Slow to get out of hole and WOT RPM too high

[roffey]

I have a little tin fishing boat with a 9.9 on the back. It would take forever to plane and when it did it was revving just like you say. At first I thought it was weeds, Turns out it was a spun prop. Once I picked up a little vegetation the prop would spin. One new or new to me prop and all is good once more... I think the motor being mounted to high seemed like a winner as well. Easy to check, just pull the boat and see where the anti-ventilation plate sits?

It will be interesting to see what the cause and solution is...

 

[Sea Rider]

Turns out it was a spun prop. I think the motor being mounted to high seemed like a winner as well.

Besides having already a spun hub, the only way a motor sitting at 90 deg will overrev badly will happen when water flow skims close or under the AV plate, too poor water bed level for prop blades to achieve top prop thrust when at plane. In that case will need to lower the motor down till the orver revving has ceased. If can't lower the motor no more due to a motor/transom height mismatch will need to shave the middle transom down for the prop to bite at a higher water bed level.

Happy Boating

 

[JimS123]

In my personal experience I have seen transoms that varied in height from 15" to 17". Also, my statistics indicate that motor leg heights are all at 17.5 inches. I'm sure that the manufacturers design them that way to ensure no ventilation or cavitation, with the dimension set for the worst possible case.

Now, if someone puts a short shaft on a long shaft boat, that's yet another issue. And of course, my caveat is that I'm also sure that somewhere some manufacturer made a leg or a transom that didn't conform to normal practice.

 

[Sea Rider]

In the golden boating era Normal Practice was probably such with respect to high end HP motors, in current portable clamp screw ones it's like what the prop manufcturer wants to put regarding the prop diameter. With outboards happens same, doesn't matter if being S or L shafts models between different motor brands.

A Yam S shaft motor that woks spot on on a S transom will not perform same with other brand motors as both have different lower leg plates heights differences which you guys don't give a you know what and prefer to play with the cast on stone AV plate even or close to the boats bottom which Only corresponds to *Dry Installations*..

Besides the transom height, there are 2 other parameters that nobody has accounted for for best transom/lower leg hotspot matchto to achieve top prop thrust....

Happy Boating

 

[JimS123]

In the golden boating era Normal Practice was probably such with respect to high end HP motors,


both have different lower leg plates heights differences

In the golden era there were NO high HP motors. Grandpa and Dad came home from the war, bought a little boat and motor and took the family out for a ride. There was no concern for speed or performance. It was just a family thing.

We may have to agree to disagree. This is our big bone of contention. Data would indicate that the lower leg dimensions are all the same. The difference is where the manufacturers suggest where to put them on the boat.

Outboards were invented and developed for the masses in America. (Ole Evinrude was my hero......LOL) I realize that the Japanese have a different theory. I spent many years consulting with a Japanese company that licensed US technology. I never met one of my associates that owned a boat.

 

[Sea Rider]

The motors manufacturers doesn't suggest where to put them on the boat, just suggest as Pontius washed his hands where the AV plate must be set in relationship to the aft boat's bottom. If any of you guys would have read every Motor Owner's brands Manuals would realize that all of them uses the exact same deep V hull shape for all motor brands installations as a refercence which ain't so as there's lots of variable hull shapes found now a days That's why to each boat brand its brand installation, as each is unique, can't throw them all in same sack and pretend for all to work excatly same.

There's no such big bone contention, the issue is that you guys specially the one who likes driving his crazy watercraft out of the water wants us all to follow the parameters that works fine for his Merc motors, clamp screw motors performs diferently to bolt on motors wjen running at speed.

Will discuss that contention going on for years now with proven pics when my summary is finished. It's not about who's right, who's wrong, just want IBoat guys and new boaters as well to change the old way of thinking and dial modern data parameters to be aware of what's going on at the front of newer motors if plan owning them in the near future...

Happy Boating

 

[JimS123]

The motors manufacturers doesn't suggest where to put them on the boat, just suggest where the AV plate must be set in relationship to the aft boat's bottom.

If any of you guys would have read every Motor Owner's brands Manuals would realize that all of them uses the exact same deep V hull shape for all motor brands installations as a refercence which ain't so as there's lots of variable hull shapes found now a days That's why to each boat brand its brand installation, as each is unique, can't throw them all in same sack and pretend for all to work excatly same.

My pile of owner's manuals covering many manufacturers all say where to mount the AV plate. They all say the same thing.....EXCEPT for Tohatsu. They are the odd man out. Their recommendations are different from the rest.

I can say that because I DID read the manuals. I concede that my collection covers only 69 motors, so I probably missed a lot.

AV plates weren't even invented before the late 1940's, so my guess is that Ole didn't know any better. It must have been Ralph or more likely Carl that did the Engineering.

Its also my thought that the little clamp on motors probably don't go on deep-v hulls anyway.

Seems like the horse is dead. I'm going to bury him and go boating.

 

[WesNewell]

Wrong on all counts. Page 85 of my mercury manual shows a picture of how to mount the engine for both single and dual engine installation. It clearly shows the av plate even with the bottom of the boat. You are right about one thing. Each hull type requires consideration for different mount heights. A deep V hull design should have the engine mounted higher than a flat hull type.
Whether clamp on or bolt on makes no dfference with the exception that most bolt on engine are lower hp where perfomances won't differ much no matter how high or low you mount it.

 

[Faztbullet]

Will discuss that contention going on for years now with proven pics when my summary is finished. It's not about who's right, who's wrong, just want IBoat guys and new boaters as well to change the old way of thinking and dial modern data parameters to be aware of what's going on at the front of newer motors if plan owning them in the near future...​

For you to have a summary that is ever close to having any correct information ..you need to know and understand how lower unit/ props/ lower unit shapes and hull designs work, not just your ideas of how you think they work. If you really want to know why Tohatsu runs their engines deeper look at the lower unit...and its not the AV plate or splash plate heights.

 

[Faztbullet]

A pic of prop and numbers would help as a 225/250 should spin a 19 pitch with lil effort. Those are good riding boats...

 

[JimS123]

Tohatsu runs their engines deeper look at the lower unit...and its not the AV plate or splash plate heights.

As Jerry once said "Now we're gettin' somewhere!"

I went out to the boathouse where I have 2 Tohatsus sitting next to 2 Mercs, plus a bunch of 'Rudes and so on. The difference didn't just jump out at me. Could you please elaborate?

 

[Sea Rider]

For you to have a summary that is ever close to having any correct information ..you need to know and understand how lower unit/ props/ lower unit shapes and hull designs work, not just your ideas of how you think they work.

Hey Fazt, almost flipped my chair laughing out loud reading your fantasic new information, as always love being the you know all King of this Prop section due to your extremely oversized Ego. Have not posted anything yet and you inmediately come up with your usual institutionalized BS you love to post answering mine..

Rest assured, I will make you swallow your own words regarding the height importance of both mentioned lower leg plates. which you don't know a whiny bit about how they interact with water. For the moment can keep clowning boating with 95% of the hull out of water, you're only 5% away to end sitting on the cowl's top..

Happy Boating

 

[Faztbullet]

I went out to the boathouse where I have 2 Tohatsus sitting next to 2 Mercs, plus a bunch of 'Rudes and so on. The difference didn't just jump out at me. Could you please elaborate?​

Look right above the prop on AV plate..

Rest assured, I will make you swallow your own words regarding the height importance of both mentioned lower leg plates. which you don't know a whiny bit about how they interact with water​

This is where your wrong ducky boy...the upper plate is NOTHING but a water deflector to keep water spray from coming upper bottom of engine..it has NOTHING to due with operation of motor as it is above water on plane. The lower is AV plate which everyone knows it purpose but you seem confused about.Your summary may have some substance with Tohatsu engines but your BS and ideas opinions do not apply to other engines.

For the moment can keep clowning boating with 95% of the hull out of water, you're only 5% away to end sitting on the cowl's top..​

Yep that the way 90% of the USA boaters run....When in doubt ..Trim it out. They do know how to use trim and its not 90° parallel. That why my set-ups are faster as there is less wetted surface and less lower unit drag in water. Always been able to set a hull up without a "transom modification" by adjusting height,setback,wedges and prop styles. You need to study real good and get MFG to change their manuals before you post your "summary"

 

[JimS123]

Look right above the prop on AV plate..

Thanks!!! OK, now I get it. Had to stand on my head to see. Never would have thought to look there.

All I can say is: "What were they thinking?". As I have said before, outboard motors were an American invention and that's where the innovation has progressed, and that's where the biggest customer base is. My 45 years with patents has shown that much of the new stuff ain't what its cracked up to be. Surely the Japanese have done an exemplary job at copying US motors, but their new ideas maybe aren't based on actual practical use.

Just glad I have an ample supply of 'Rude and Merc dealers in town.

 

[jimmbo]

I can't Adjust the Height on Mine, That Enertia can hold Most of the Boat out of the Water

 

[Faztbullet]

Hey Jimbo ..that the way a I/O should run but most of the dealers do not set the trim limit or prop to customers use. If you could find a X drive upper(3" shorter) it would raise you X dimension so prop shaft would be at about 5" below pad. and get it up on the last part of pad. Would also drop the nose a tad.