Motor to low?

[jonboy2542]

Hi,

I have been having some issues when cruising in the pontoon. I can ride for a while and not change anything and all of a sudden rpms would jump up and I lose speed. I can back of the throttle and go back into it and everything is fine and then it happens again. I have been thinking the motor is to low but I am unsure. It's a 22 ft pontoon with a 50 Mercury.

 

[ahicks]

Motor is not too low. If anything it's too high. That's generally one of the reasons you'll see that big increase in rpm's until backing off the throttle. The prop is sucking air from the surface, rather than water in front of the prop.

Another one you see, especially on older props, is where the prop is slipping on the rubber bushing between the prop and the hub. Those are easily checked with a magic marker. You make a mark on the hub, another on the prop, and go for a ride. After you get one of the rpm increase spells, you check to see if your marks are still lined up. If so, that's not your issue.

What's going on when the rpm's jump? Are you riding on a swell? Waves? Anyone/anything moving on the boat?

 

[jonboy2542]

When the RPMs go up, it usually happens at random. It's happened with 3 people on board and with 10 on board. Never has happened when I got another boats wake. I have looked at the motor while running and I don't even see the cavitation plate. The motor is at its lowest setting and is usually trimmed down

 

[HotTommy]

The usual test for the hub is to put waterproof witness marks on the hub and propeller. After the next time you experience the symptom, check to see if the marks are still aligned. If not, the hub is failing.

 

[Sea Rider]

If the prop is found in excellent wotking order, trim motor to 90 deg and leave it there, with deck load evenly distributed go for a wot run on flat calm water cond and have someone pull their head side of motor and check at which lower leg height did the water flow passed by after exiting the middle tube. Is the exiting water flow completely flat undisturbed or disturbed one ? Check the possible 4 lower leg's water performance heights and report which one was found on your test...

Open and read or download a PDF file information regarding motors installations : : https://jmp.sh/k4ByUsP

Will have a clue on what's going wrong with your current motor/application install, lots of pics, drawings, illustrations and their tech explanation to better the propulsion on anything that floats powered with an outboard motor..

Happy Boating

 

[Faztbullet]

Open and read or download a PDF file information regarding motors installations : : https://jmp.sh/k4ByUsP

Read this advise and remember it mostly opinion of a single person and has a lot of misunderstandings.....

 

[Sea Rider]

Read this advise and remember it mostly opinion of a single person and has a lot of misunderstandings..... [/QUOTE

I understand that your opinion comes from a oldie boater mentally aging real bad that doesn't want to understand that the motors have evolved through the years but want's to stay boating and giving opinions that olny applies well to those Jurassic narrow plates gap found only on medium and high HP motors you like to boat and surely will die boating with.

It was a matter of time for you to show up and descredit my post as usual which love doing, seems you don't have anything better to do or contribute with something positive.. Yep wise guy king of the I know all. Let the OP try what's suggested he has nothing to lose and much to gain if understood well what posted, SO BUG OFF.

Happy Boating

 

[Faztbullet]

You have been harping this BS since 2014... The spacing between the splash plates makes no difference on engine performance !!!! Your "facts" do not apply to other engine brands, just mainly Tohatsu as they have a water inlet under AV plate to assist in cooling ,thus needed to mount lower than others.. You state mounting height is not in engine manuals is strictly hogwash as every motor makers manual shows normal everyday mounting/usage height...Your small hp/small boat "opinions " do not apply to all boats....go pound sand.

 

[ahicks]

SeaRider, I would ask that you keep in mind the fact we are talking about a pontoon boat. They're really not something that's designed to plane out well leaving a clean wake in back of the engine pod - not in my 45 plus years experience with them anyway. They will on occasion, despite all the issues, actually get up and plane, though not well. There will often be water splashing EVERYWHERE in the vicinity of the motor, from all sorts of sources. Point being, the pictures you've supplied are of very little value, possibly even misleading to a newbie.

With all of the variables in play with a 'toon, it's easiest to start out with the engine quite a bit lower than what a full on planning hull will run. This helps take into account the potentially dirty water flow fed into the motor, changing loads, differences in tube diameters and that effect on motor height, as well as the effect boat wakes and wave action have on a hull like this.

It's only at that point where if there's an emphasis on speed (owners discretion) where you can try raising the motor to see what happens.

 

[GA_Boater]

Gentlemen - Please express your disagreements in a civil manner. There are good opinions on both sides and please remember there are so many variables that one-size solutions do not exist.

I'm old so my mental processes are suspect and have pounded sand more than once, so I take offense with some of these comments. Be kind to me and others. Especially others!

 

[Sea Rider]

Hey Ahicks, know how toons work perfectly well, don't have to school me. My boating club has 3 of them, all 3 has been transom lowered (height modified) due to extreme prop aeration, now all 3 motors performs top at all water cond at fast displacement speed or even at plane with 0 water splashes out or side of motor.

Question to the OP, why is the 50 HP motor sitting at its lowest setting and trimmed down ? All motors should run trimed to 90º deg when running at fast displacement or plane speeds which all OB manufacturers recommends on each of their respective Owner's Manuals, if skeptic check anyone's HP. With respect to which is the best motor height, is the one which gives the best prop thrust, serve yourself..

For the usual top notches boaters how about his boat/motor combo installation, would you say that's a correct neat install and complements well with the motor/transom installs you swear by and love going for....

Happy Boating

 

[Faztbullet]

OMG that motor in pic AV's plate is above the surface!!!! Right where it should be!!:thumb::thumb:

 

[ahicks]

Hey Ahicks, know how toons work perfectly well, don't have to school me. My boating club has 3 of them, all 3 has been transom lowered (height modified) due to extreme prop aeration, now all 3 motors performs top at all water cond at fast displacement speed or even at plane with 0 water splashes out or side of motor.

Question to the OP, why is the 50 HP motor sitting at its lowest setting and trimmed down ? All motors should run trimed to 90º deg when running at fast displacement or plane speeds which all OB manufacturers recommends on each of their respective Owner's Manuals, if skeptic check anyone's HP. With respect to which is the best motor height, is the one which gives the best prop thrust, serve yourself..

For the usual top notches boaters how about his boat/motor combo installation, would you say that's a correct neat install and complements well with the motor/transom installs you swear by and love going for....

Happy Boating

If you "know how 'toons work perfectly" like you say you do, please explain why you aren't using pictures or diagrams of them when trying to make a point? Using pictures (or diagrams) of a planning hull at speed are COMPLETELY irrelevant and could easily be confusing to somebody trying to develop an understanding of what's supposed to be going on......

Like your latest pic for instance. Please explain, in layman's terms (I'm stupid so you'll need to speak clearly and slowly), how ANYTHING in that picture has ANY relevance to a pontoon boat? -Al

 

[Faztbullet]

Not all toons are alike..different tube designs also and have different speed toons..some below 30MPH some below 50 MPH and some above 70MPH.

 

[Sea Rider]

If you "know how 'toons work perfectly" like you say you do, please explain why you aren't using pictures or diagrams of them when trying to make a point? How ANYTHING in that picture has ANY relevance to a pontoon boat? -

Oh C'mon Ahicks, toons are not what like boating with. Next time will shot some pics of the toons just to please yourself and explain what have been done to them. Is just a matter to sit the motor on transom at a certain height for the toon to experience the best water performance according to each one's particular taste. As a matter of fact Fazt swears by the 1 setting, I swear for the 3er setting, which setting is your particular taste 1-2-3 ?

Happy Boating

 

[ahicks]

Sea Rider, don't do anything on my account. I just don't care what you've done. The guys that need help are the ones that might like to see something relevant regarding some of your explanations.....

Once again, you show a nice installation on a conventional hull - but the rest of us are talking about pontoon boats! Not the same!

 

[Faztbullet]

As a matter of fact Fazt swears by the 1 setting, I swear for the 3er setting,

Uhh you got that backwards......#3 for performance/stepped hull...#2 for toon..you prefer #1.

 

[DeepCMark58A]

I think that the companies that make pontoon boats, you know the ones with design engineers on staff know exactly how high or low a transom needs to be to work with standard short or long shaft motors.

 

[ahicks]

I think that the companies that make pontoon boats, you know the ones with design engineers on staff know exactly how high or low a transom needs to be to work with standard short or long shaft motors.

Myself, I believe there may be a "design engineer" on staff at some manf's, but I would never make that assumption about all of them. Not with some of the dumb mistakes I've seen. I would LOVE to have a talk with some of the "design engineers" regarding permanent gas tank installs for instance - the inaccessible fillers? I could go on, but after nearly an entire lifetime spent around 'toons, there's no way I would think anyone with a hard earned engineering degree would would put his name on a lot of this stuff.

My thought is there are commonly known "best practices" based on the experience of senior staffers that are used to build these boats, and there's a good reason motors come with more than one set of mounting holes. -Al

 

[JimS123]

And yet another thread where the Original Poster doesn't know what to do because of all the contradictory opinions.