have the capability to display data from multiple motors at the same time. Maybe flagging motors when they are not within a certain range of each other. Say they are at the same RPM and manifold pressure but the TPS or fuel flow values don't agree as maybe they might.

[pstephens46]

Sharks aren’t too terribly worrisome.
Unless you live in Australia....little bigger and more frequent there. Oh and the box jellies too.

[zenoahphobic]

Hard enough to swim back there, hold on with one hand, and unwrap 30 yards of fishing line from the prop. All the while, the dumbass responsible, is standing at the back of the boat still holding the rod.

Imagine cotter pin and nut removal, removing 13lb prop and not dropping a damn thing. And then you are only halfway completed.

I was thinking dual engined boats by definition are larger boats, so if a "gang plank" is slipped up the sides, or such, the extra human weight could be accommodated.
Having some securing harness on a fully tilted up engine, and a proper net or bag hung across underneath from it to hold tools or catch components, would be far safer than any floating in the water behind attempts.
I've been looking for simple solutions to get to the back of my boat whilst it is attached to my jetty, to do for example, the simplest tasks like undoing the bung (raised above water on float) let alone water pump etc without it having huge degrees of difficulties. Working on anything on the outside, I find you need to be fully "bonded" with the boat. I hate to have to always require to pull the boat out of the water.

[rodbolt17]

what I am trying to say is you can run both up,take a screen shot or a recording,stop and switch the laptop to the other motor. run them up again and repeat.

[pstephens46]

yep those that know, will make it back to port after many hours without hurting the good motor
some will try running on plane.

out on the water it could be difficult to swap props unless it is dead calm and someone likes to swim with the sharks

Hard enough to swim back there, hold on with one hand, and unwrap 30 yards of fishing line from the prop. All the while, the dumbass responsible, is standing at the back of the boat still holding the rod.

Imagine cotter pin and nut removal, removing 13lb prop and not dropping a damn thing. And then you are only halfway completed.

[99yam40]

yep those that know, will make it back to port after many hours without hurting the good motor
some will try running on plane.

out on the water it could be difficult to swap props unless it is dead calm and someone likes to swim with the sharks

[zenoahphobic]

why would anyone run a twin engine boat on one motor at WOT?

I guess it has been thought by almost everyone at some point contemplating having dual engines,
One should be able to run the boat on one engine, at full power and maximum possible speed, in the event one fails; an additional (darn good one) safety factor.
But as is always pointed out, the prop for dual would not allow either one to do so.
The prudent owner would thus have a set of appropriately tested alternative props to use in this situation.
One would also need appropriate means to be able to swap props outboard and perhaps at sea.

[zenoahphobic]

Running a dual engined boat on a single engine will in all likelihood produce different results, even to the differences you have found without anything really wrong with any particular engine.
This is because there are differences in how each engine relates to the boat; for example they both rotate in the same direction although the props run opposite to each other.
Moreover the boat probably has not been setup to optimise each individual engine on their own (no one really does). Simply the differences could even be attributed to the differences between propellers.
I would not worry about short term WOT at any revs. This nonsense you hear is to do with possible long term running damage. It is nonsense because say running at half throttle should therefore produce what revs?. Or for any other throttle position? Just think if you were to put a smaller carburettor on the same engine, WOT would now be equivalent to less than WOT with the previous carburettors!
So there is room to optimise each engine; running the existing propellers is meaningless. It's a catch22 to do this. A very difficult thing to balance them!
All that said, I suspect the problem lies in the boat. Things like weight distribution, damage to the hull etc. etc.
I would critically look at what might have changed.

[pstephens46]

As a group we do this often. Just banter back and forth while waiting on the OP to return with more info. Been slow around here. No one intended to insult or cause you to leave.

[boscoe99]

I guess a couple of you are having fun at my expense, yuk it up... It was done under the supervision of a certified mechanic and for a very short duration. It amazes me the assumptions Internet folks make without knowing anything about somebody. There is a big difference in having knowledge and using it to help someone, as opposed to having or thinking one has knowledge and poking fun at someone trying to learn. Your parents/teachers should have taught you that. If you have something constructive to offer please do so. I get enough chuckles at my own ignorance on this issue without your help.

We are not laughing at you we are laughing with you. Oh, but you are not laughing.

Seriously though, we are trying to make a point. If one of two motors is run at wide open throttle without a propeller change there is a risk of doing serious damage to the motor. The motor is being lugged. It is way over propped. Yamaha wants the motor to be able to turn at or near 6000 RPM when it is at wide open throttle. By your own comment the motor could only turn 4500 RPM or so. Not good for the motor. Furthermore, it is not a valid test of anything.

Same with running a motor at wide open throttle when in neutral. It cannot validate anything. It can only possibly, repeat possibly, do harm to the motor.

[bjd76]

I guess a couple of you are having fun at my expense, yuk it up... It was done under the supervision of a certified mechanic and for a very short duration. It amazes me the assumptions Internet folks make without knowing anything about somebody. There is a big difference in having knowledge and using it to help someone, as opposed to having or thinking one has knowledge and poking fun at someone trying to learn. Your parents/teachers should have taught you that. If you have something constructive to offer please do so. I get enough chuckles at my own ignorance on this issue without your help.

[rodbolt17]

hey
I wear a belt everyday.
I carry a hankerchef everyday.
when I wear a ball cap I know how the brim works.
I also know how to PROPERLY test an engine.
it actually involves eyeballing it at its failure RPM and load.