'77 merc 1500 lacking power

[monk-monk]

My '77 merc 1500 seems to be lacking power. I started my topic in the prop section because i thought it was an issue with prop being too big. The people that replied to my post indicated my prop size was correct (13 3/4 dia X 19pitch) and they all feel like my motor is down on power. I did a compression test today, readings are as follows: 125, 123, 124, 130, 130 and 125....so i know my compression is good! I removed the plug wires and observed the end that plugs onto the spark plug...all ends of plug wires were either rusty looking, or black looking...i installed another set of wires that appear to be in good condition..that made the motor sound a little bit stronger, but i won't know the outcome until i get it on the water! So, here's where i am at now: with the compression numbers all good, if i am lacking power, it has to be "fire" or "fuel"...What type of spark gap tester should i purchase to verify a strong spark at each plug, and if i wanted to install all new plug wires, where can i purchase a new set? BTW, when i removed the spark plugs, it looks like the plugs are barely firing..the electrode ends of plugs show very little color. I do not see any water spots on them, they smell like gas when i removed them

 

[monk-monk]

...the center electrode on the spark plugs is black in color, but the porcelain around the electrode shows no color (pure white)...#1 cylinder spark plug does have a brown color on the porcelain around electrode, but the rest of the plugs just look like they weren't firing good...they have gas on them, i could see it and smell it...the plugs do not appear to be getting "steam" cleaned from water intrusion...i looked in the cylinders at the piston domes and i see wet carbon

 

[monk-monk]

Mmm..and now i am wondering about these clean spark plugs...if i had water intrusion, would the center electrode be sooty black or completely clean looking? The only spark plug that shows signs of color on the electrode porcelain is #1 cylinder

 

[Chris1956]

Normally, water intrusion would clean the whole spark plug. Also, only a couple of cylinders will have water intrusion, or the motor wouldn't run. Run her some more and then reinspect the spark plugs. The story may be clearer. Look for corrosion spots on the rim of the plugs, and well as water droplets.

 

[monk-monk]

Bump here! I want to eliminate any possible ignition problems. I want to install new plug wires. Does anybody sell pre-made sets (with the screw terminal crimped in place)...if not, what tool is used to crimp on the screw terminal ends?

 

[Chris1956]

You can buy the original "Tiger tails" with the screw terminals installed. You will need to install the spring connectors and boots yourself. They were about $6 each (very good price) at the oldmercs or vintagemercs web site (I forget which). They will be 36" long, and can be cut for custom fit.

 

[Faztbullet]

readings are as follows: 125, 123, 124, 130, 130 and 125....so i know my compression is good!

That just shows they are equal but your bcompression is at minimum as this motor came from factory with high dome piston and compression was at 150psi. Yes it will run at these lower compressions but will be low on top end power and hole shot. Remember you have to realize this is not a prop rate motor and yoy will be lucky to be pushing 100hp at prop...