overheated motor, now what???

[rasbury]

Well, trying to do the right thing really messed me up...at least the method did. Was going on a week long boating trip and have a friend that is a cert. mercuruser mechanic...had just bought my tahoe 3.0, supposed to have only 20 hours on it but I had no idea what maintenance had been done....we changed the impeller and engine oil/foot oil but did not test it. Put it in the water the next weekend and should have paid more attention but the water tube was not all lined up and it overheated pretty good.....I shut it down as quick as I could but it was really a smokin, smelled like burnt rubber. Anyway, we pulled the foot and corrected and it runs fine, no knocking or apparant engine damage thankfully.We checked to make sure water was not now getting into the foot. I did notice, pulling my prop off after my tirp(different story but I have a handle on that), the exhaust tube/bellows split and must have been what I smelled. Also, when we pulled the foot off, there was a nasty pc. of rubber that looked like a flap but he said not to worry. Anyway, I suppose it must be a back flow flap so water does not go back up the exhaust when the motor is not running? Anyway, I searched the forums and not sure I understand between the posts if the out drive has to come off for that bellows or not....for the out drive it seems so but not sure on this one.....also, I saw a previous post where someone had the service manual....2007 3.0L, but I can't seem to find it again...anyone know where that's at?
My boat trip went fine, no problems, to Cayo Costa which is boat in only, very cool! (SW coast of Fl)

 

[ziggy]

Re: overheated motor, now what???

we changed the impeller and engine oil/foot oil but did not test it.

imho & fwiw, anytime ya separate the halves, ya should pressure test the drive after it's reassembled + test at home on the hose to be sure water is flowing (exiting) the proper places. ie, prop hub, pee hole if ya got one, idle relief ports. this prevents your scenario..

We checked to make sure water was not now getting into the foot.

how did ya do that? a pressure test?

I did notice, pulling my prop off after my tirp(different story but I have a handle on that), the exhaust tube/bellows split and must have been what I smelled.

if your talking about the exhaust bellows that's just below the drive shaft bellows. it can be removed w/o major ramifications. i doubt that's what smelled as it's underwater all the time + filled with water when static. i would be worried about the exhaust bellows that goes between the riser and the exhaust pipe though. but that's inside the engine compartment.

Also, when we pulled the foot off, there was a nasty pc. of rubber that looked like a flap but he said not to worry.

not to worry ay? well, could be but i doubt mercruiser just put in a water shutter for fun. as stated, it's your water shutter, flappers. like you said, they prevent water from backing up the exhaust system. w/o them, a sudden deceleration wave, following waves, waves that force water up the exhaust when your beached, rev. can push water up to the flappers. they're usually located at the top of the exhaust pipe. inside the boat.

Anyway, I searched the forums and not sure I understand between the posts if the out drive has to come off for that bellows or not.

if your talking the exhaust bellows below the drive shaft bellows between the drive and the gimble housing. then yes. there's a special tool that's used to stretch them out so you can mount the free end to the bell housing. or ya may be able to use an exhaust tube. which i believe was designed for the bravo drive, but works for alpha1 too. research that to be sure.

do did you back flush your cooling system to go find the impeller pieces that broke off and flowed up stream towards your engine. thermostat is a likely place for them to lodge at. find as many pieces as possible, they get into your cooling system in your block and i don't know what ya do to relieve that kind of restriction. basically, ya need to be sure your rubber parts are intact from water pump to flappers.

for the s/m, go look here ,look under mercruiser info, #10..

ya might wanna do a compression test to find out where ya stand after the overheat.

 

[rasbury]

Re: overheated motor, now what???

Well, that was a lot to digest and I did a little digging and looking before I replied, lot's of good info and I thank you for taking the time to respond! I see I should complet my profile so it shows what boat I have etc......It's a "new" 2007 Tahoe 135hp 3.0L by tracker marine with the alpha one out drive. It was bank owned and must have gone through an auction ending up on a dealer lot here in Sanford Fl and I bought it from a guy that had it two months. It still has the factory warranty through Aug. next summer and what ever ave. I go down, I want to make sure I don't trash the warranty. Perhaps the only thing that would make sense now is take it to a dealer but I can only imagine the bending over I'd get for this dumb mistake~! Anyway, my boat working on experience is limited to a 150 HP out board which I rebuilt in a tent in my back yard 20 years ago. I'm pretty handy but not trained and if I can find a manual that says do this , do that, I can generally follow it and recognize problems along the way, good mechanical understanding I guess...

I looked at the boat in a litte more detail armed with a little more info. I pulled the engine cover and looked at the exhaust components. Looks like most of the tubing out of the exhaust to the bottom of the boat is composite or metal types of materials and there is no visable damage to them or surronding compents in the engine compartment. I'm curious where the flapper pc. came out of. When the boat overheated, smoke was so heavy I was grabbing for the fire extinguisher. I should also add to address several of the other "things I should check", for better or worse, I went on a week long boating trip on the west coast of Fl. where the only transportation for the week was the boat- I ran 30 gallons of gas through it with no issues- it ran fine, it warmed up properely etc. You'd never know anything had happened so I'm going to assume for right now the impeller is ok and the cooling system is not in jeapordy. I looked at the exhaust bellows and not only did it split, it's trashed! It split in several places. Looking at the main bellows for the lower unit and I guess what must be protector on the shift linkege, whatever, all of that looks fine, it's all soft and plyable. To bad I'm not a speller. Anyway, the only damage I see is that bellows itself and what ever is damaged in line above there that I can't see. The manual listed is an installation manual and really does not show anything about the assembly of all this stuff- I really need a repair manual as you don't always take things apart the way you put them together if that makes sense....I don't see anyway to get the bellows attached on the boat side even if I pulled the lower unit off! Really tight in there.....So, to understand things to the next level, I need a little better explanation of the exhaust system pcs and detail of "how to" remove the necessary componts to change the bellows as I think I want to keep it orgional rather than some other tube added- not sold on that but I like to keep things the way they were designed. Is there publications on this site similar to the install manuals that are more along the lines of repair or am I not seeing them where I was referred to? I tried the file sharing site linked but got garble when it downloaded....

Thanks
Rick

 

[rasbury]

Re: overheated motor, now what???

well, a little update...after a few days of not being able to get at it, I got at it...lower part of the exhaust hose no problem, man the upper part sure is hard to get a screwdriver on, even with most of the hose tore off! I'll get back to that..pulled the upper exhaust pc. off the top, pulled the intermediate exhaust tube to see where the flap went and it's pretty empty in there...there is like a bar running accross side to side where I guess the flap asembly rests on? I'll be down to the parts store or check on this site for the parts...not to familiar yet what all is offered here. Still wondering if I should pull the lower unit again and replace the water pump AGAIN which is what started all this...it did run fine for a week with no sign of any heat issues etc.....the upper rubber connecter on the exhaust is pretty cooked also, looks like it would still work but I'll see how much it is and replace it probably...

 

[Greytfun]

Re: overheated motor, now what???

Been there, done this (LOL.. now). Your exhaust flappers are history and NEED to be replaced. Great time to do it since you have to replace the upper exhaust bellows anyway. You will most likely find the remnants somewhere down line, i.e. upper or lower unit. There are two (2) flaps that are metal surrounded with rubber. The rubber may be burned off now. I found mine, one in the upper unit, the other at the bottom of the lower unit.

Check ALL the parts of the impeller and housing unit. Lots of plastic that burns up when overheated. The lower exhaust bellows are terrible to replace without the "tool." I've gone through two this year and I'm switching over to the open bellows style. For some reason Mercruiser won't extend the bellows a few inches to make installation easier and relieve the stress when the drive is up for trailering/storage.

Hope this helps a bit

 

[WILSONS88]

Re: overheated motor, now what???

You may have ruined the lower shift cable as well. The heat, if it got that hot could damage the sheath on the cable making it stiff. That would cause the engine to die when shifting out of gear.