50 hp Johnson

[mollywalk]

I wet sanded my lund Tri- Hull boat along with painting the Johnson outboard & the johnson trolling mtr.<br />I installed a new throttle spring when hooking it back up as I was thinking it may help to seat the throttle arm back to the idle position properly.<br />Before the motor would run high and hit hard when shifting into gear.Regardless of any correction to the linkage setting I could not fix it and I did have a company set everything before The project to my surprise the engine ran better but, the higher would still stick to high for shifting back and forth.<br />The carbs were rebuilt 4 years ago.<br />Anyway, the boat gets some very nice comment everytime I hit the lake and I manage to set the linkage after a few tries.<br />The reverse works fine and the idle is no problem.<br />I installed a new tach to check out my performace and it's running at 4800 to 4900 RPM's after planning level.<br />It will get to 5500 RPM's briefly just before planninglevel.<br />My question is, I have a 12.5 x 15 propeller in both steel and alum and was wondering ing if I need to have someone ajust it to 5500 to 5800 RPM's or do I consider a slightly larger prop.<br />I was thinking a 13.25 x 17 or so.<br /><br />Any idea's.<br /><br />Thanks!<br /><br />Bill

 

[roscoe]

Re: 50 hp Johnson

Something strange going on here. <br />The engine actually goes down in rpm AFTER it gets on plane?<br />That is backwards. Sounds like your prop is slipping a lot, and/or ventilating.<br /><br />Most motors will get the boat on plane in the 3000-4000rpm range, then increase rpm to "5500" after the boat is on plane.<br /><br />How long does it take the boat to get up on plane?<br /><br />"and was wondering ing if I need to have someone ajust it to 5500 to 5800 RPM's"<br /><br />Adjust what to 5500 to 5800 rpm?<br />You adjust the rpm higher, by changing the prop to a lower pitch. A lower pitch prop will get you up on plane faster, and let the engine rev higher at wide open throttle.

 

[mollywalk]

Re: 50 hp Johnson

Thanks for returning my question.<br /><br />I just place the use S.S. prop on so I am not sure if it has play in the brushing so I will try the alum I owned.<br /><br />One more thing is I had to increase the idl set screw yesterday to keep it running and that's when I got it to 4800 RPM's from 4200 RPMs.<br /><br />Planeing takes onle a few seconds so I have the power considering it's a 25 year old lund tri-hull deluxe.<br />I was wondering last night if I turn up the idle a bit more what will happen.<br /><br />A few years ago I had it measure at 5800 RPM's at full throttle so I know I need something but what?<br /><br />Perhaps i am not the linkage guru but was trying to ajust it mtself.<br /><br />Maybe I should make an appointment for a check.<br />The speed is great and run as fast as ever but it does sound a little differance.I can tell it not at top end by ther noise pitch.<br /><br />Any more information by you is much to be thank you for.<br />It hit 5500 RPM's just before planning so I guess after ajusting the idle and getting to 4800 RPM's is a clue.<br /><br />Your comments tell me I don't really understand how to set the linkage cables.<br />Thank you again!

 

[umblecumbuz]

Re: 50 hp Johnson

Bill,<br /><br />Is it the idle you're really adjusting? Because adjusting the idle shouldn't make that difference to the top end.<br /><br />Something doesn't add up somewhere.

 

[mollywalk]

Re: 50 hp Johnson

I only ajusted my idle again last week because it would quit on me even after the dock during the start and warm up period but crossing the first bay I notice the Tach was reading 4900 RPM's which was up from last week of 4200RPM's.<br /><br />Perhaps when I install the new thrttle spring and seen that it set the throttle arm much more forward I started to ajust the throttle cables.<br />One other thing I notice was the reverse throttle linkage do not really move much as before when it drops into reverse.<br />I guessing this is where I have the problem which may best be serve by a good mechcanic.<br /><br />The tach is new but who to say my sending unit on the motor is up to pair.The tach was install after the wet sanding and painting the motor so I really don't have a history of knowing the RPM's buy once several years ago.The motor is 25 years old.I do get top speed so next time out I am going to turn the throttle a bit more to see if for some reason it jumps the RPM's up.I will take another look at setting the forward and reverse cables.<br /><br />I through when I unhook and painted the motor it was no big deal but since it was where it was I felt a good place and time to install the throttle new spring was right.<br />I look at the spring and it appears only one way to install it.<br /><br />After I did the throttle arm was way forward so I guessing the old spring loss alot of it's tension.<br /><br />Anyways the throttle does go all the way back to seat the idle screw to the stop. So if I am about 800 RPM's off perhaps I will get it or take it to some old motor pro's I took the motor to beofe.<br />They charge $75 per hour which isn't bad but I been out of work for a long time.<br />It just drives my wife crazy to see me spending money on the old boat but everytime I get to the lake someone ask me (How old is that boat and man it looks great!).Otherwise I would do just that.<br /><br />The botton line is what I see is the reverse cable and linkage should move to ingage the reverse so there's where I am thinking of ajusting again. Otherwise the two old motor pro's will be able to do right.<br />Thank for any input.<br /><br />I do know the idle setpoint has nothing to do with the topping out of the motor but what else can I say for the increase RPM's over last week.<br /><br />I can also tell you when I use reverse last year if I max the control arm all the way back the motor would as you can guess kick out of the water but now a nice steady reverse speed which is a good clue. It's is great for trolling but I always just use my 25 year old newly painted (same color as the outboard - 1959 warm white) johnson 28# thrust trolling motor.<br /><br /><br />So what I am saying if I were to ajust the reverse to a more agressive speed than that may help and I bet I could see the reverse arm moving and ingaging reverse bit harder engagement like before where you felt it going intro gear.Somewhere from last year to this year settings would be great for the reverse so not having the motor kicking up out of the water again when in reverse. <br /><br />I did do one more thing now that I thinging about what my wife would say and that is I did turn out the throttle arm on the forward gear which advances the cards a bit more.<br />I wanter the carbs to be all the way open when at full throttle but a turn or two may not be anyting but you guys tell me. It just seem that there was a little more left of the carb linkage to be move .Perhaps I could turn the connecting rod back again to see if that makes a difference.<br />Perhaps it will.<br />You tell me.<br />Thanks!!<br /><br />Have a great weekend!