1978 Johnson 75HP 75ELR78C hard to start

[msr64555]

I ran all last year not knowing if my boat was going to start at the ramp or not and it was such a headache/worry that I wouldnt be able to get started. Once the boat is warmed up it usually starts right up in just a few cranks, but starting in the water cold is where I have issues (running on muffs generally isnt a problem to get started). I ran compression last year and it all looked good if I remember correctly. I pulled it out of storage this year and couldnt get it started the first day, came back the next day and got it started by taking off the air intake and shooting a bit of starting fluid in the carbs. I ran it for about 3 or so minutes and the images are what the spark plugs look like after running. Im not too sure how they look so any advice on that would be helpful. I put in a new fuel pump, lines, and primer bulb last year and it didnt seem to help. I can get the bulb hard (I think, I have nothing to compare it to) and it stays hard (not rock hard but can only squeeze it about 1/3 of the way compressed. Carbs were cleaned at the beginning of last year. So that leaves me with spark being the last real question. They guy before me replaced the coils and they look pretty new. Any help is much appreciated!

 

[kevinj]

Those plugs look wet which would point to weak spark. But, let's go through the basics:

1) Compression - What are the exact numbers for each cylinder, not just "they looked good".

2) Spark - Using an air gap tester, with the spark plugs removed, will the lead for each cylinder produce spark that jumps a 3/8" gap? If not, then spark could be your problem

3) Carbs - Yes, they were cleaned, but were the float levels set properly? If the float is too high you could be flooding your engine.

4) Battery - Are all connections clean, tight, and free of corrosion? Is the battery fully charged and shows 12.2volt at rest? Has the battery been load tested? If your battery is weak or you have poor connections the starter won't spin fast enough. The ignition system needs 350RPM to initiate spark. This could explain why it will start on muffs, but when you put the engine in the water the backpressure causes it to spin slower and won't make spark to start.

5) Starting sequence - How exactly are you trying to cold start? Are you using the choke and warm up lever?

 

[msr64555]

Those plugs look wet which would point to weak spark. But, let's go through the basics:

1) Compression - What are the exact numbers for each cylinder, not just "they looked good".

2) Spark - Using an air gap tester, with the spark plugs removed, will the lead for each cylinder produce spark that jumps a 3/8" gap? If not, then spark could be your problem

3) Carbs - Yes, they were cleaned, but were the float levels set properly? If the float is too high you could be flooding your engine.

4) Battery - Are all connections clean, tight, and free of corrosion? Is the battery fully charged and shows 12.2volt at rest? Has the battery been load tested? If your battery is weak or you have poor connections the starter won't spin fast enough. The ignition system needs 350RPM to initiate spark. This could explain why it will start on muffs, but when you put the engine in the water the backpressure causes it to spin slower and won't make spark to start.

5) Starting sequence - How exactly are you trying to cold start? Are you using the choke and warm up lever?

I dont remember the exact numbers for the compression, but I know all 3 cylinders were within a few pounds of each other, and they were around 120-130 psi if I remember correctly. I should get an air gap tester and do that for sure. For the carb floats I can definitely say I am no expert at working on carbs and I am not sure how to properly set the float height, any advice on that would be helpful. Went through pretty much every connection on the engine yesterday and cleaned up all of the contacts with a wire brush. I started it today (on muffs) and had the fastest start I can remember ever having (basically started up as soon as it turned over). Still have to lake test it but fingers crossed that may have been a big contributing factor. My normal starting procedure is to pump the bulb until hard and crank it with the choke on. I do not have a warm up lever on my controls. If I think I have flooded the engine I will disconnect the fuel line at the quick connect and crank it with the throttle advanced to clear it out and then hook fuel back up and prime/try again.

 

[racerone]

Your control box will have a warmup feature.----Find it / learn how to use it.

 

[kevinj]

..... I am not sure how to properly set the float height, any advice on that would be helpful.

Setting float height is done with the carbs removed. Remove the float chamber then hold the carb upside down. The float should be level with the carb body or even just slightly high on the end opposite the hinge pin. I believe there is an exact measurement for how much higher than the body is acceptable, but I've always had success making them exactly level.

Went through pretty much every connection on the engine yesterday and cleaned up all of the contacts with a wire brush. I started it today (on muffs) and had the fastest start I can remember ever having

Good tight connections always help

My normal starting procedure is to pump the bulb until hard and crank it with the choke on. I do not have a warm up lever on my controls. If I think I have flooded the engine I will disconnect the fuel line at the quick connect and crank it with the throttle advanced to clear it out and then hook fuel back up and prime/try again.

If you have side mount controls you will definitely have a warm up lever on the back just above the ignition. If you have recessed controls there should be a button in the middle of the handle that you push which disengages the shift mechanism then you can advance the throttle without putting the engine in gear. Either way, as Racer said, your controls will definitely have a warm up feature.

 

[msr64555]

Thanks for the advice on the carbs. As for the warm up feature, I actually have split controls (1 lever for shifting and 1 lever for throttle) so when I start I usually raise the throttle a bit, which I believe (correct me if I am wrong) is the same thing as a warm up lever.

 

[kevinj]

Thanks for the advice on the carbs. As for the warm up feature, I actually have split controls (1 lever for shifting and 1 lever for throttle) so when I start I usually raise the throttle a bit, which I believe (correct me if I am wrong) is the same thing as a warm up lever.

Yes, with a separate throttle lever, advancing about 1/8 or little more during starting does the same thing as the warm-up lever.

Also, it's worth checking the health of your battery to make sure you're spinning the engine enough to make good spark on those cold starts. When you say it starts easy on muffs, but difficult in the water makes me think the backpressure from the lake is pointing to a weak battery.

 

[racerone]

I suggest you find a single lever control box.---Simple as that.-----Find one with a red plug , used from 73 to 95 models.----Best to get one from say 1980 and newer.