Mercruiser MCM 170 - stalling and now not starting...

[boater_bill]

Hi everyone
I'm glad I joined this forum and hopefully I can get some help resolving my boat issues.
I bought a 1989 18' sea ray bowrider with a 170hp Mercruiser I/O engine (model MCM 170)
When i first got the boat I changed the I/O oil, fuel filter, spark plugs, and had to change the starter because the old one was jamming (actually I had it rebuilt)
My issues are:
Whenever it's been running for a while (1-2 hrs) it would start to have trouble taking off, meaning that whenever I push the throttle before it hits 1500rpm it would choke out and die. The only way to take off is to push the throttle very, VERY slowly until it reaches 1500rpm and then I can accelerate but if I do it even a little faster the rpm drops and it chokes. The strange part is that this only happens after its been running for an hour or so. This sounds like a fuel issue to me, but i'm not sure, what do you guys think?
Also, another strange thing I noticed is when I put premium 91 octane in the tank, this problem gets worse, but when I put mid-grade 89, its still there but not as bad...
My other main issue just happened a few days ago when I took the boat out on the lake. It was having the same problem as mentioned above, but then it wouldn't start at all (I think I may have drained the battery trying to get it started) and every time I got it to start it would choke on me right away. I tried throttling it to the max but it would still choke. Now that it was clear that my battery was dead, I asked for a boost from a nearby boat. I took their battery and started my engine with it just fine, and after it warmed up a bit I went to switch my battery back in. But as soon as I disconnected the positive from the battery the engine started smoking! So I shut it off, put my battery back in and tried again. I got it to start but it started smoking again. I traced the smoke back to the alternator...Did I do something wrong? What should I do now?
Also when I brought it to a marina for a look, it was brought to my attention that the fuse breaker was bypassed for some reason and that there might be a story behind that...What might be the reason for that?

Thank you for taking the time to read and reply to this post. Your help and support is greatly appreciated!

Regards,

Boater Bill

 

[alldodge]

Hi everyone
I'm glad I joined this forum and hopefully I can get some help resolving my boat issues.
I bought a 18' sea ray bowrider with a 170hp Mercruiser I/O engine (model MCM 170)
When i first got the boat I changed the I/O oil, fuel filter, spark plugs, and had to change the starter because the old one was jamming (actually I had it rebuilt)
My issues are:
Whenever it's been running for a while (1-2 hrs) it would start to have trouble taking off, meaning that whenever I push the throttle before it hits 1500rpm it would choke out and die. The only way to take off is to push the throttle very, VERY slowly until it reaches 1500rpm and then I can accelerate but if I do it even a little faster the rpm drops and it chokes. The strange part is that this only happens after its been running for an hour or so. This sounds like a fuel issue to me, but i'm not sure, what do you guys think?
Also, another strange thing I noticed is when I put premium 91 octane in the tank, this problem gets worse, but when I put mid-grade 89, its still there but not as bad...
My other main issue just happened a few days ago when I took the boat out on the lake. It was having the same problem as mentioned above, but then it wouldn't start at all (I think I may have drained the battery trying to get it started) and every time I got it to start it would choke on me right away. I tried throttling it to the max but it would still choke. Now that it was clear that my battery was dead, I asked for a boost from a nearby boat. I took their battery and started my engine with it just fine, and after it warmed up a bit I went to switch my battery back in. But as soon as I disconnected the positive from the battery the engine started smoking! So I shut it off, put my battery back in and tried again. I got it to start but it started smoking again. I traced the smoke back to the alternator...Did I do something wrong? What should I do now?
Also when I brought it to a marina for a look, it was brought to my attention that the fuse breaker was bypassed for some reason and that there might be a story behind that...What might be the reason for that?

Thank you for taking the time to read and reply to this post. Your help and support is greatly appreciated!

Regards,

Alex

:welcome: to iboats Alex

Appears the PO had an issue with something and that issue kept popping the breaker. You did nothing wrong from your posting as I can see but the PO appears to have done just that. From my take the alternator started having issues and was popping the breaker so it was by passed. Later the ALT reduced the voltage from the battery due to a heavy drain and caused the engine problems in starting. Go have the ALT repaired and reinstall. Remove the by pass from the breaker and let us know what your results are

 

[boater_bill]

Thanks for your help I'll get right on that and I will let you know the results.