8.1 overheating/manifold replacement?

[Hey Ray]

I had a mechanic come to the boat to investigate stbd engine not pumping water about 2 months ago, turned out impeller was fine but small piece of cork gasket on strainer was missing causing it to suck air. Easy fix, will always check that first before taking apart water pump! During course of that conversation he was really pushing for replacement of manifolds, which are 5 years old, about 200 hours (engines new Jan '14). I read a bunch on this board and other places about this, and decided to keep on eye on engine temp and riser temp (hand test). Ran engines to operating temp in slip and did hand test, all risers barely warm. Took boat out last weekend, got to cruising speed for about 15-20 mins and port engine pushed just past 170 then alarm sounded. Stbd was just below 170 where it usually is. Shut down port, alarm still on. Shut down stbd and alarm went off. Lifted hatch and touched risers, 3 were pretty hot and 1 just warm. Waited a few minutes and restarted stbd engine, no alarm. Ran back to slip on that engine, all good. Fired up port just to get into slip, both engines pumping water. Gonna get an infrared laser thermometer and take it for another ride and get more accurate readings. Questions are:

How to determine if manifolds are actually done? (I know some recommend doing this as preventative maintenance but that's a tough one to swallow $ wise)

What else can I check to see if there is something else causing the overheating?

Thanks!

 

[superwa]

If you are in salt water you are really risking the engine if you don’t replace them after 5 years or so. Salt is an awful thing

 

[Henry Boyd]

If you are in salt water you are really risking the engine if you don’t replace them after 5 years or so. Salt is an awful thing

Before we sold the 280 this spring I replaced the manifolds for the first time. I know it the first time as we were the second owners and a friend was the original. BTW, they didn’t need to be done, but I didn’t want to argue with potential purchasers.

The point is steel manifolds do only last five or so years. However aluminum manifolds last longer.

 

[LG111]

Before we sold the 280 this spring I replaced the manifolds for the first time. I know it the first time as we were the second owners and a friend was the original. BTW, they didn’t need to be done, but I didn’t want to argue with potential purchasers.

The point is steel manifolds do only last five or so years. However aluminum manifolds last longer.

Aluminum yes in freshwater. Saltwater no more than one year at best!

 

[Henry Boyd]

Aluminum yes in freshwater. Saltwater no more than one year at best!

Take a look at a map. Newburyport is a harbor on the Atlantic. Even ignoring the prior owner’s experience, we owned the boat for last twelve seasons, boating in the ocean. So your one year estimate might be wrong. That said, I didn’t ignore them and we replaced the external raw water rails about every five years. And we Finally replaced them not because of failure, but because selling the boat with new manifolds is easier than arguing the old ones were still ok.

 

[superwa]

I think it’s one of those risks that you have to be comfortable with. To me it’s peace of mind knowing I won’t have to replace the engine because I didn’t.

 

[LG111]

Take a look at a map. Newburyport is a harbor on the Atlantic. Even ignoring the prior owner’s experience, we owned the boat for last twelve seasons, boating in the ocean. So your one year estimate might be wrong. That said, I didn’t ignore them and we replaced the external raw water rails about every five years. And we Finally replaced them not because of failure, but because selling the boat with new manifolds is easier than arguing the old ones were still ok.

You are lucky. I am in saltwater 24/7/365 too and only got one year. Rails failed first in 8 months due to the stainless fitting on the bottom. Then manifolds followed. Secondary was the shluff in the manifolds plugged up one of the dripless cooling lines and killed the dripless shaft seal!!! Terrible design. Merc should have known better!

 

[Hey Ray]

Update - bought a $30 infrared laser thermometer at Harbor Freight and went for a ride with a friend of mine. Got it up to cruising speed and temp gauge slowly climbed again. Lifted the hatch and checked all 4 manifolds and risers/elbows. Manifolds were all around 135 deg, risers/elbows around 100. met with mechanic Sunday morning and gave him that info, he feels manifolds are fine. He thinks impeller may be an issue, with temps going up at higher RPM's. Going to replace that this week and see where we are. Have manifold replacement on the horizon but want to at least get boat up to it's July home in Sac River Delta.

 

[LG111]

Update - bought a $30 infrared laser thermometer at Harbor Freight and went for a ride with a friend of mine. Got it up to cruising speed and temp gauge slowly climbed again. Lifted the hatch and checked all 4 manifolds and risers/elbows. Manifolds were all around 135 deg, risers/elbows around 100. met with mechanic Sunday morning and gave him that info, he feels manifolds are fine. He thinks impeller may be an issue, with temps going up at higher RPM's. Going to replace that this week and see where we are. Have manifold replacement on the horizon but want to at least get boat up to it's July home in Sac River Delta.

FYI, if you set up the BlueTooth vessel view option on your merc, you'll get all the readings in digital English. Like water pressure readings, that indicates a failing impellar.

Also, feel the exhaust water that exits the sides. If it feels like hot tub temp water, you have a bad impellar or blockage that leads to a bad impellar. After a hard run and a minute or two at idle, the water temp should be no more than just slightly warm to cool. Not hot tub temp.

 

[Hey Ray]

Update #2 - Mechanic hooked up computer to read for codes (didn't have it with him first visit to the boat), got no codes for port engine but did get code for overheating transmission on stbd about 2 engine hours ago, about when I got the alarm. Checked filter on the transmission cooler and it was very clogged, cleaned that out and the port transmission cooler filter as well. Ended up changing the port impeller since we had it taken apart anyway, but he thinks its a gauge issue and not overheating. Ended up taking boat from San Rafael (SF Bay) up to Delta (about 50 miles). Once under Carquinez Bridge, got another alarm. Slowed to idling speed and alarm went off, lifted hatch and found a drip from the very short hose that leads from manifold to another hose that leads to stbd transmission cooler. Had a very loose hose clamp so tightened that but drip continued. Had my son increase RPM's then saw water come from small hole in middle of that small hose. Of course I had just taken my Gorilla Tape off my boat to use at home so didn't have anything with me to plug it. Went slow to Pittsburgh (CA) gas dock and filled up, and also borrowed some duct tape from another boater. Wrapped it up and continued to our destination at cruising speed with no issues. Had also checked manifold temps and all were around 135. Gonna replace that hose and makes sure I am prepared if it happens again.