Need some advise on my 6hp johnson

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BassmanET

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So, I was given a 6 hp 67' Johnson. It runs good & pushes my 1436 jon ok? But, it doesn't seem to running 100%, in other words it doesn't seem to put out 6hp? After seeing some videos on youtube of a 6hp on a 1436 jon (empty , just 1 person & motor) it is getting up on plane & doing about 12-14 mph. Also, after calling my local repair shop, was told that a 6hp should get up on plane with on person in the boat. My motor does not do this, I get about 6.5 mph.

Here's what I know about the motor, it had compression test & read 70 psi. Spark plugs are good Seafoam the engine as well. Starts up & stays running no problem.

So, am I expecting too much out this little motor or is something wrong with?
Fish sometimes alone or with one of my kids. So, 6hp is fine with me if it can do 12-14 mph.

So, my dilemma is. Do I bring it to the repair shop spend $100-150 to find out what's wrong & fix.
Or, sell it & upgrade to a 9.5hp? Here's a video from youtube of the boat & motor,

https://www.youtube.com/watch?v=k12I9xnWknw
 
What is the hull weight of your boat and what is max hp rating? 6hp seems a little small to me for a 14ft boat. Also 70lbs compression sounds low.
 
I think you may be slightly underpowered at less than half the rated hp even though that's a fairly light hull. A 9.9 would make a lot of difference.
 
The issue may be a little bit of everything here. 70# compression is not stellar by any means but that is just one compression gauge reading.
The fact that the boat is a 1436 means that it is quite narrow. That engine on a much wider 14' hull may actually outperform the 1436. Small engines like lightweight boats with a good amount of lifting surface under them. Hull loading is everything with smaller engines.
I had a 1236 years and years ago. Would plane off with my small son, fuel tank, fishing gear, small cooler and I in it with a 1957 7 1/2hp on it...... but just barely. Went to a good wide 14' V-bottom and increased performance all the way around.
You may be happier with a larger engine on that particular boat.
 
Here's what I'm it comparing too

This is 1436 jon but it empty no gear or anything.
https://www.youtube.com/watch?v=zQQuLX1I0gw

This is also a 1436 loaded up 1 adult & 2 kids.
https://www.youtube.com/watch?v=t3bgw8tiB-w

Not what I'm getting out my motor?
 
Pappy said:
Okay....lets see then.
Long shaft engine on a short shaft transom?
Worn out propeller?
Carburetor not fully opening
Wrong tilt pin location.
Incorrect weight placement?
Number 3 a possibility. In his video it didn't sound like his rpm's were as high as they should be. But that could also be due to low compression.
 
Short shaft
Prop looks ok
Carb but sure about
Pin location is good
Weight had battery, trolling motor in back. But that willbe moved up front.
 
Pin location should be all the way against the transom on your set up.
You have a bunch of extra weight in your hull compared to the other videos you compare against.
Move weight forward and try your speed runs again. You are still running bow high...gotta get that bow down and fully on plane.

On the carb look at the throttle shaft that passes horizontally through the carburetor. Looking at the left or stbd side of the carb you will see a roll pin that goes through the throttle shaft. That pin, at WOT, should be close to vertical. If you have a worn or grooved throttle roller you may not be opening the carb fully.
 
Pappy said:
Pin location should be all the way against the transom on your set up.
You have a bunch of extra weight in your hull compared to the other videos you compare against.
Move weight forward and try your speed runs again. You are still running bow high...gotta get that bow down and fully on plane.

On the carb look at the throttle shaft that passes horizontally through the carburetor. Looking at the left or stbd side of the carb you will see a roll pin that goes through the throttle shaft. That pin, at WOT, should be close to vertical. If you have a worn or grooved throttle roller you may not be opening the carb fully.

The battery got moved up behind the front pedestal seat & trolling motor I mounted on the bow today.
I'll check the throttle too. That was my second run with the pin in the middle, first run was all the way against the transom like you said but, didn't make a difference. But, I'll it again.

Be heading out this weekend, I'll let you know how it goes! Thanks for the help!! :wink:
 
Did you test the compression yourself? I would check again in both cylinders. Back to your original question. If you got the motor for free I would consider spending the money to get it checked out. Ask them to check the compression before doing anything. Even if it costs 200.00 to fix it you are ahead. If it still isn't enough for your boat you can sell it and get your money back.
 
Tallpine said:
Did you test the compression yourself? I would check again in both cylinders. Back to your original question. If you got the motor for free I would consider spending the money to get it checked out. Ask them to check the compression before doing anything. Even if it costs 200.00 to fix it you are ahead. If it still isn't enough for your boat you can sell it and get your money back.

No, my employee who is also a Mechanic checked it for me.
Good point on if I fix it & decide to sell it.
 
Got the diagnosis today from the repair shop.
Says, cleaned the carbs, changed the gear case oil (which was really bad & may have a leak) & has it running. Next he says, that its over heating. Pump is working ok & could be the thermostat ?
So, I'll be heading over to pick it up Friday. We will then run it in the shop, so I can see it myself.

Any comments or suggestion? Not really familiar with these motor?
 
70psi sounds really really low - though I haven't tested my old 55 johnson to see what the compression is, maybe that's normal for the old aluminum engines, I tend to doubt it.

Normal pump gas runs on ~8.7 -> 9.3 to 1 compression - that's usually a range of ~100 psi to ~130 psi, 70 is way outside that range to the point I think you'd have combustion issues for sure. To answer your question why you might not have proper compression? Probably best case scenario would be loose spark plug(s)...next up probably blown head gasket (bit more work, still easy enough to fix), worst case would be cracking somewhere.

Hard to compare your boat with whatever wood weight you have to the ones in those videos, other than to see your motor isn't running properly, but you knew that already. Bottom line with 1 person it should plane.

Does it rev up in neutral and not when it's in gear?

If you remove a plug after running it are the plugs noticeably wet with gas?
 
My last outing the motor wouldn't run?
But, last successful run. Yes, seemed to reve good.
Mechanic cleaned up & has it running.
I'll give another test run?
 

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