Here's a stupid question:
What's it mean when the water pressure on the center motor bounces up and down, between 20-30, while the outboard motors stay steady at about 30?

Additionally, the headers on the center motor are turning a bit blue. Is this an excessive heat problem that needs to be addressed.

NOTE: Center XR was replaced and there were questions about how many "plugs" went into the water pick-ups.

I just keep thinking how hard it is to feed 2 motors, 3 must be a biotch! Sorry I couldn't help.

i wont own a boat with out pressure gages but they are very glitchy

where is the pressure sending tube attached ?? to the Block ??? (should be) of the center engine they are glitchy but should read consistent you get sand or debris in them an they don't work well

as far as the pipes turning blue HOUSTON WE HAVE A PROBLEM
that should NOT be happening so you may not have enough water or something else

a new impeller wouldn't hurt just to make sure that you got enough flow going on

Could the outside drives be starving the center of water? "Cavitation"? Are you turning in or out?

I am no mechanic, but just a thought

Sounds to me like the center drive is not getting enough "clean" water. Without seeing the boat, picture or in person it is hard to tell. Do the XR's have low water pick ups? If so, could it be that the drive might be a little too high on the transom and be getting a gulp of air every once in a while. If this isn't the case and you don't have anything mounted on the transom right in front of the drive that would "dig" a hole in the water in front of this drive, start looking hose that supplies the water to the suction side of the raw water pump. There is a hose that is in the gimble assembly, then the one that attaches to the top of the inner trasom plate that runs to either a stainer or the suction side of the raw water pump. Make sure there are no pin holes that air can get in and cause the pressure to flucuate. Make sure the hoses are running smooth and as straight as possible. Seems like the fitting on the inner transom plate might even be plastic, if so check for cracks. If the impeller can't get enough water, it will cause a spiking water pressure situation like you have. I hope this helps. Oh and BTW, if you don't know the answer to the question, it isn't a stupid question!

Robert

Tonto, that's what I was getting at, but you said it much better

Check the impeller, our port engine started doing the same thing last time out. Temperature never rose but we kept an eye on the pressure the whole day. I figured it might have a blockage going to the gage. Last weekend I had to take the boat off the trailer to move another boat. Launched the boat and just put it in a slip, not enough running time to heat anything up. When we went to pull the boat out I had to idle at the ramp area for a while, noticed the pressure did not move at all and next thing I know the temp gage was moving up quick. Did not over heat anything, just shut it down until tomorrow night when I get to change the impeller.

Just another angle to look at

Bingo...
Thanks Robert for typing what I tought although in much better terms... saved me some time!!!
I'll get you a pop in Key West then!

Thanks for the input. Robert, I forward your entire reply to my dealer. BTW-these are BRAND NEW motors...brand new everything, in fact
t500hps: it does seem like it'd be a bee-atch to feed three motors, but these 525s are very efficient and with 3 of them doing the work, none of them has to work that hard. The big benefit, though is that they run on 87 octane and I don't have to use $100 worth of gas to find 93.

Install a sea-strainer on just the center engine. It should take care of an otherwise border-line water intake supply.