Not getting a desired speed

[JimS123]

Yupper, no one reads the manual, that's why only a few know what they are doing....LOL.

From the 1970 Evinrude Triumph Owner's manual (installation instructions): (50 freakin years ago)

• mount the motor in the upper holes
• Select a propeller that will allow the motor to run at WOT in the upper half of the spec range.
• with the proper prop, raise the motor one notch at a time until the optimum performance is achieved (i.e, cavitation, top speed, increase in engine speed, yada, yada, yada (abbreviated and paraphrased)

That manual was from my second new store bought motor, and the first with an adjustable transom bracket.. The dealer had been in bizness since 1946. The 1950's were the the golden age of trailer boats. He not only told me where to mount the motor but he showed me by going along for trial runs. His Son now owns the business and the Grandson is the chief mechanic, so we never needed no internet.

Weekend boaters don't know what to do, nor do they care. It's just a diversion. But for those that care, knowing proper motor height was well known eons ago, because we had good mentors.

Just yesterday my county announced that all county run boat launching ramps are now open. All my gas tanks are full, batteries charged up to 12.7, hulls polished and all we need is to have it stop raining. No problem social distancing in the mile wide Niagara River

 

[jimmbo]

Deleted as it may have taken the Thread off on a Tangent

 

[Faztbullet]

Sea your so full of crap its ridiculous... Maybe if YOU read the manuals,prop theory and basics of engine operation people wouldn't have to correct your misinformation that you like to state as FACT.. Tohatsu is the only MFG to suggest plate be mounted below pad..that why the height difference in splash plate you like to harp about. All others state even or higher with newer motors..some of the older manuals state even or 1"below but that depends on hull type.

 

[Faztbullet]

And it just so happened that a customer dropped his rig off to have aerators changed. This hull is very similar to OP rig and has a 40EFI. It is set up from factory correctly.. one hole up,13 pitch Vengeance prop, AV plate even with pad. Asked customer how was performance and told will turn 5900 RPM and run 26MPH on speedo which is very close to Prop Calculators results...

 

[JimS123]

Tohatsu motors works with different height parameters compared to others brands in order to work spot on, achieve their max HP cowl stated along max prop thrust on any water cond from flat to windy choppy ones.

Will remaind you all that all Tohatsu motors have way taller lower leg plates compared to other brands. So cut the cast on stone crap that must be even with rear middle hull...

Been working on the lawn and garden these past few days so I've been preoccupied. Raining today, so I decided to go out in the boathouse with a tape measure and try to learn some things, if only for myself.

Interesting facts about AV plates, they sure have changed over the years. My Caveat is that my data was limited to my sample size, within the confines of motors built between 1919 and 2019.

Back in the early days, Ole Evinrude didn't get the memo and his motors had NO AV plate. As the years went by and motors got bigger HP, the plates got bigger.

In the 1950's they became prominent and by the 1970's they all looked similar.

I have only 2 Tohatsus. The AV plates are almost exactly the same size as recent manufacture Rudes and Mercs, and the vertical position is exactly the same.

 

[jimmbo]

Thru the 50s and 60s, OMC made their engines with longer than 15 and 20 inch shafts, Even when we had an Evinrude Boat, with the Engine mounted as speced by Evinrude(they did make both the Boat and Engine), the AV plate was about 1 1/4" inches lower than the Bottom of the Hull. I saw the same Boat with a Merc bolted on, and the AV plate was Flush with the Hull Bottom. Maybe OMC understood the Props they offered in those days were very poor regarding any occurance of Ventilation, so they buried them deeper. Our 14 ft Skagit was the same, though it was a 15" Transom

 

[JimS123]

The first outboard I owned with an adjustable bracket was in the early 1970's. It came with free installation so I let them do it. When I picked the boat up it was mounted all the way down and had no prop on it. The mechanic told me it had to be there, and he dissuaded me against putting on the SS prop that I had ordered with it. He wanted me to trade it for an aluminum prop. He said SS was too heavy and it would ruin the gears.

I guess we have learned a few things in the last 50 years. The old coot was a real nice guy, but I think he might have gone to school with Ole....LOL.

Anywhoot, a friend at the local ski club helped me mount and remount the engine. It was run in every hole and a performance curve done with each test. That was also my first use of a tach. Sure glad I didn't listen to the old mechanic.

 

[Sea Rider]

Sorry OP for repetitively highjacking you post but this online media repetitive offensive abuser needed moons back to be steeped down from his mighty boating pedestal. Continuing with the tech controversy...

Hey FB why did it took so long to respond, thought that the confrontation had ended already , well it’s not, having all the time of the world to respond due to the CoronaV government lockdown will refute both of your lasts posts. To start with, find extremely disgusting that you Deceive with Lies the on-line audience with your post for the sole purpose to make fun on me. Sooooo....

1-Pic 1 installation parameter does NOT correspond to a 2 stroke Tohatsu M40C motor, it’s a much larger HP model, this information is what fully corresponds. Doesn’t mention whatsoever the AV plate must be set even or "slight" under the middle boat’s hull as you erroneously and systematically love interpreting which applies better with motors having 1.5"-2.0" distance plates heights and this motor ain't so. It's a 4.0" one...



This pic corresponds to a Dry Installation, what you need to be fully aware of is at which lower leg plate's height is the hardened unobstructed flattened water flow passing by through the middle of both plates independently of the AV physical location with respect to the boat's bottom once the combo is taken out of water.

The second pic which was excerpted from a Yamaha Owner's Manual clearly states : that's not possible to provide complete instructions for every possible boat/motor combination. Proper mounting depends in part on experience, which have tons and the specific boat/motor combination. Which part of your brain doesn't understand this tech concept ?

You can deny a still pic as could be edited, but can't deny a video of the same outstanding water performance achieved with my "Usual Crap" installations. Video which have not taken the time nor interest to watch, That Merc 20 HP motor which is the rebadged version of the 20 HP Tohatsu has not been prop maximized just motor/transom height optimized. Now imagine running same with a spot on OEM prop maximization..

2-The third Etec pic information and your customer’s motor are BOLT ON ones which have nothing to do with a 40 HP Clamp Screw one and as usual your out of this world stupid comparison you like going for to withstand your posts. You’re the only one fooling yourself and fooling other followers as well, not me.

Hey JimS123, you finally realized that all motors brands does NOT have the same lower leg plates heights and this proven moron which still lives in the golden boating area has not realized so, that's why the constant knifing me.

Happy Boating

 

[JimS123]

Hey JimS123, you finally realized that all motors brands does NOT have the same lower leg plates heights and this proven moron which still lives in the golden boating area has not realized so, that's why the constant knifing me.

I'm sorry. You misread my post #45. What I said was that all motor brands DO have the same lower leg heights.

It's now quite clear that Tohatsu's mounting recommendations are different than the other manufacturers. Why? I dunno.

Nevertheless, I think this thread is resolved. Hope the OP learned what he needed to know.

 

[WesNewell]

If you want to lose up to 20% in speed and fuel economy mount your engine like SR's post. Not only that, if you don't have a splash well in front of the engine on your boat, expect water to fill up your boat when you plane out at wot. It's been proven thousands of times that the best performance is reached with the AV plate above the waterline at wot. That means the AV plate should never ever be above the bottom of the hull and most times above it by at least 1/2 inch.

 

[Faztbullet]

The distance of splash plate from AV has NOTHING to do with motor operation...it there to deflect water and running them deeper as Tohatsu suggests will deflect water upwards. It has to be higher to deflect more water than other brands . Oh and pic 1 is from pg.24 of Yamaha owners manual for a 40/50 HP(see attached). Maybe when you get to work on something that's not rubber, has a HP rating higher than 20 and not a Tohatsu you might see the error of your ways. You cannot deny that Factory owner manuals, service manuals, thousands of YouTube videos ,dealer postings and online posts go against the supposedly FACTS you spout for all motors.

 

[Sea Rider]

Hey guys throttle down, drop the anchor. So for both of you the posted video is pure BS, right ? That's the best lower leg height for such rebadged Tohatsu motor, works spot on at ALL WATER CONDITIONS, independently at which height is the AV plate finaly located when the boat is taken out of the water.

Hey NW, 20% speed reduction really ? have heard you say it many times before. Not even in dreams will that be possible, surely happens on the brand motors you like to boat with...

As the OP's post has been excessively contaminated with excessive information, will open a new post for tech discussion on the subject, will let you know the name of it, Will advance that won't be possible for both of you and any other boater that wants to join in the conversation to technically discredit what I satand for TOHATSU modern motors..That's all Folks...

Happy Boating