Hope somebody can offer some insight. My Vmax starts great cold such as unloading (pops off right away), but as soon as I run the boat for awhile, make a few stops and fish, the engine gets harder and harder to turn over as the day goes on. When it does turn over it will quit occasionally, like it's really struggling to keep going (sounds like it's idling really slow). I've checked the idling speed and it's at the recommended RPMS per yamaha manual. Should I crank the idling speed up? Any other ideas? Thanks

Maybe starter drag.

sounds like you're losing compression at warm temperature. I would think the things that could cause this are the need for a valve clearance adjustment, bad thermostat or blocked water passage, or possibly head gasket.

I really don't know much about motors, but am slowly learning. so take this for what its worth, which could be nothing.

Johnny

Is your motor an EFI or a carb model and what is you model number?

1998 V-Max 200 was 0-66 EFI... as I recall. (2 stroke , of course)

Better have that checked out.
A bad 02 sensor can cause bad things.

I assume your water pump is pumping and you are not overheating..... right?

PJM, Sorry for the delayed response. It is an EFI ox66.

T-Mac, as a matter of fact it does overheat when idling in warm water (like when waiting to load up, started doing this last year). Water pump replaced this spring, but just noticed the overheating again this last weekend. I just read recently on one of the older threads somewhere about poppet valves being a problem with the Vmax's? Thanks for the replies from all of you guys, sounds like I need to get it in to the shop again.

Sounds like you should replace your power wires going to the starter.. heat + more reistance in the wires = harder starting. check your ground and connections make sure they look good, no corrosion and tight.

Johnny

Being that it is an XO 66 EFI the oxygen sensor could be bad or dirty. Also that motor has three fuel pumps and if they are bad that could causing some smoking and bad idling If the diaphragm is bad you could be leaking fueling the system causing a it Idle rough.

Have you ever changed the 3 fuel pumps?

I had two of the fuel pumps replaced three years ago and it ran fine until late last year. I brought this to the mechanics attention last year that it was a hard start when warm. He stated he checked the entire fuel system and everything looked good, he didn't do anything but add some ringfree fuel additive.
I'm taking it in early next week, thanks again for all of the replies, wish I was better with motors. I'm just wondering how they will be able to detect the problem when it only happens after it warms up and has been in the water for quite some time, I suppose it will be a hit and miss thing. Thanks again you guys, at the very least I can mention your different takes on the possible problem and maybe one of them will be something the mechanic (a different mechanic) didn't think of.

Those motors had a problem with the water pick up tube cracking and not allowing all of the water flow to the block causing a overheat problem at idle. Have your mechanic pull the lower unit and look up into the tube with a bore scope. He will be able to see if it is cracked. If it is the powerhead will have to be removed to replace. You might spend more money on diagnostics than replacing the tube. I have seen it a dozen times over the last two years. Maybe this could save you some diagnostic time.