2002 3.0 Merc not running on water

[rkr0017]

Good afternoon all! looking for a little insight or a lot of it. I'm pretty new to boating so I apologize in advance if my terminology is off a bit and sorry for the long winded post but I feel like its best if I put the whole story out there.

Just bought a 2002 Maxum 1800 SR last summer. It ran pretty good 5-6 times I took it on the lake. One day in the late summer I took it out warmed it up and backed it out of the dock area, threw it in forward and got to cruising speed once I hit about half throttle it died. I could not get it started again after that. The season was almost over so I got towed in and took it to a garage where they rebuilt the carb and winterized it. (it apparently ran at that time with the hose hooked up to it).
This spring when I took the cover off apparently I had water frozen down by the engine. when it thawed out I looked everything over but nothing at face value appeared damaged. I was having a hard time getting it running after that, basically it would start but not stay running. So I took it back to the garage, they found a fitting near the top of the gas tank was cracked so I was thinking water got in there. They "drained" water out added some dry gas and got it running. They said it ran for about an hour no issues, I took it back to my house, then hooked the water hose up and tried it myself, It started right up and ran for a solid 20 minutes in neutral, forward and reverse under various throttle positions....so now I'm pretty confident.
I take it to the lake start it up with the trailer in the water its running (wonderful!) I back it off and warm it up another couple minutes then throw it in forward and head out, I get to around half throttle seems to be running perfect then all of a sudden it dies right out.... (now I'm f'in pissed). So I towed into a dock on the local lake that repairs boats.....Ill try this. So they tell me theres a ton of water in my gas... so they drain the tank, put more gas in and some extra dry gas for whatever water is left oh and also clean the carb and reset the floats (for a bill of $600 fml). whatever as long as it runs now right? WRONG.
I go to pick it up they are confident in their work, I back it out in to the bay with the mechanic in the boat, takes a little time to warm up and again went from reverse to neutral to forward, this time as soon as he puts it in forward it dies... now it wont start again...... guys I am lost and its becoming a money pit. any help would be greatly appreciated. hopefully someone reads all of this

[Phillbo]

Does it have a fuel/water separator? If so, has it been replaced? If not you may look to add one.


"It started right up and ran for a solid 20 minutes in neutral, forward and reverse under various throttle positions.."

I don't think it's a good idea to engage the outdrive and run it at high RPM's while on the muffs...

[jrsick]

Your problem could be from several sources and you will need to do some troubleshooting.
I've seen these same symptoms caused by a poorly vented gas tank, a cracked distributor cap, and an overheated ICM.
I recommend you download manual #26 in the documents section. See pages 1C12 to 1C17 for troubleshooting your ignition. Complete this checklist and you will know if problem is ignition related, or not.
If you need help in examining ignition components, see the Cleaning and Inspection section of the manual on page 4B6.
Carb rebuilds have 50/50 success rate and I would not assume the carb is good. See section 5B of the manual for complete discussion and checks for the carb.
Your mechanics are stumped and now throwing parts at the problem. I would not rely on them. Let us know where you need help.

[mmwjr]

First a test out of the water tells you very little as there is no load on the engine so a 20 minute run is just wasting fuel.

Since there was a lot of water in the fuel tank the fuel flits needs to be replaced and the carb should be rebuilt. There is probably water in the carbs bowl.

A good tune up is never a bad thing since you don’t know when it was last done.

Sounds like you bought someone else’s problem.

[rkr0017]

I originally thought it was a poor ventilation issue, I cleaned out the vent which had a ton of debris in it, i'm guessing a small animal made it a winter home.
Now ive trouble shot a lot of basic things myself, (cleaned vent, added a check value on the gas line going to the engine and electric fuel pump)I've been working on cars for years but this boat has me stumped and its a pain to get it running and seems to be fine at home just to take it to the launch fight through droves of people and stall out right off the dock. "break out another thousand" is about the truest statement Ive learned in the boating industry.
anyway...before the latest break down I had the garage install a water separator as well. Though this was before the tank was fully drained so it shot that pretty quick

[jrsick]

I"ll second Mike's suggestion to do a tune up. New plugs, cap and rotor at a minimum. The condition of the plugs may help you understand what's happening.
The next time the boat stalls, check for spark. If you're getting good spark then you can move to fuel and compression. I rec getting an HEI tester. The one I have looks like a spark plug and is great for testing spark from the plug wires or coil. You should also check your plugs to see if they are dry or wet-fouled.

[rkr0017]

Alright thanks for the input everyone, I’ll keep you up to date on any new progress, if it still doesn’t run I’ll paddle out to the middle of the lake, pull the plug and go down with the ship like a man haha