1997 Tournament ski 350 - risers running really hot..

[CamaroMan]

Hi all- got a real tricky one here.. cant figure out why this thing is running so hot. Traded this and almost got it free- boat interior is in excellent shape.

I recently did a full service - rotor, cap, plugs, oil, impeller (housing and everything else was in excellent shape) -

Boat starts and runs fine - max engine temp was 175 degrees - but the riser tops get really hot, too much for my liking-

swapped manis and risers for a pair from a boat that ran fine - plumbed them in and still - water gushes out of hoses. I removed the tstat today and swapped in a new 140 just for testing - no change.. When i get off power the risers cool a bit - im used to them not being this hot..

Still - think is running way too hot. Its a single hose to bottom center of manifold design -

Any ideas? This is a direct drive, water pickup thru the hull - exhaust flappers (external) are free and open easily..

Really stumped - any ideas?

 

[CamaroMan]

Oh - wanted to add, there seems to be a hot exhaust pipe running from intake manifold to the starboard riser - what does this do? Can i plug the holes and remove it?

Dont have sn on me but apart from the exhaust pipe the plumbing is like this one:

Tomorrow im gonna check timing and make sure its advancing, might swap the circ pump (could a failing circ pump cause heating issues on the risers?), might send borescope down exhausts - and test 15 water test on pump output -

Im wondering if a failing fuel pump could cause a lean/hot condition on the exhaust gases? Pump is whining so probably disassemble that and check for issues :-