4000 rpm

[Kyletalmadge]

I have a 93 lund with 93 mariner in it. 115hp. I changed out switch box, plugs, stator, trigger and made sure timing was good. Its hitting on all cylinders and runs great but wont go above 4000 rpm. It starts as soon as you turn the key. Boat ran normal last year before stator went out. Anyone know what it could be? All parts are cdi electronics besides a sierra switch box

 

[mgjtkt]

Rebuild the carbs. Check all passages/ jets with a magnifier. You seem to have replaced all the electrical parts.

 

[Kyletalmadge]

Rebuild the carbs. Check all passages/ jets with a magnifier. You seem to have replaced all the electrical parts.

It ran fine before i messed with the electrical stuff is the weird thing. What all should i replace in the carbs?

 

[christopher425]

@Kyletalmadge Did you ever figure out your problem?

 

[Kyletalmadge]

No sir

 

[racerone]

Post compression test values.----Why were all the electrical parts replaced ??----Tachometer checked ?----Water pump impeller replaced ?-----Oil injection tested , if in service ?------Overheat horn tested ?

 

[Kyletalmadge]

Compression is at 130 in all cylinders
Tachometer is probably accurate being boat only does 22 when it used to run about 35. Im pretty sure oiler works. The levels come down. It pees water so never thought i needed to check over heat horn. All electronics were replaced because of bad stator. Boat that old figured you might as well replace them all

 

[racerone]

Some orderly trouble shooting needs to be done.----Does spark jump a gap of at least 3/8" on each lead , yes or no ?---Did you torque flywheel nut to correct value ?----Flywheel key checked ?-----Checked for cylinder sleeve out of position ( rotated ) with scope ?----Replacing parts on a hunch is the wrong way / expensive way !

 

[Kyletalmadge]

I didnt replace them on a hunch. I have a buddy that owns a marine shop and i took it in to him due to it not running at all. It died on me going across the lake and i had to be towed back to the dock. My buddy told me it was the stator after some diagnostic test and told me to replace all the electrical components while im in there. He told me to do it myself so it didnt and told me to order my parts from marineengine.com. i torqued flywheel to manual specs. Key is fine. Have not checked sleeves due to boat running fine before stator went out. Have checked to make sure spark just 3/8s i used a spark tester. Also tested trigger and stator leads with volt meter and they are within spec of cdis specs. The boat will rev about 4k for a few seconds and run right then come back down to 4k. I thought maybe the prop could be aerating but it wont free rev past 4k either but about every once in awile. Change my fuel bulb and fuel line thinking that might be it but now im at a loss

 

[Kyletalmadge]

I bought a manual before performing any work. I always do. I built my own duramax so thought i could handle this.

 

[racerone]

Your buddy with the marine shop should be able to figure it out.

 

[Kyletalmadge]

I just dont have the money for them to diagnose it again. With a new trim assembly, electrical parts and disnosing i have like 4k into it.. not to mention the guy who had it before me had all the electrical messed up. Horn, bilge, Tachometer, speedometer, livewell , nothing worked so he fixed all that. A 6k dollar boat is turning into a 12k dollar boat. My buddy told me to sell it and buy a new one haha

 

[racerone]

He is not your " buddy " I think.------I think it is running on 3 of 4 cylinders.-----Should not be hard to figure out.

 

[Kyletalmadge]

He is not your " buddy " I think.------I think it is running on 3 of 4 cylinders.-----Should not be hard to figure out.

I was thinking the same thing but i put new plugs in and

 

[Kyletalmadge]

I was thinking the same thing but i put new plugs in gapped to .40 like manual said. Checked for spark, they all sparked and after the first day of running it on the lake i brought it back to the shop and checked all the plugs and all 4 were black like there was combustion. Problem is ive always worked on diesels and never gassers. So ive never dealt with spark. Our best boat mechanic here in wyoming also moved to florida. Kinda limited on boat mechanics around here. Im wondering if it couldn't be a carb issue but idk if that would make since when it ran perfectly before the stator went out

 

[brodmann]

Is it possible that with replacing all of the electrical/timing/ignition parts that you need to adjust your WOT timing advance? Does it run smoothly and strong all the way up to 4000 RPM's? If it runs fine up to that point, but doesn't go beyond that, does the cable continue to open carburetors the rest of the way and does the timing seem to continue to advance as you throttle up more?

 

[airshot]

When you removed the old plugs, you should have been able to tell if one wasn't firing, I would think ??

 

[Kyletalmadge]

Is it possible that with replacing all of the electrical/timing/ignition parts that you need to adjust your WOT timing advance? Does it run smoothly and strong all the way up to 4000 RPM's? If it runs fine up to that point, but doesn't go beyond that, does the cable continue to open carburetors the rest of the way and does the timing seem to continue to advance as you throttle up more?

I had the boat shop here check the timing on it after i got done replacing parts. They checked top dead center and the fuel time and said both were spot on. It runs smoothly til 4000 rpm then kinda sputters. The boat mechanics here in wyoming suck

 

[Kyletalmadge]

When you removed the old plugs, you should have been able to tell if one wasn't firing, I would think ??

Yessir.

When you removed the old plugs, you should have been able to tell if one wasn't firing, I would think ??

was thinking the same thing but i put new plugs in gapped to .40 like manual said. Checked for spark, they all sparked and after the first day of running it on the lake i brought it back to the shop and checked all the plugs and all 4 were black like there was combustion. Problem is ive always worked on diesels and never gassers. So ive never dealt with spark. Our best boat mechanic here in wyoming also moved to florida. Kinda limited on boat mechanics around here. Im wondering if it couldn't be a carb issue but idk if that would make since when it ran perfectly before the stator went out

 

[racerone]

Does spark jump a gap of at least 3/8" or more on each lead ?----Use a test device and not the sparkplugs.------Or start motor out on lake. ----Take up to full throttle with #3 plug wire pulled off.----Repeat with #4 and then #1 and #2----Also use a STRONG flashlight and look into each carburetor bore at full throttle.----Compare fuel coming up each nozzle.-----Some simple trouble shooting and thinking finds the issue almost every time !!