[agt72451]

To all of the members, HELLO. My name is Alo, reside in Pa. and am a retired disabled veteran. I have a Mariah 20' I/O w/ six cly. Merc. I am hoping that someone with more knowledge than me can help me or direct where to look.
The problem I am having is as follows along with procedures already done. From the day I purchased the boat, the same problem keeps me land-bound instead of on the water so any suggestions will help.
When we first start up and start running, it seems fine for about 1/2 hr. and then it starts shutting
down and we need to wait about 20 to 30 min. to start and get going but it will not maintain any speed. We had a brand new carb installed as well as new battery & start.Result, about the same with the exception of being able to maintain a steady slow pace(thank God cause rowing is not the way to go).
Someone suggested that it may be the coil is bad and believes that after running it, the coil could heat up and shut it down.My hope is that either someone has had this problem and make suggestions on how to proceed? The boat is excellent shape other than. Please send any suggestions to my address. Thanking in advance anyone who can help.

Sincerely
Al Troutman

[SEMIJim]

Welcome to the MOC, Al.

Sorry to hear of your boat troubles.

There are two or three ways you can proceed. The easiest, and most expensive, probably, is to hire a certified MerCruiser mechanic to fix your boat. A possibly cheaper route would be to hire any old mechanic who's cheap. A possibly even cheaper route would be to learn your boat's engine, and how it works, and fix it yourself.

You'll note that the above has lots of "probably"s and "possibly"s. That's because there are too many variables to know. For example: The cheap any-old-mechanic or you could get lucky and it's an easy fix. On the other hand: It could be a tricky problem to diagnose, so the certified Merc mechanic could be way cheaper, in the long run.

One thing is almost certain: Trying to troubleshoot this over the Internet is going to be neither quick nor cheap. There are just too many components in a MerCruiser engine the malfunctioning of which could result in the symptoms you describe. The coil is indeed a suspect. So is just about the entire rest of the ignition system, including, and perhaps even primarily, the very expensive Thunderbolt ignition module. (Assuming you have one.)

I would not have replaced carburetor, starter or battery, given the symptoms you describe.

Jim

[mikeyt]

Welcome aboard Al ! +1 on what Jim recommended. And yes, the coil is a likely suspect.