Johnson 115 SPL

[tmt]

I had a rebuilt power head put on last year warranty has expired. The compression is 100-90-90-85. The motor has never over heated. I have little blow by oil/fuel that comes out by the prop, I tilt the motor down and leave it there after running on water hose. My idle is at 1200 and in the water at idle the rpm go down to 750 or 800 (in gear). Should I pull the heads off or is there something I can do first.

 

[bktheking]

Re: Johnson 115 SPL

Try doing a decarb before anything.

 

[tmt]

Re: Johnson 115 SPL

decarb ?

 

[tmt]

Re: Johnson 115 SPL

Thanks I will do the decarb and then do another compression check.

 

[emdsapmgr]

Re: Johnson 115 SPL

You did not mention what cylinders had which numbers. Hard to tell which numbers go with which cylinders. The compression difference between heads becomes important on these OMC's. It is not unsual for the compression on one head to be different from the other head, by up to 7-8 lbs. So, if one head is 100/90 and the other is 90/85 you are probably ok. If the 100 and 85 readings are on the same head, that is a statistically significant difference.

 

[tmt]

Re: Johnson 115 SPL

OK did the decarb, and it worked great. I baught one 16oz can of seafoam and one can of seafoam spray, mixed the can of liquid with one gallon of gas and used the spray for the carbs and in the cylinders for 15 min. Idid this 3 times ran motor in between each spraying. Then ran the gallon of gas empty. Did another compression check and WOW one side has 110/110 the other 110/105. Thanks for the tip!

 

[bktheking]

Re: Johnson 115 SPL

Sounds like you had some carbon issues, do it every season as part of your maintenance, Seafoam is pretty awesome stuff!

 

[tohg2]

Re: Johnson 115 SPL

I'm a new member that has been watching the forum for a while. i've never had any questions that havent been answered already. i would like some insight on this topic though. i have virtually the same motor and conditions. the motor is a '96 112spl. the previous owner supposedly had the motor rebuilt years ago. when i got the boat i had the carbs rebuilt and the decarb done. in the end the compression ended up as follows:#1-100, #2-115, #3-90, #4-105. the tech figures the #3 cylinder was bored out and had oversized rings put in that have worn poorly. the motor runs well with a similar idle. 1200 in neutral and 900 in gear. i would just like some different opinions on the motor. would you trust it? or is it worth another rebuild? sorry to the original poster if i derailed the thread i just didnt feel it deserved its own topic.

 

[bktheking]

Re: Johnson 115 SPL

I would do the same procedure and remeasure your readings, carbon and 2-stroke outboards do not play nice together and cause readings to go out of wack as demontrated by the gent who started the thread, 90 is on the lower side to match the other 3.

 

[tohg2]

Re: Johnson 115 SPL

i had the decarb done twice when i got the boat. once when they rebuilt the carbs and again about a week later on my own. i have put about 20hrs on the motor since the decarb and compression test. i suppose it would make sense to do the test again now that i know the motor is running as strong as its going to get. as i said it runs well. although it seems a bit under powered. the boat is a 19' maycraft cc. at wot i see about 30mph. i'm more than happy with the speed but its pretty slow to plane. i tried 3 different props and settled with a 16x9 and transom wedges to help with the hole-shot. overall i am contempt with the motor's state of tune i just wonder how much different/better it would be rebuilt with correct compression. what kind of actual power loss would you expect from low compression on that one cylinder? 115 is and the bottom end of the recommended hp for the hull so i suppose repowering would make more sense than a rebuild.

 

[CaptainHook]

Re: Johnson 115 SPL

You settled on a 16X9 prop??????? Sounds weird to me...16" diameter will not fit on that lower unit. I had one with the V6 gearcase and a 15 1/2" diameter only gave a hair between the prop and cavitation plate. Infact the blades were larger than the skeg!! And 9 pitch????

 

[CaptainHook]

Re: Johnson 115 SPL

Oh yeah, I was running the 112 spl on a Wellcraft 19' center console and when I got it propped right with a 14 1/4 X 17 it gps'd 37-38 mph and that was with one cylinder down at about 65 psi.

I have since replaced the motor with a brand new Mercury 115 optimax and it is slower....about 35-36 mph

 

[emdsapmgr]

Re: Johnson 115 SPL

toh, your 90# cylinder is down 18% on compression, compared to the top cylinder. Certainly outside the "normally acceptable" range. Low compression will affect your performance. You can try another decarb on the engine-it certainly won't hurt it. You can pull the spark plug on that low cylinder and see if there appears to be any cylinder scuffing (aluminum transfer) from the piston to the cylinder walls. If there is none, you can keep running the engine the way it is till it finally requires an overhaul. This is a little off track, but double check to make sure the engine is mounted at the proper height on the transom. Engines which are mounted too low have excess drag and can have performance/fuel economy issues.

 

[Proselect]

Re: Johnson 115 SPL

I am a new owner of a 112 spl. Can some of you explain how to do the decarb procedure on this motor. This is something I would definately want to try and see if it makes a difference.

 

[ezeke]

Re: Johnson 115 SPL

Your motor has the schrader valve on the primer solenoid so you should use it with the aerosol product to do the de-carbon treatment. You can use it with SeaFoam's Deep Creep or with the OE product BRP Engine Tuner.

Instructions are on the BRP Engine Tuner can. You may need to do as many as three treatments if the carbon is heavy.

You will need the $2.00 injector hose, part #0763644: http://shop.evinrude.com/dyn_prod.php?p=763644

 

[bob johnson]

Re: Johnson 115 SPL

Your motor has the schrader valve on the primer solenoid so you should use it with the aerosol product to do the de-carbon treatment. You can use it with SeaFoam's Deep Creep or with the OE product BRP Engine Tuner.

Instructions are on the BRP Engine Tuner can. You may need to do as many as three treatments if the carbon is heavy.

You will need the $2.00 injector hose, part #0763644: http://shop.evinrude.com/dyn_prod.php?p=763644

does the mid - late 90's looper 115's have the same valve????

and why would someone do a decarb on a brand new rebuilt motor????

seems utterly senseless....

bob

 

[Proselect]

Re: Johnson 115 SPL

does the mid - late 90's looper 115's have the same valve????

and why would someone do a decarb on a brand new rebuilt motor????

seems utterly senseless....

bob

Not sure what a looper engine is, but my 112 is a 1994 and it has the shrader valve.

Yeah, not sure why you would ever have to decarbon a new engine, that doesn't make any sense.

 

[tohg2]

Re: Johnson 115 SPL

sorry i was way off with the prop. its a 13x19. when i replaced the plugs they looked well worn but overall clean. i looked in the clyinder through the plug holes as best i could and the cylinder walls look smooth. nothing out of the ordinary. i debated on pulling the head but decided against it. with how its running now i am just going to stick with it until something happens or i can afford to repower. i have often wondered about the engine height. the cav plate is even with the back of the hull. but when its up on a plane that plate is still plowing through the water. how does this look?

these pics were taken at wot running with 2 guys and about 5 gal of fuel. so pretty light actually. the boat normally holds 60gal. how is moving the motor up going to affect the boats sensitivity to trim changes? its not bad now. i put the wedges on to get better negative trim which helps with planing. the wedges also allow me to really push the nose down in a chop and plow through. i dont want to loose any of that ability with moving the motor up.

 

[bktheking]

Re: Johnson 115 SPL

Not sure why, because of this statement:

The previous owner supposedly had the motor rebuilt years ago.

Supposedly and knowing for a fact are 2 very different statements, last week and years ago are also 2 very different statements.


Do the decarb and repost your readings, unless I'm missing something here.

 

[bob johnson]

Re: Johnson 115 SPL

Not sure what a looper engine is, but my 112 is a 1994 and it has the shrader valve.

Yeah, not sure why you would ever have to decarbon a new engine, that doesn't make any sense.

the 115's came as loopers and crossflows...the loopers were 60 degree motors and the crossflows were 90 degree motors( block design)

little if anything interchanges between the motors even of the same year!!!

all the specials were 88 hp to 115 hp crossflows (I am pretty sure)

bob