Outboard mounting height 1985 Johnson 115 v4

[emdsapmgr]

Re: Outboard mounting height 1985 Johnson 115 v4

The 85 115 was a bubble back type engine, indicating it is a higher performance model which has better exhaust breathing and larger carbs. It should be propped to run all day at 5500 WOT-the top end of the normal factory rpm rating. Once it is propped to run WOT at that rpm, you will maximize your performance/economy at all rpm's. You'll notice a huge difference when you get the jackplate mounted.

 

[scottcab]

Re: Outboard mounting height 1985 Johnson 115 v4

Thank you everyone for the advice. I have just been fortunate enough to receive the Hi-Jacker manual jacking plate from a couple family members for my b-day (pays to have a wife that pays attention). This jack plate has 6" of setback. Only downside being I think I am going to have to change my Steering cable out for a longer one on account of it being kinda tight as is.
Either way, I know I will need to fine tune this by running it and watching where the water line is hitting, but as a ball park for set up, where do I want the anti-cav plate? Is 1" above the keel a good starting point or should I put it even? This plate will give me 4" of vertical adjustment from there, so even at even I can get it to 4" above keel. I will update after install and a test run with new numbers.
Thanks again for all of the help,
Scott

 

[Haffiman]

Re: Outboard mounting height 1985 Johnson 115 v4

The danger of lifting to high on that engine is that the upper holes of the water intake might suck air and reduce cooling. I would have started at 1,5-2" above if you have a clean V-bottom at around 17 degree. If a 'pad', max 1" up.

 

[bob johnson]

Re: Outboard mounting height 1985 Johnson 115 v4

since the jack is adjustable.....I would set the jack to its lowest setting, then mount the jack on the transom holes- and motor mount hole combination that has the cav plate even with the bottom of the boat's keel.....

you should never really NEED to go lower than that...and you can adjust Upwards for performance until you cavite at top end...( if you can go that high) and then back down an inch from there....so when you hit rough water you still have decent performance.

it would be a waster of the jack plate to set it up so you ahve travel BELOW the keel!!!!!!!!!!!!!!!!!!!!!!!!

with that set back, you might be able to achieve top end and have the cav plate 2-3" above the keel!


if you can reach that high...but i think with the bolt hole combos of mounting PLUS the jack plates travel...you should fall into the perfect sweet spot you need

bob

 

[SparkieBoat]

Re: Outboard mounting height 1985 Johnson 115 v4

start out 2" above keel. get it running wide open then trim it up some, you should feel it hit the sweet spot with out too much trimming. after the sweet spot you should start to blow out (increase RPMs with no increase of speed). use a gps to watch speed. report back top speed and RPM without any blow out. test it in a few turns. I set mine so I have to trim down a little for sharp turns, it may blow out some in a hard turn. if it is a bbad problem you may need to lower 1". if it does not blow out at all, go up another inch. I like my props as high as I can getem. double check your pee stream to make sure your water pump is picking up good at all RPMs

 

[bob johnson]

Re: Outboard mounting height 1985 Johnson 115 v4

get a temperature sender for both heads...and KNOW the temps in real time instead of waiting for an alarm you hope works.... that way you can shut the motor down BEFORE damage occurs..

as for super fine tuning and pushing that motor up for the last 1 mph but worrying about blowing out in the turns...

Id personally say....dont push it that far....heck you got the worng motor in the first place! once you get that motor running in the right rpms...just be satisfied!!! if you set it up to not blow out in the turns...you are golden , you really DONT NEED the extra 1-2 mph raising it might give you....

you would have made a monster step up from where you were before you added the jack plate

remember no need to go below the hull... when the jack is all the way down!!!!

bolt it on so its all UP from the keel...that way its only installed ONCE!!

too bad they didnt buy you the 4" set back version.....on that short a boat with that big of a motor......you probably dont want a LOT of setback..


bob

 

[scottcab]

Re: Outboard mounting height 1985 Johnson 115 v4

Okay all. All jacked up and ready with new numbers. I installed the Hi-Jacker manual adjustable as discussed. Mounted the motor in the bottom holes, then jacked it all the way. I am utilizing all 4" of vertical lift plus the bottom bolt holes. The anti-cav plate is about 1" above the keel and I am maxed out on lift now. The results: The boat ran very well, it felt good and planned off nice and fast. The motor also handled well. Unfortunately, my speed and RPMs saw very little change. My new optimum trim angle is about 5 seconds of trimming from being all the way trimmed in. My new max rpms was 4550rpm at 36mph. This is only 300rpm and 1.5mph faster. I did like the feel of the boat more jacked up, but I am wondering why my speed is falling short. Is this going to be the fastest I can get her to go. I know that I probably need to change propellers. I am currently running the 17 pitch aluminum prop (it ran about 1mph faster than the stainless 17 pitch) no clue why. I know that I want to be at the top of the WoT range with my lightest load (which would be 5500rpm). Do yall think that going to a 15 pitch will bring me up 800-1000rpm? Also, what do yall anticipate my top speed to do if I drop from 17 to 15 pitch?
Thanks
Scott

 

[wilde1j]

Re: Outboard mounting height 1985 Johnson 115 v4

You're only going to gain 300 to 400 rpm. Still way to low. That motor should be turning 5500 or more @ WOT. Are you sure tach is reading right? Has gearcase ever been changed?

 

[Haffiman]

Re: Outboard mounting height 1985 Johnson 115 v4

I believe you may be not too far off. However a clip taken from another boat as well as some pics showing the bottom and installation of your boat on the trailer might be useful.

 

[scottcab]

Re: Outboard mounting height 1985 Johnson 115 v4

You're only going to gain 300 to 400 rpm. Still way to low. That motor should be turning 5500 or more @ WOT. Are you sure tach is reading right? Has gearcase ever been changed?

Hi Jim,
Yes the gearcase has been changed long before I bought it. It is a 1985 1.6L OMC seadrive powerhead on what I am guessing is a similar year midsection and lower unit from a Johnson or Evinrude. Maybe the mid and lower that it is on will not produce the same numbers that the manufacture rates for the oms seadrive??

I believe the tach is correct. It is set to the 5 position on the faria gauge. It seems correct at idle, but I don't know how to know for sure. It sounds right to me when running, but I am a novice.

Please let me know.
Scott

 

[SparkieBoat]

Re: Outboard mounting height 1985 Johnson 115 v4

tach should be set to 6P. once you get an accurate RPM reading, you will probably end up with a 15 pitch prop.

 

[wired247]

Re: Outboard mounting height 1985 Johnson 115 v4

I'm running essentially the same powerhead in a 16 1/2' boat with my anti cav plate an inch above the keel and with a 15, 17 and 21 pitch props I'm running into the rev limiter at 5800-6000 RPM. I'd expect a lot more rpm's out of your engine

 

[scottcab]

Re: Outboard mounting height 1985 Johnson 115 v4

tach should be set to 6P. once you get an accurate RPM reading, you will probably end up with a 15 pitch prop.

Sparkie, Thanks for the reply. When you say I should be set to 6P, does that mean 6 pole or to the 6 setting on the tach. The tach is a faria outboard tach. When I read the manual for the tach, I understood it to tell me that I needed to use the 12pole setting which then coordinated to the 5th setting on the tach. The tach has numbers 1-6 on the adjustment screw. The chart only reads 1-5. What am I misunderstanding here?? I will include the screen shot of the manual for the gauge. Please someone that understands these things shed some clarity on my situation.


Thanks in advance,
Scott

 

[SparkieBoat]

Re: Outboard mounting height 1985 Johnson 115 v4

I am not sure why it says 12 P, but if that is what the tach manufacturer says, then I guess you got it right. most tachs have only the pole numbers, and OMC motors are set to 6 Pole. the instructions say " a system check tach or a 2" gauge are required" I am not sure what that means. maybe you could borrow another tach to double check that one. you need to know for sure your tach readings in order to properly prop the motor.

 

[scottcab]

Re: Outboard mounting height 1985 Johnson 115 v4

Faria OB Tachometer on 1985 OMC Seadrive 1.6l (johnson 115): I contacted Faria (the manufacture of the tach) today. The customer service rep informed me that the motor has a 12 pole alternator which would send 6 pulses. He stated that for the Faria tach the 12 pole position should be used which is the number 5 on the calibration dial on the back.

Test Run results for informational purposes: Before Jack plate, 4200max rpm at 33.7mph After Jack plate, 4800max rpm at 37.4mph
Also, improvements in handling and a slight improvement in planning time (see videos). Also, the jack plate remove the extra strain on the motor and the "water show" that was present before.


Do yall think that the 15 pitch prop is the right call from here? If so is the stainless prop worth spending money on or should i stick with a aluminum.

Thanks
Scott

 

[sutor623]

Re: Outboard mounting height 1985 Johnson 115 v4

Scott, did you say you guys just had a baby? If that were me I wouldnt be tossing $3-400 into a SS prop, but thats just my opinion. Sounds like if you want to be at 5500RPMs with a light load, maybe a 13P prop, or a 15 with a smaller diameter.

 

[bob johnson]

Re: Outboard mounting height 1985 Johnson 115 v4

youll gain more if you go with a SS 15 p prop over the aluminum 15 pitch. maybe 300 rpms.( total over the 17 you have now)
id look closely at your boat...wondering if it is overloaded....maybe the foam is saturated..

with that small a boat.....it seems you should be spinning way faster.....with a 17P.

how much does that boat weigh? more than 2500 lbs? 3000lbs?

or your motor isnt running up to full potential


most places that sell props will let you try them before you buy.

good luck

bob

 

[sutor623]

Re: Outboard mounting height 1985 Johnson 115 v4

most places that sell props will let you try them before you buy.


bob

Is that so? Hmmm never tried but sounds like a great idea.....

 

[Haffiman]

Re: Outboard mounting height 1985 Johnson 115 v4

SST on a 15" pitch is a waste of money, Alu will normally function just as well in that speed range. From 19" and up in pitch I would recommend SST. Would however still like to see some pics of the rig and bottom, you should normally be able to pull a 17" at around 5K on that size of boat.

 

[scottcab]

Motor issues? timing or carb link? plus photos

Motor issues? timing or carb link? plus photos

Haffiman, here are the photos you requested.

I will try to figure out what the problem is. I think the motor might not be running perfect or something. When I first get out on the water and run, it runs great. After about 20-30min of running hard, the motor starts to act like it misses. instead of running smooth like when first started, it runs even, then sounds like it misses once or twice then revs up a touch to act like it is trying to compensate, then back to even. Then it repeats that cycle. The missing is less at idle and worse between idle and mid range then a little better at full throttle. The carbs have just been pulled off and cleaned. As I was cleaning the carbs, they seemed really clean to start with. Consequently, I didn't pull the welsch plugs (already regretting that for lack of piece of mind). I am also thinking that my timing might be a little off. Unfortunately, I don't own a timing light and wouldn't know what to do even if I purchased or borrowed one. I do have the OMC service manual, but the steps seems alittle out of my range.
The last thing I noticed that might be affecting my WoT rpm is that I don't believe that the butterfly in the carbs are opening all the way. I attempted to follow the service manual for linking the carbs and settings. First, I set the butterflies at just closed when you move the control just into forward gear. Then, after moving the control to WoT, I believe my butterflies should both be at just parallel. They seem just shy of parallel angling just slightly down and forward.

Last questions, I notice a dark almost black color fluid draining from around the prop. It seems like the consistency of a light oil but doesn't smell of oil. It almost smells real lightly like fuel. Not sure if this is a problem or not.

Thanks All,
Scott