1997 M40C Stalling

[MarvinGabriel]

Yep. I’m replacing all of the nylon and plastic. Some of them just cracked apart when I removed them.

 

[MarvinGabriel]

Thanks. I'm STILL waiting for parts, and the CRC. The engine still isn't right. It runs out fine, and gets my 1648 Lowe Big Jon up to maybe 23mph with me and my daughters in the boat. That's fine for my purposes...but it still idles rough, and doesn't "feel" right. I'll be changing all of the nylon parts when they get here, and do the CRC treatment you suggested, then report back. I wonder if these Champion spark plugs are to blame? They are brand new, but I've had issues with Champion before.

 

[Sea Rider]

I wonder if these Champion spark plugs are to blame? They are brand new, but I've had issues with Champion before.

Not a big fan of Champion Spark Plugs as have boxes of the NGK ones. The factory delivered spark plugs are : NGK B7HS-10 or BR7HS-10. Champions are : L 82C or RL82C all must be gaped tight to 1.0 mm with a metal feeler gauge.

CRC should make the motor to run much smoother throughout all the throttle range specially if the motor has never been decarbonized before in its entire boating life.

Happy Boating

 

[MarvinGabriel]

OK, I'll just wait patiently for it to show up. And I'll change those spark plugs. I knew I shouldn't have bought Champions anyway. I gapped them the same as the NGK spec. The store sold me Champion L77JC4 plugs. They're supposed to be the same heat range as the L82C but who knows?

 

[Sea Rider]

OK, I'll just wait patiently for it to show up. And I'll change those spark plugs. I knew I shouldn't have bought Champions anyway. I gapped them the same as the NGK spec. The store sold me Champion L77JC4 plugs. They're supposed to be the same heat range as the L82C but who knows?

A Champion L82 plug is hotter than a L77 one which is colder, buy a set of Champion L82C or NGK- B7HS-10, both are non resistor type spark plugs. A colder plug will foul much faster than a hotter one at low rpm range. Install the heat range the manufacturer recommends it's best for his motor, crazy store employees will sell you what they think works best...

Happy Boating

 

[Sea Rider]

Moons back made a Tohatsu M40C re install powering a Boston Whaler 15 footer, had to rise the transom's height quite a bit due to lower leg's excessive water splashes. Those M40C having tall plates gap (3) likes to be seated at 90º at an optimum transom height for the incoming flat water flow to skim at plane right under the upper plate's protruding guide as possible.

Once there will achieve the best prop thrust match and outstanding water performance on all water conditions and at close tight turns. If need to modify the transom's height by raising or lowering it to dial "that spot setting" it's your homework. At any other lower leg height, check which water performance to expect (2) at plane.

Once there can go for a prop maximization for boat to literally jump on plane at wot. Will be best to install an induction tach and a tiller extender for easy long distance steering.(6)

Happy Boating

 

[MarvinGabriel]

Well, I've already got an aluminum plate to get the engine higher, since it's a long shaft, and it's on a 1648 Jon Boat with a 16" transom. I'll take some pictures of the installation, and post.

 

[MarvinGabriel]

Well, I've already got an aluminum plate to get the engine higher, since it's a long shaft, and it's on a 1648 Jon Boat with a 16" transom. I'll take some pictures of the installation, and post.

As I suspected, this has already been done. The water would be just under the top cavitation plate.

 

[Sea Rider]

As I suspected, this has already been done. The water would be just under the top cavitation plate.

A terra firme installation nor the nicest picture means a thing what counts is when at wot at which lower leg height does the water flow crosses by with motor set at 90 deg and deck load evenly distributed to work top on all water conditions which is key. If with time click and read this outboard motor installation review at :

https://jmp.sh/k4ByUsP

Has nice information, pics, tech illustrations that speak for themselves....

Happy Boating

 

[MarvinGabriel]

Ahhhhhh. Gotcha. I'll have to look when I hit the lake next time. Still waiting on my CRC. I should have just bought it locally. Saved $8.00 but still waiting. The boat planes out well, and never porpoises or anything, but probably isn't really optimal. I need a new prop due to contact with rocks, etc. I suppose I should put on my inductive tach and see what it's really doing. I feel like it's running great at WOT, but still has plenty of power to go. But still, it's a Jon boat. It's basically a heavy, square object pushing into the wind, and with my daughters and I, and out gear, that's probably an additional 500 lbs, on top of whatever that old tug weighs! LOL 2 batteries, 12 gallons of fuel, maybe 50 lbs of added storage and decking...I don't really expect much more than the 23-24MPH that I get now. Usually, I'm trying to go slower, which is why the idle being messed up is my main complaint. Getting somewhere quickly just isn't an issue. I fish Lake of the Ozarks and Truman Resevoir. They are LONG, Snake-like lakes, with plenty of boat ramps! I just drive to the area I'll be fishing that day.

 

[MarvinGabriel]

Like this?

 

[Sea Rider]

Ideal would be to install the induction tach, load the boat as will be used, distribute deck load evenly which is key. On flat calm water condition go for a wot run and report the max wot rpm achieved. That motor revs 5200-5800 factory stated. Ideal would be to rev at max throttle to at least 5500 rpm although max rpm range is preffered. Just need to prop the motor right.

The posted pic is not that clear. Will that boat be taken out of water any time soon ? if so post a clear pic of the loewer leg shot sideways showing both plates to have a look. Once correctly proped can run the motor to the rpm range you feel most comfy with...

Happy Boating

 

[MarvinGabriel]

Ok. The boat stays trailered, so this is easy.

 

[MarvinGabriel]

[No message]

 

[Sea Rider]

Have you read fully the posted link, ? there's all the info you need to know and plainly understand...

OK, last try :

-Trim motor to 90º-
-Being a tiller motor sit a mate up front to balance evenly the deck load for boat to run parallel to the water level.
-Go for a wot run on flat calm water cond. Full throttle is better than just plane at reduced throttle.
-VISUALLY check at which lower leg is the water flow crossing in between plates ?
-Report your findings

On these tall plates gap motors the ideal match is flow passing right under the upper plate guide as seen in pic. If need to modify the alum mount height for that to happen it's a different story. Under no circumstances should the trim be moved away from 90º, that's where the prop if with a tall water bed level achieves the "best prop thrust".

The water flow could pass right through any of both plates, if towards the AV plate will only be good for straight water courses on near flat calm water cond along excessive prop aeration. The upper plate gives the best water performance under all water conditions and close tight turns at speed.

Note : Would you say that there's a undisturbed flat water flow passing right at middle of the boat's rear bottom, asking this as the transducer could be achieving some form of water splash at speed around that area and the middle leg receiving it "disturbed" when should be flat even.

Happy Boating

 

[MarvinGabriel]

The water passes right under the top plate, as you describe. Maybe 1" under it, maybe less. The motor is trimmed at 90 degrees, relative to the bottom of the boat. The transom is not 90 degrees, relative to the bottom of the boat. I read all of your info, and have confirmed that this setup is very close to what you are saying. The water is undisturbed going into the prop, and the outflow is flat, and there's not a lot of excessive splashing, beyond that which the bottom of the stern generates.

 

[MarvinGabriel]

OHHHHH. I see now. I meant the TOP plate. That little one above the one you mention. I'm way too deep for that, when on plane. I guess it's time for another boat! There's no way I could raise the motor that high without putting too much leverage against that transom. I understand completely now.

 

[Sea Rider]

Check post 46, second pic, at which lower leg plates is the flow passing by at plane ? Bottom pic is with flow passing "under" the upper plate....

Happy Boating

 

[MarvinGabriel]

It's passing WAY over the plate labeled 1. Way up in the splash area, just under that tiny plate at the top...not pictured in your pic.

 

[MarvinGabriel]

[No message]