Coachman RV won't start after it's warm

I have a 1987 Coachman RV. It starts ok, but when I stop it won’t start again for hours. It makes a ummm noise instead of a clicking noise. It seems that something must be affected by the engine when warm. All I know is when the engine is cold it starts but when warm it won’t. And sometimes when starting a loud metal sound like something metal is hitting something. Any help would be appreciated. The starter was replaced by a friend, maybe not sitting right?
Thanks so much

Sounds like a few possibilities- the starter motor is improperly shimmed, the starter motor bendix is dry or gummed up and not extending all the way, the power to the starter motor is low due to bad connections or the starter motor itself (or solenoid which is part of the assembly I believe) is going bad. The failure when warm may be some of the above but also due to having lost or left out the heat shield that helps protect the starter from heat soak when starter was replaced at some point.

Still could be a bad starter.

Possible causes…

It sounds like the starter may not be engaging the flywheel. When you try to start the RV, the starter’s wheel is extended a couple inches until it reaches the flywheel, then it starts spinning/turning the engine.

If not engaging it could be.

. When hot the starter is weak.
. Some starters require shims, and maybe too many shims were in. When cold the metal is contracted, so the starter will engage the flywheel. But when hot the metal has expanded and now the flywheel is too far away to expand.