# Johnson 25hp question



## DaveP (Aug 25, 2018)

Folks, I just picked up a new to me Lowe 170 with a Johnson 25 on the back (Model #J25ELSSS). This boat has been modified with three batteries in the back and currently has about 3/4 tank of gas. I've put new plugs in it, added Stabil to the tank since it was sitting for a few weeks before we got it. The motor is tucked back to the transom in the closest hole (manual tilt) to help keep the nose down. 

With two humans on board it'll spool up just fine and start to plane but it sounds like it's not reaching full RPM. Now, this is by ear only since the rpm gauge is inop. It shows @15 MPH pretty consistently on the dash, occasionally creeping up to maybe 16-17. If this is what it is, I'm fine with it. But it seems like it wants to rev more but just never gets there. Prop is stock.

Thoughts?

Thanks in advance!


----------



## Weldorthemagnificent (Aug 25, 2018)

Is it planing ?


Sent from my iPhone using Tapatalk


----------



## DaveP (Aug 25, 2018)

I would say so, but it doesn't seem fully on plane if that makes sense. Still runs slightly nose high, but not bad.


----------



## DaleH (Aug 25, 2018)

Right plugs? Plugs gapped to 0.030”? 

With the motor off, and cowling off, twist the throttle all the way open- does the throttle linkage allow it to go FULL up against its stop? Also take off the air silencer, with throttle all the way open, do the throttle plates open all the way up? They should be ‘sideways’ with their edge towards you.

If your speed is being read by an ‘in water’ pitot tube, those are notoriously inaccurate and that speed sounds low for that hole in motor to me.

It’s just me, but I find it hard to do any diagnosing or reasonably accurate ‘predictions’ on a motor’s status without having a good tachometer on board and operating. Proper RPMs and performance are all about having the right prop on the motor for you rig, gear and load you carry.

Check out the propeller calculator that is the sticky under the Motors forum.


----------



## Weldorthemagnificent (Aug 25, 2018)

With the three batteries in the back, I have to wonder about weight distribution. 


Sent from my iPhone using Tapatalk


----------



## GYPSY400 (Aug 25, 2018)

3 batterys plus gas and driver.. there is too much weight in the back end.. 
Get rid of the batterys

Sent from my SM-G903W using Tapatalk


----------



## nccatfisher (Aug 25, 2018)

GYPSY400 said:


> 3 batterys plus gas and driver.. there is too much weight in the back end..
> Get rid of the batterys
> 
> Sent from my SM-G903W using Tapatalk


I have three in mine, plus 10 gallons of fuel but it is all up in the front with a 25. Makes a big difference with the weight distributed evenly.


----------



## ktoelke54 (Aug 26, 2018)

My first step would be to shift weight from the rear to the front of the boat. I believe that motor with the stock prop should run at least in the low to mid 20’s to be in its power-band. Getting the weight balanced in the boat will get you more speed, but if it doesn’t get you where you want to be, dropping one pitch, two at the most, on these small motors makes a big difference. But I’d check the rpm’s with a tach first. 


Sent from my iPhone using Tapatalk


----------



## DaveP (Aug 26, 2018)

DaleH said:


> Right plugs? Plugs gapped to 0.030”?
> 
> With the motor off, and cowling off, twist the throttle all the way open- does the throttle linkage allow it to go FULL up against its stop? Also take off the air silencer, with throttle all the way open, do the throttle plates open all the way up? They should be ‘sideways’ with their edge towards you.
> 
> ...



Correct plugs, NGK called for 040, will regap to 030 and retest. Throttle opens to stop (console boat, so side throttle). Speedo is the plastic finger type that falls off the bottom of the transom. I will take a look at the tach to see if it's unhooked or what.


----------



## DaveP (Aug 26, 2018)

ktoelke54 said:


> My first step would be to shift weight from the rear to the front of the boat. I believe that motor with the stock prop should run at least in the low to mid 20’s to be in its power-band. Getting the weight balanced in the boat will get you more speed, but if it doesn’t get you where you want to be, dropping one pitch, two at the most, on these small motors makes a big difference. But I’d check the rpm’s with a tach first.
> 
> 
> Sent from my iPhone using Tapatalk



I would like to but that's going to take a lot of rewiring since it's set up with an on board charger back in the bilge for all three batteries. I'm going to try running some seafoam through it as well. Can't hurt.


----------



## Pappy (Aug 26, 2018)

If your running quality is good at idle then your engine is well sealed and you will be wasting money on Seafoam. 
The suggestions on re-distribution of weight are the correct suggestions. With a small boat and limited horsepower it is all about planing surface (area) Your boat is loaded similar to full sized bass boats minus the horsepower. By moving the weight forward you will increase planing surface and your issue will be minimized. 
All you have to do is move the batteries on a temporary basis to verify. After that you can make a permanent choice.


----------



## GYPSY400 (Aug 26, 2018)

Why 3 batteries anyhow? I run 2 size 24, one in the back for the electric start and all the boat accessories, and 1 in the front for the bow mount TM.

Sent from my SM-G903W using Tapatalk


----------



## MrGiggles (Aug 26, 2018)

I'm guessing 170 means 17ft? If so, that's a lot of boat for a 25.

As mentioned, move two batteries up front. You likely have too much weight in the back, it can make more of a difference than you can imagine. I moved one battery from the back to the front of my 1448, it went from plowing at 11mph to planing nicely at 17mph

Next I would get a tach rigged up, see what RPMs you are running WOT. It might be worthwhile to try a lower pitch prop, since you're running a small motor with a heavy load.


----------



## DaveP (Aug 27, 2018)

GYPSY400 said:


> Why 3 batteries anyhow? I run 2 size 24, one in the back for the electric start and all the boat accessories, and 1 in the front for the bow mount TM.
> 
> Sent from my SM-G903W using Tapatalk



It was rigged that way, two batteries in series for the 12V trolling motor for increased capacity.


----------



## DaveP (Aug 27, 2018)

Pappy said:


> If your running quality is good at idle then your engine is well sealed and you will be wasting money on Seafoam.
> The suggestions on re-distribution of weight are the correct suggestions. With a small boat and limited horsepower it is all about planing surface (area) Your boat is loaded similar to full sized bass boats minus the horsepower. By moving the weight forward you will increase planing surface and your issue will be minimized.
> All you have to do is move the batteries on a temporary basis to verify. After that you can make a permanent choice.



Will give that a shot this week and report back.


----------



## Zum (Aug 27, 2018)

Dave P. "It was rigged that way, two batteries in series for the 12V trolling motor for increased capacity."
Series would be 24v ...parallel would give you 12v and more aH. 
Anyways like others have mentioned, sounds like a lot of weight in the stern. Without a tach , I'd remove the batteries and anything else not necessary and see if the motor /boat performs better.

Sent from my SM-T350 using Tapatalk


----------



## DaveP (Aug 31, 2018)

Quick update after getting out last night. Plugs re-gapped to 030. Got 18-19 mph on the clock now. Tried having someone sit in the front, no major difference. Took tach out and cleaned and reseated all contacts. Changed the dial on the back several times and returned it to the original spot (as recommended). Getting juice, everything works as far as idiot lights and the warning buzzer, but tach still inop. Will be picking up a digital tach to check RPMs. The permanent movement of batteries will be a winter project I think.


----------



## Pappy (Aug 31, 2018)

Okay.........
Having someone sit in the front and noting that there wasn't much difference is a comment I would expect. 
You are asking for help. Proper suggestions were given as to moving weight forward. 
What you did was add weight forward but left all the stern weight.......in the stern. 
Move weight forward is different than adding more weight to the bow. Try it and see what you think. 
As to the tach not functioning? You may have a failed rectifier.


----------



## DaveP (Sep 1, 2018)

Pappy said:


> Okay.........
> Having someone sit in the front and noting that there wasn't much difference is a comment I would expect.
> You are asking for help. Proper suggestions were given as to moving weight forward.
> What you did was add weight forward but left all the stern weight.......in the stern.
> ...



Understood. Will definitely give that a shot as I have the chance. Faria tach, warning lights and buzzer work. Getting power, checked with meter, so it seems that the tach itself is possibly the issue. Digital will be here after the holiday so I can give that a shot as well.


----------



## Pappy (Sep 1, 2018)

No, the tach may not be the issue........
The warning lights and the tach are powered up by a keyed b+ signal and ground. That is working. 
The warning lights are on a chip and designed to test each individual circuit once powered up. That function is also working.
The tach signal is driven off one of the yellow leads on the rectifier. If no signal everything else is still capable of working. Faria tachs are notoriously cheap and it may still be the issue however I have seen more rectifiers fail to supply the tach with a signal. 
If the battery leads have ever been connected or even touched backwards on the starting battery it immediately takes the rectifier out.


----------



## DaveP (Sep 1, 2018)

Pappy said:


> No, the tach may not be the issue........
> The warning lights and the tach are powered up by a keyed b+ signal and ground. That is working.
> The warning lights are on a chip and designed to test each individual circuit once powered up. That function is also working.
> The tach signal is driven off one of the yellow leads on the rectifier. If no signal everything else is still capable of working. Faria tachs are notoriously cheap and it may still be the issue however I have seen more rectifiers fail to supply the tach with a signal.
> If the battery leads have ever been connected or even touched backwards on the starting battery it immediately takes the rectifier out.



Quite possible as the cranking battery has been replaced.


----------



## tinskin (Sep 2, 2018)

Most boats I have had w/o trim run best in the second hole. If you are in the first the motor is tucked under.


----------



## DaveP (Sep 3, 2018)

tinskin said:


> Most boats I have had w/o trim run best in the second hole. If you are in the first the motor is tucked under.


Noted, thanks for the tip!


----------



## DaveP (Sep 3, 2018)

Small update, while I was chasing an electrical issue with the anchor winch I found something important. The electronic winch had a broken negative wire at the terminal where it was attached to a 27 series battery. It was the ONLY thing attached to the third battery. The third battery is now out of the boat.


----------



## turbotodd (Sep 7, 2018)

Don't know how far you venture from shore/ramp, but I only run one battery. I don't see a need for more than one in 99% of the rigs we sell/service/rig/use around here. I think most of us are within 5 miles of shore and on inland lakes and rivers. I could see having 2 if you trolled a LOT but in my case, I do troll some but not a lot...and that single battery will still start the outboard even after trolling for 5+ hours at 1-3 mph with the trolling motor. Yes it cranks a little slower, but it always starts. Besides, the motor's got a backup recoil start-so I'm not scared of running the battery down. Might be beneficial to have two batteries if you were running a long distance and trolling, and or a long distance combined with being in an areas where few others are. That doesn't happen where I am usually fishing. I run a blue top Optima which is lighter than a single 27 series deep cycle, takes up less space too. It's always connected to a trickle charger when parked. Last battery I bought was 1/18/2001 (optima) and I replaced it in 2015, so I do believe that the trickle charger helps battery life.


----------



## DaveP (Sep 8, 2018)

turbotodd said:


> Don't know how far you venture from shore/ramp, but I only run one battery. I don't see a need for more than one in 99% of the rigs we sell/service/rig/use around here. I think most of us are within 5 miles of shore and on inland lakes and rivers. I could see having 2 if you trolled a LOT but in my case, I do troll some but not a lot...and that single battery will still start the outboard even after trolling for 5+ hours at 1-3 mph with the trolling motor. Yes it cranks a little slower, but it always starts. Besides, the motor's got a backup recoil start-so I'm not scared of running the battery down. Might be beneficial to have two batteries if you were running a long distance and trolling, and or a long distance combined with being in an areas where few others are. That doesn't happen where I am usually fishing. I run a blue top Optima which is lighter than a single 27 series deep cycle, takes up less space too. It's always connected to a trickle charger when parked. Last battery I bought was 1/18/2001 (optima) and I replaced it in 2015, so I do believe that the trickle charger helps battery life.



Probably will keep two for the time being. You are right about the trickle charger, I've got an 08 vintage deep cycle still going strong.


----------



## DaveP (Sep 14, 2018)

Finally got out last night for a while after the downpours last weekend. Motor in second hole, less one battery (now two), a little over a half tank of gas and I can get 20-21 mph on the clock. Regulator is on the way to see if that will make the tach operate normally. Re-stuffed the pedestal seats and cut down the protruding mounting bolts, what a difference! Upgraded to a taller front pedestal and it sure helps with the TM foot pedal. Since I'm seldom out all day, I'll look at cutting back to one battery. The only thing that concerns me there is if we run the livewell pumps and upgrade the electronics down the road. I'm very happy with the boat, handles like a dream and is comfy, stable and dry.


----------



## DaveP (Sep 23, 2018)

Installed the new regulator, tach is still inop. So, looking like a bad gauge after all. I'm going to try the wrap a wire around the spark plug wire type tach just to see if I can get a read on the RPMs. Take a look at the prop and see if you think it can be refurbed or just becomes the emergency spare. Looks like it was run on the river since it's pretty knicked up and dull. Don't want to buy new until I know for sure what I need.


----------

