Funky smell from engine compartment /5.7 V8 Mercruiser I/O 1993

[Rick Fernandez]

Hello all, I want to first say thanks for always helping out with my other boat issues when needed, all your replies have been very helpful and resolved. My new issue on the boat started last sunday when we had the family on the boat, too many people and I know we were straining the engine, it was stupid of us(overload I believe), never do it again, cruising slow almost at full throttle, but didn't want to push it more, kept it 3/4 trottle. Anyway, as we cruised for about 20 minutes we noticed a funky smell (like rotten eggs, foul) coming from the engine compartment, no smoke, just the smell. Not sure what it can be, since all was running ok before. I know it was like loading 10 people on one horse, the horse can only do so much...like I said it was stupid of us to do, but it was done, never again. What do you think could be causing the smell?? I noticed the battery was very hot when we docked. I don't know if it will smell again without straining the motor with less people on the boat, we'll have to test run. Any suggestion what we damaged or what we should check out?? Please advise! Thanks so much!

 

[Nova II 260]

Re: Funky smell from engine compartment /5.7 V8 Mercruiser I/O 1993

10 people aboard shouldn't have taxed your engine enough to do itself any harm. You may have lugged a little and used alot of fuel. I would look at some periphery for that smell. pumps, blowers, etc.
OLd style selenium rectifiers have a rotten egg smell when they are shorted or over heated. I don't know why you'd have one on the boat, but you didn't say what boat you have or how old it is. I'd scrutinize the charging system, especially since your batt got hot. It too will fume a gassous smell when over charging.

 

[Rick Fernandez]

Re: Funky smell from engine compartment /5.7 V8 Mercruiser I/O 1993

thanks for replying and the advice. It is a 1993 SeaRay, 24ft bowrider..(we had 14 people..my bad, but 7 were kids-light weight). I was also thinking overcharging and the smell could've been the battery fluid getting too hot.
Not sure what selenium rectifiers are like you mentioned, are those part of the exaust sys? what do they look like? I have a Alpha One engine, V8, I/O.
I forgot to mention we also added a Fuel additive that day when we filled up, maybe added to much and caused a smell too?? What do you think? thanks again!

Rick

 

[180shabah]

Re: Funky smell from engine compartment /5.7 V8 Mercruiser I/O 1993

Don't worry about the engine right now. Lets go woth what we know. The battery was hot and you smelled "rotten eggs" - Sulfer.

your battery is full of sulfuric acid.

Pull the battery and the alternator, take them both into your local auto parts store(advance, auto zone etc...) and have them both tested. Sounds like you probably have at least one burned cell in the battery, may or may not be due to a faulty alternator.

 

[Zackman]

Re: Funky smell from engine compartment /5.7 V8 Mercruiser I/O 1993

Rotten Egg smell is usually associated with Hydrogen Sulfide, H2S, which is extremely dangerous. I've never heard of a battery producing H2S, but you may be releasing excessive amounts of sulfur from the battery.

Like Shabah wrote, most likely coming from the battery's sulfuric acid and excessive heat. Sounds like good advise to have the battery and alternator checked before anything else. I would also check the battery ground cable and its connection to the engine block.