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crqflier

Symptoms indicating new manifold/risers needed? Or?

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Our boat - 2004 220ssi with VP 5.7 Gi, SX outdrive. ~160 hours total time since new. 1 time in salt water 3 years ago (flushed afterwards). The rest all fresh water.

I've read several dozen posts here and on other sites, so my apologies for another thread on the topic.

Put the boat in the water this weekend for the first time this year and "thought" everything was good to go. Let it idle in the slip for 15 minutes - solid temp of ~170. Smooth throttle. Rev'd in neutral to 3000 rpm for a couple minutes. Steady temp. After taxiing out of the marina and slow speed area (5-7 minutes underway) and then going WOT to get up to cruise (25 mph), we settled in. About 5 minutes later, temps rise to ~200 -210. I shut the engine down immediately and call the lake patrol for a tow back to the marina. At that moment, water pump housing was cold, no leaks, riser/elbows warm, but could easily hold hands on them for as long as I cared to.

Back at the marina, I start to trouble shoot.

First thing is a new impeller. Old one going on 3rd season. Not "bad", no missing fins, some minor cracking at the base of a few fins. After install, idle for 10 minutes - solid temp (170), cold pump housing, cold hose to thermo housing, risers are easy to touch. Rev to 3000 rpm and temp begins to rise - shut down.

Second - ensure temp sensor connections are firm (I believe that's what they are) on back of both risers, both sides of the block at the drains, and at the thermo housing. Go through same test routine. Same results.

I notice that the port riser cools a bit under high rpm (more water flushing through?) and that it is definitely cooler to the touch than the starboard riser - though both are easily touchable (for as long as I care to touch) as I see the temp rise. Are the two risers typically the same temp? Seems like they should be. I don't have an IR thermometer, but there was definitely a difference.

2 questions:

  • Does this sound like clogged manifolds/risers (or perhaps just the starboard)?
  • How does the temp gauge work? Are all 5 of those sensors I described actually temp sensors? Or is the temp sensor somewhere else? Do they feed a common circuit that then takes the "highest" reading and that's what shows on the temp gauge? Or?

I don't think it's the thermo - the engine idles no problem for extended periods and maintains 170-175 degrees - though I could easily replace it (which I didn't do yet). Clogged PS cooler maybe - read a post about that, but symptoms aren't an exact match?

Our boat is 2.5 hours away, so I'm not really able to do any more trouble shooting. But from what I've read, 10 years is a fairly predictable replacement range for fresh water operation. I'm considering purchasing manifolds/risers and just "throwing parts at the problem" DIY - seems doable except for potentially rusted mounting bolts. The boat is up a 8000 foot mountain, so pulling it down to a VP mechanic and back up isn't trivial (or free), which adds to my thought of just replacing the risers/manifolds and seeing if the problem is solved.

What would you do? Appreciate any thoughts.

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I think I'd change the thermostat before I'd change the manifolds & risers. A lot cheaper and a lot easier. If that doesn't fix it then maybe the manifolds & risers. Also, make sure you're not sucking air somewhere. Be sure the cap on the flush hose is secure.

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Thanks Pat. I should have replaced the thermo while I was up there yesterday - shop didn't have one - just to rule it out. Air entering the system seems like another place to look. I'm fairly sure the garden hose cap is firmly on, but I'll definitely check. I also read that I can test for other air introduction by flowing water through the garden hose connection and not turning on the engine - only water egress should be at the water intake on the outdrive. So I'll try that.

Sounds like the right approach is some more testing and less expensive alternatives - just not easy since it's a minimum 5 hour round trip. I was just "hoping" to be equipped with all possible parts needs for when I head up for my "repair trip". Once I pull the boat back out, I wouldn't want to put it back in until the issue is resolved. Since I can't leave it up there (securely) unless it's in our slip, if the problem isn't resolved I'd need to tow down the mountain and find another storage spot. The mechanic at our marina is not a VP guy and suggested I take it somewhere with a VP guy (if I don't DIY).

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Manifolds and risers last a LONG time in fresh water and even salt water if properly flushed out. Change your thermostat, you should be running 160 if RWC. My risers are never the same temp. The starboard side always runs much hotter. I only have hoses going through the manifolds, so my risers don't get as much cooling water as yours probably do if they are that cool. The temp sensor (at least on older carbed boats) is usually on, or near, the thermostat housing. Typically the engine should run 160 (or lower if at idle), but the manifolds and risers will be much cooler. 160-175 will burn you, but the manifolds and risers should never burn you. Clogged manifolds and risers would be very hot and untouchable. They also don't dictate engine temp (they dictate exhaust temp which shouldn't be scolding hot either), the thermostat does.

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Thanks Drew. I guess I was thrown off about the thermo by the fact that I could idle (pretty much indefinitely) without temps going crazy. Maybe that's a partially open thermo - enough to cool at idle but not enough at throttle. So the single sensor for temp is at the thermo housing - not the sensors on the risers or down at the block drain plugs? Makes sense, just didn't understand the other sensors. T-stat housing is above the water line, so I should be able to do this with boat in the water - guessing.

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Thanks Drew. I guess I was thrown off about the thermo by the fact that I could idle (pretty much indefinitely) without temps going crazy. Maybe that's a partially open thermo - enough to cool at idle but not enough at throttle. So the single sensor for temp is at the thermo housing - not the sensors on the risers or down at the block drain plugs? Makes sense, just didn't understand the other sensors. T-stat housing is above the water line, so I should be able to do this with boat in the water - guessing.

The lower block wall sensors are knock sensors, and the ones in the exhaust will set an alarm but have nothing to do with coolant temperature indication. W

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Thanks Wingnut.

Seems like the thermo is the next step unless someone else has some thoughts on going after the riser/manifolds. Sure would be great if it's a partially stuck/blocked thermo or a loose flush cap. If not, I'll pull the boat out and check for other air leaks.

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ive owned and been in boats that were 15-20 years old and original manifolds look new.. my guess is thermostat. Maybe the impeller is good, but your impeller housing and shaft are smoked?

To be quite honest what your describing seems like a classic thermo issue as in at idle its fine then once underway it gets hot. If you want take out the thermo boil water and see if it pops open. But you can get a thermo kit for less than 20 bucks, its just as easy to rip out the old and replace with new while your at it.

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If you have the vovlo fresh water make sure the cap is tight, also have you run aground at all sand can get clogged in the oil coolers.

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