Mercruiser 5.0 misfiring and taking on water

[bassboy416]

I have an 87 mercruiser 5.0 with a chevy 305. I rebuilt the carb this year after de winterizing and ran the boat 3 times with only minor adjustment issues. This weekend I took it out and I noticed at first it would intermittently not get on plane right away at WOT. After fishing at idle for a while, I went to take off and it seemed as if it was totally loaded up and wouldn't get on plane. I wasn't incredibly concerned about this, except on the way to the dock to pick up a passenger it started misfiring and running really poorly driving at about 10 mph at wot and shaking and occasionally backfiring. It would idle perfect, and rev in nuetral perfect. After picking up the passenger it continued to deteriorate. The passenger claimed to know how to adjust the carb, so we messed with the adjustments on the carb noticing very little difference at wide open throttle. It just wasn't making much of a difference. Then, watching the motor while in gear at WOT I noticed three spots up high on the back of the motor spitting out water pretty bad. It didn't look like it was cracked it almost looked as iif there were three factory holes there. I also began to notice a very large stream in the front (under the pulleys) at the very bottom of the motor. At this point the motor would not even try to start. It would only crank without any sputter or sign it was even trying. The boat filled up with a ton of water and the bilge couldn't keep up. I started bailing by hand and barely kept even. What could I possibly be looking at here? the boat has run great for years without any issues, I have no idea if these are related or not. I was assuming fuel or electrical until I noticed the water. now I have no idea. Thank you ahead of time.

 

[Bt Doctur]

the water stream under the front pully could be the ps cooler that may be cracked ,
watching the motor while in gear at WOT I noticed three spots up high on the back of the motor spitting out water pretty bad. It didn't look like it was cracked it almost looked as iif there were three factory holes there

There are no cooling plugs that high, you`ll have to narrow it down a bit more

 

[tpenfield]

I would check all of the core plugs. Check the oil to see if it is milky.

Were you getting pure water in the bilge or was there oil mixed in?

 

[Scott Danforth]

any chance the plugs were not put back in after winterization?

 

[bassboy416]

Thank you for your help. When I winterized it, I ran rv antifreeze through the ears until the fluid was coming out of the outdrive. I have had it out 3 times since and not noticed the leak until yesterday. As far as the 3 places water was coming out I know that is very vague I wish I would have taken pictures. The best description I can give without taking pictures is they are on the side opposite of the pulleys toward the top of the engine and are in a triangular pattern. It was more of a mist coming from that area so maybe I am mistaken and it was just spray from elsewhere. Unfortunately I did not have the wherewithal to investigate further when I was on the water. As for the water in the boat, no I did not notice any oil in it. As for the oil, I did check it and it is very fresh oil. I could not tell if the consistency was normal but it was not milky whatsoever it looked very clean. could there still be traces of water in there? I called a mobile mechanic who helped me with the outdrive last year and the suggestion I got from him was to remove the rear seat and basically deconstruct everything in the way of the motor (rear seat, side compartments, carpeting and all. He said that once we had clear access to the motor, the problem should be obvious. this is on a 1987 invader. The interior is totally shot and until now it has always run fantastic. I put a good chunk of change into the outdrive last year with new bellows, gimbal bearing, u joint(s). This year, the exhaust bellows came loose and I was told that it was not an issue and if anything may improve horsepower. I'm not sure how far I'm even willing to go with this, but since the interior is shot, maybe deconstructing the back seat will give me an opportunity to build a bench I could purchase cushions for... I'm at a loss... anyway, heres another detail I may have forgot to mention... last year, I rebuilt the carb and the boat ran better than ever... it sat for 3 months then wouldn't idle properly.... I rebuilt the carb again this year thinking it was dirty and had the same problem, so I raised the idle slightly and adjusted the carb until it ran at idle and full throttle however at idle it would lope. when I purchased it, it had water in the fuel tank and i pumped the tank and replaced fuel water seperator (3 times since then). The last time I rebuilt the carb I noticed water under the carb. The gas cap (which is inches above water) has always been missing and I've never been able to find the proper size, so I've always had oakie rigged gas caps... Not sure if any of this info will help, but I'm inclined to head down to storage and deconstruct the back end so that I can get a look at the motor. If any of you would follow my thread I'd be happy to run any tests and take pictures to bring back here... These iboats forums have been a blessing to me for years, and I truly appreciate your help. I apologize for my lack of knowledge and admitted ignorance regarding mechanical common sense. I realize that the gas cap situation is completely unacceptable and that running the boat when the carb is out of adjustment can cause damage... I do have compression testers and what not.... what gets me is that right before it died, it actually had a brief moment where it planed out and drove normal for about 15 minutes.... I'd love if I could salvage this boat. but prepared to turn the page.

 

[JASinIL2006]

Thank you for your help. When I winterized it, I ran rv antifreeze through the ears until the fluid was coming out of the outdrive.

Did you drain the block as well, or just run the antifreeze through the muffs?

 

[Rick Stephens]

I couldn't tell where on the motor that triangular pattern of spray was from. Maybe you can describe it a bit clearer. At first I thought you meant from behind the motor and I was zoning in on transom area. But later I got the idea you mean high up on the front of the motor?

Your running problem sounds like an ignition issue more than carburetor to me. Loose timing, worn advance plate, carbon inside the cap.... something like that.

Rick

 

[Bondo]

When I winterized it, I ran rv antifreeze through the ears until the fluid was coming out of the outdrive.

Ayuh,..... If ya didn't Drain the block, Before ya did this,.....

At Best, ya mighta winterized the exhaust manifolds,....

Certainly not the motor, the T-stat would be closed,....

 

[Scott Danforth]

^+1

agreed. you could run 50000 gallons of anti-freeze thru the motor, however it will all go out the exhaust until the T-stat opens. BTW, the T-stat will open after about 10 minutes of operation, which is about 2000 gallons of water thru the pump