1997 Tournament ski 350 - riser temp range? whats too hot?

Hi all - have a 1997 Tournament ski 350 (SN ok147313) - boat was running hot stbd side and melted exhaust - replaced hose and did a full service - water pump - this is a thru hull, with external flappers that open easily.. on hose @ idle risers are perfectly cool after 5-10 minutes. Soon as I start heading out/driving under load - they get hot - and the temps vary a bit depending on speed / load etc.. but much hotter than im comfortable with-

Whats the exhaust tube for that runs from the cross over on the intake manifold to the stbd riser port?

seems like theres a ton of water flow - hoses are pouring water out that feed to the manifolds. I tested with a 2nd pair of manis/risers that came form a same engine boat with no heat issues and same symptoms..

This is the 1 hose t-stat style with 1 hose per manifold... i know they run hotter and I have spare laying round - might test with a 4 hose t-stat housing.

Block temps never went higher than 175 - im considering putting in temp senders on the risers with an alarm - i guess 200 is just waaay too hot? risers should be around 140-160 max under cruise?

This is a 18ft cuddy ski boat-

Sample pic




SN of my motor:

I noticed you replaced the raw water pump... Was the old impeller intact when you removed it?? If not, you need to find the pieces. They like to camp out in the t'stat housing and plug up the ports that dump water into the elbows. however, if you tried another set on elbows with same overheat, I vote for pieces in the T'stat housing

The manual for that engine specifies something like 40 gal per min raw water flow at cruise.

BTW... they are called "elbows", not risers... If you can't keep your hand on them while running they are too hot... same for manifolds ( except for the very short link from the exhaust port to the manifolds.)

hi sandkicker - thanks.. old impeller was intact, i had the tstat housing off 3 times - i will try the water test today as i went out to catalina yesterday with the wife.

I have been able to hold my hands on the "elbows" on other vessels and usually consider it a proven "test" method that water is moving correctly - these are REALLY hot.. enough to warrant concern despite them not even being run hard for more than 2 minutes..

I found this on tht -

"I was googling around and found a post from a guy who was having the same issues with his MerCruiser. He wrote MeCruiser customer service and they replied with the following:

"The water coming out of the engine block exits only on the starboard side of the engine. Therefore the starboard exhaust manifolds and exhaust elbows will be warmer than the port exhaust manifolds and exhaust elbows. This is normal for your engine. If you have a 160 degree thermostat installed the temperature of the exhaust manifold on the starboard side of the engine can get up to 176 degrees under normal operation after the engine has reached 160 degrees. The temperature of the exhaust manifolds and exhaust elbows can also vary depending on the temperature of the water, the ambient temperature and the humidity."

Just wanted to share incase others come across my post. I will continue checking for blockages, but the difference in temperature that I am seeing thus far makes me think this is the culprit."

Well I found a ton of old impeller parts in the transmission cooler - all is well now thanks!