Engine wont start when hot

[rludtke]

I actually had issues that sounded just like yours when I first bought my boat (I even had to get towed by my Dad too). My troubleshooting led me to replace the battery because it didn't pass a load test, I discovered badly corroded positive and negative battery cables, I threw an overhaul kit in my carburetor (which bought me additional time, but didn't end my troubles for good, as my carburetor is starting to act up again), and I added an insulator plate between the carburetor and manifold (to isolate the carburetor from the engines heat to prevent vapor lock). I also added a wedge under my carburetor, as I was having trouble getting the float levels right ( the dang thing would not stop flooding). I was thinking that the engine/carb angle was contributing. I don't know if this contributed to the solution or not, as I made many changes at once, but it may have helped.

These tow boats have a pretty rough ride, which I think takes it's toll on some of the more sensitive components such as the carburetor and the battery.

The hard starting may be attributed to carburetor tuning, and/or vapor lock (discussed in other thread). Possibly it is flooding due to the state of tune? You could rules this out by examining the carburetor throat when the condition exists for excess fuel. Mine would drip and sometimes poor fuel out the J vents. Sometimes the front, and sometimes the rear. This may have been due to a needle valve stuck open, but changing the needle and seat wouldn't always fix it. Sometimes adjusting the float level downward was needed to get it to stop. Cranking the engine with the throttle set to full open will allow additional air to help lean the mixture, clearing the excess fuel, and perhaps get the engine started if it isn't flooded to bad, and the trouble is only transient in nature (be ready to pull the throttle back quickly to idle when she lights). I occasionally need to replace parts in my float bowls, and adjust my floats to keep my carburetor operating right- it likes to run rich and flood. It might be time to replace your carburetor. I know I am in the same boat (excuse the pun).

The battery may have a shorted or partially shorted cell. The hard pounding ride may be churning the lead sulfites up off of the bottom of the battery cell, allowing them to get caught between the + and - electrical plates, causing a short. This renders the shorted cell ineffective, causing the battery to "run down" quicker than you would normally expect, or fail to crank the engine after listening to the stereo for a while.

Take your battery to a shop or an auto parts store to be load tested. They could tell you right away if all cells are at full strength or not. In my experience, there are two types of testers, the hand held digital things, and the big old metal box devices with great big resistors inside. Ideally you would find a shop with the latter, as it can really stress test your battery. In my experience, the modern digital hand held testers can not identify a marginally bad battery, only the really bad ones.

Needless to say, if your battery has issues, it will be even more susceptible to the high resistance of poor electrical connections, so make sure all connections in the starting circuit are good. The battery cables, in my experience, can look perfectly fine on the outside, yet the copper wire may be corroded out within the insulation.

I personally don't think your starter is the culprit here, based upon your description. Maybe you should look at some of these cheaper components first?

Good luck,