115hp only 2500 rpms at wot! Help!

[matt194]

I was looking for some help on an rpm problem. I have a 1979 Evinrude 115hp. I have recently rebuilt the carbs, de-carbed with seafoam, did a link and sync, and checked charging system. All things were don't as the manual says but when I took it out to the lake today I only got 2500 wot. I have this motor on a 14.5 ft. tri-hull glastron. I think this boat should fly at wot but I only get around 25 mph. Can somebody tell me what might be wrong?

Here is a link to my webpage that has pictures of my rig.
http://www.webpages.ttu.edu/matpope/boat.htm

Also when the engine is in the water after running for a little while, you can see a film of oilly stuff on the water. Any ideas?

 

[DJ]

Re: 115hp only 2500 rpms at wot! Help!

Do you have spark on all four cylinders?

 

[matt194]

Re: 115hp only 2500 rpms at wot! Help!

First of all thanks for the quick response.

Before I bought the motor I had it checked out and the mechanic said one of the cylinders didn't have spark but then he messed with it and he finally got it to spark. I am not sure now if they all get spark. How would I check that problem? And if one isn't getting spark is that an expensive problem to fix.

 

[DJ]

Re: 115hp only 2500 rpms at wot! Help!

matt,

The V-4 engine will run just as you describe when you lose one cylinder.

The best way to check spark is with an inductive timing light. Many auto parts stores will lend/rent you one.

Place the inductive lead on each plug wire until you find out which one is not firing. It may only misfire under load (in water, in gear).

Most likely, it is the plug wire or a coil. Neither of which is expensive. You can get coils here on iboats.

 

[HighTrim]

Re: 115hp only 2500 rpms at wot! Help!

The film of oil on the water is normal, welcome to 2 strokes. You could also check your spark with a screw in spark tester if you dont have a timing light. On your motor the spark should jump a 7/16 inch gap easily with a strong blue ZAP!! If there is 1 cylinder not firing, first swap the coils with a known good cylinder, if the problem follows the coil, replace it. Let us know what you find.

 

[ezeke]

Re: 115hp only 2500 rpms at wot! Help!

The 7/16 bright blue spark to test for is best achieved with all of the plugs out. That will tell you if the whole ignition system is functional with no load.

The inductive timing light test will be the test to run with the engine running.

BTW, Some synthetic TCW-3 oils are biodegradable and a good choice for the future.

 

[matt194]

Re: 115hp only 2500 rpms at wot! Help!

I could not rent a inductive timing light but I did pull out the spark plugs and took a picture of them. There are 2 plugs that look like the dirty one and two plugs that look like the clean one. The two that are dirty are on the same side and the two that are clean are on the other side. Does this mean that only two cylinders are firing? How else can I check for spark? Thanks

 

[HighTrim]

Re: 115hp only 2500 rpms at wot! Help!

The inline spark tester that I was referring to is very cheap, I have a few that are worth about 10 bucks each. You will use it as long as you have a boat. It is available at any auto parts store.

 

[HighTrim]

Re: 115hp only 2500 rpms at wot! Help!

Also may want to test the timer base if 1 cylinder isnt firing. It is rare that this is the cause but a possibility none the less. Let us know if you have a multimeter or DVA meter for these tests. If in fact 1 bank is not firing, it is possible , although unlikely, that both coils are shot. If swapping them with the good 2 doesn't improve things, swap the power packs. If still no change you should test the stators resistance. You should read approximately 500 ohms from the brown wire to the brown/yellow wire. Also check the DVA output from the stator. You should have a reading of at least 150V or more from the brown wire to the brown/yellow wire (while connected to the pack). Also check DVA to engine ground from each brown wire and compare the readings. If one wire reads low while connected to the pack, swap the connections and see if the low reading stays on the same stator wire. If it does, the stator is bad.

 

[DJ]

Re: 115hp only 2500 rpms at wot! Help!

Any signs of water droplets on the clean plugs? If so, you have a gasket issue on one head. Not unusual and usually just requires a gasket replacement.

 

[tashasdaddy]

Re: 115hp only 2500 rpms at wot! Help!

you need a service manual: outboardbooks.com make it your best friend. no one has mentioned compression. could be firing and have low compression. could be clogged carb.

 

[matt194]

Re: 115hp only 2500 rpms at wot! Help!

I do have a service manual and a multimeter but I don't know what DVA meter is. I have checked the resistance of the stator a few days ago and it checked out fine. I have rebuilt the carbs and made sure the carbs aren't clogged. I didn't find any water on the clean spark plugs. I've started doing ignition test from the manual but I am a little confused on what leads are supposed to be hooked up when testing the coil. The test says i should be reading 250-300 ohms. Should the battery be completely disconected or can I just unhook the positive side to do the test? I will get the spark tester and let yall know what happens. Also I will do a compression test. Thanks for all the help.

 

[DJ]

Re: 115hp only 2500 rpms at wot! Help!

Don't over diagnose this thing. First is compression. If you don't have that, you have much bigger issues.

Second is spark. It's either there or it isn't.

Clean spark plugs mean one of several things.

1. Water ingestion.

2. No spark.

3. No spark or fuel.

BTW, DVA means: digital volt amp meter.

 

[tashasdaddy]

Re: 115hp only 2500 rpms at wot! Help!

this may help, about 6 pages of test, find the section for your motor.

"http://www.boatpartstore.com/page28.asp"

 

[matt194]

Re: 115hp only 2500 rpms at wot! Help!

I did a compresion test and found that all cylinders were 105 +/- 1. I am happy about that. When I had bought the motor 1 cylinder was low but the mechanic that checked out the boat said it would most likely go up when I decarb the engine. I bought a spark tester from an automotive store but I couldn't see a spark on any cylinder. I tested the spark with all plugs in the cylinders. I could not find a great ground, so could I use the negative terminal of the battery? I uploaded a picture of the tester. Could you tell me if this one will work. On the back of the package it say "works on DIS and HEI electronic ignition systems".

 

[HighTrim]

Re: 115hp only 2500 rpms at wot! Help!

It does not look like it has an adjustable gap that you can set. Although my eyes are poor You should remove the plugs when testing, and your motor should jump a 7/16 of an inch gap. Compression is good.

 

[flabum]

Re: 115hp only 2500 rpms at wot! Help!

That spark checker is sufficient for you checks....if it doesn't jump that gap, you got a problem. Check all the ground connections on the ignition system,,,,,,,, make sure they are all clean and tight.

 

[HighTrim]

Re: 115hp only 2500 rpms at wot! Help!

If you are not getting any fire at all, it could be a number of things.

1. Disconnect the black yellow kill wire and retest. If the engines now has fire, the kill circuit has a fault-possibly the keyswitch, harness or shift switch.
2. Disconnect the yellow wires from the stator to the rectifier and retest. If the engine fires, replace the rectifier.
3. Check the stator resistance. You should read approximately 1000 ohms from the brown wire to the brown/yellow wire and 100 ohms from the orange to orange/black.
4. Check the DVA output from the stator. You should have a reading of at least 150V or more from the brown wire to the brown/yellow wire (while connected to the pack).
5. Check the timer base resistance from the white wire to the blue, green, pink and purple wires. Reading should be 38-42 ohms.
6. Check the DVA output from the timer base. A reading of at least 0.5V or more from the white wire to the blue, green, pink and purple wires (while connected to the pack) is needed to fire the pack.
7. Check the cranking RPM. A cranking speed of less than 250-RPM will not allow the system to fire properly.

 

[matt194]

Re: 115hp only 2500 rpms at wot! Help!

Thanks for all the responses. I have finals until Wednesday, so I will not be able to test the components until then. I will let yall know how the results turn out. thanks again

 

[matt194]

Re: 115hp only 2500 rpms at wot! Help!

I did a spark test. I got spark on all cylinders. I did the test with the spark plugs in but the plugs pulled off of them. Now what should I do?