I give up!

I have a really nice 1990 Mainship 36 Express that I am constantly having to keep my cooling system at perfectly maintained levels during the summer just to keep both engine's temperatures at bay. The problem? Nothing with the boat I believe. Ok, well yeah one engine is more touchy than the other but both HE's are completely clean, both impellers perfect, both U-coolers flow freely, new risers, etc.. Every summer I have the same deal.. Always wants to break out past 175 unless everything is perfectly perfect. The one engine that isn't touchy, even if that behaves, it still has to play catch up after coming down off plane to get rid of that heat. Why?

I'll tell you why! The water temp in freakin Tampa Bay is 92 degrees right now!!! That's right, 92! The other mitigating factor is that I'm running a FULL closed cooling system. The heat exchanger has to take on the load of cooling the exhaust manifolds as well as the block.. Plus I dock in Apollo Beach, right next to the power plant where it dumps hot water into the bay on top of the hot bay water leading into the hot gulf (close to 90 degrees in the Gulf!!)..

The only solution I see at this point is re plumb it as a half system and install an inboard flush kit. Sure, seawater will flow through the manifolds now but I'll flush it out at the end of the day so it's a good trade off.

The half system is a lot more efficient at the expense of wear and tear on manifolds but the HE will only have the load of cooling the block and from what I've read, most systems down here are half systems for this very reason. I wouldn't even be having this one way discussion if I lived on the Atlantic side of Florida.. It'd be fine. It'd be fine with some blockage even..

...I will be shocked if this doesn't fix my summer problem once and for all..

Or, I could wait until September when the temperature drops 5 degrees.. Literally, that's all it takes.. When the incoming water is this hot, I just have no margin whatsoever....

Thoughts? Comments?

-Randy

Oh yea, I forgot, they are twin 7.4 Crusaders.

I don't think so. I mean, I put many hundreds of hours on a twin 454 in 88 degree water, and when there was an overheat issue, it had a mechanical cause. You say the impellers are perfect, OK, but what about the pump cam and rear cover. Are they perfect? Are the oil coolers original, never pulled apart? You may still have some high risk suspects.

Time to relocate!

Jeff (boating on the cool Chesapeake!)

diver_dave said:

I don't think so. I mean, I put many hundreds of hours on a twin 454 in 88 degree water, and when there was an overheat issue, it had a mechanical cause. You say the impellers are perfect, OK, but what about the pump cam and rear cover. Are they perfect? Are the oil coolers original, never pulled apart? You may still have some high risk suspects.

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Twin 454 what, pushing what?.. Crusader or Mercruiser?*Speedboat or a 7 ton cruiser? *How was your cooling system set up? Full or Half? Makes a big difference.* From what I've read, if it's a Mercruiser there is a high probability they came set up as a half and Crusaders are mostly full systems.* Benefit, you only need to change risers, downside: the engines are more temperature sensitive and you need to be a lot more on top of the cooling system.* Regarding the U-Cooler, yeah, both changed regularly.. The salilnity of the Gulf is very high, you run through U Coolers and HE's quicker down here than up north..*I dissasembled the raw water pump and the cover is nice and smooth.. I got tons of water flow out the exhaust on both engines..* I'm not saying that they are overheating, but they just can't hold tight when the water is this warm.* It's like I always gotta be watching..* Believe me, 88 degrees is warm yes, but I'm right on the fringe this time of year, EVERY year and 5 degrees would put me back steady and holding under 175.* I have to stay so on top of this in July & August, and then*I don't have to worry about squat after Labor Day..

I think the incoming water is just too damn hot for a full system here.*

Jeff:* Yeah I lived up in Virginia Beach for 9 years, it's n ice, it's like Florida-Lite.

Here is a great article I found:* http://www.perfprotech.com/store/articles/fresh-water-cooling.aspx* Half systems vs Full systems

..."Yeah I lived up in Virginia Beach for 9 years, it's n ice, it's like Florida-Lite. "

It's Florida without the concrete-wilting humdity, squadrons of bugs, hungry alligators, etc.

Jeff

fastjeff said:

..."Yeah I lived up in Virginia Beach for 9 years, it's n ice, it's like Florida-Lite. "

It's Florida without the concrete-wilting humdity, squadrons of bugs, hungry alligators, etc.

Jeff

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True but there are so many more hot women down here all year round...Not to mention the fishing is outstanding..

Makes it all worth it.


...back to boat repair. lol...

If it is a merc system, it is more likely to be set up as a full system unless it was specifically ordered otherwise; crusaders are done the same way.

If you want to go thru the swap, by all means do so. There's nothing that will get hurt running your engines at 180 vs 175, even up to 190 as long as the water is making it into the exhaust. Like DD suggests, I'd suspect there is a reason.

If you have never done a major overhaul on the pumps, I'd bet the cams are well past their optimal wear point. Regarding their efficiency, the only way to determine that is to measure their outputs...looking, especially at the exit of the exhaust just doesn't cut it.

makomark said:

If it is a merc system, it is more likely to be set up as a full system unless it was specifically ordered otherwise; crusaders are done the same way.

If you want to go thru the swap, by all means do so. There's nothing that will get hurt running your engines at 180 vs 175, even up to 190 as long as the water is making it into the exhaust. Like DD suggests, I'd suspect there is a reason.

If you have never done a major overhaul on the pumps, I'd bet the cams are well past their optimal wear point. Regarding their efficiency, the only way to determine that is to measure their outputs...looking, especially at the exit of the exhaust just doesn't cut it.

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Understood.. One more thing to check out when I take it all apart this weekend. FWIW the water pumps (not the seawater pumps) on the engines are probably original (22 y.o.).. That's pretty much the only thing at this point that isn't new.

EBasicPower has them for $109, nothing bad can come from replacing them...

You might get an IR gun to read temps. They are available on the internet for around $50. The gauge only reads one spot in the system and makes toubleshooting hard. With the gun you can verify that your gage is correct, and then read the temp levels before and after the exhaust manifolds and before and after the heat exchanger, etc. Also you can compare all readings between engines and find the weak links.

With a closed system an autoparts store "fresh" water pump should be fine. You don't need to pay extra to get the non corrosive marine impeller.

Finally, make sure you cannot turn the water pump by hand. A loose belt will allow the engine to work well at low rpms but cause flow reduction just when you need it. And if you change a belt, ONLY get a genuine Crusader belt. I found out the hard way that "equivelent" belts can bottom out on the pulley as they wear in and start slipping. And if a belt is not running on the sides, tightening it up only last about an hour.

CaboJohn

For the record, my rig is 4 to 5 tons, full cooling, old crusaders. Like MM says, if you run less than 190 at the engine output and don't boil coolant in the exhaust manifolds, i wouldn't worry. If, on the other hand, you are running 50% antifreeze, stop that nonsense now. Drain out all the 32 quarts of prestone, etc, refill with clean water and put in the Detroit Diesel additive, I think they call it Power cool 3000. It has no antifreeze, and it conducts heat much better than the glycols.

2X DD's thought on minimizing the coolant's ethylene Gylcol content. make sure the coolant additive contains a water pump lubricant; if not, a couple more bucks for a pair of cans is prudent.

On changing the circulating pumps, I'd go with a marine replacement for two reasons: 1) they come with a bi-directional cast impeller whcih is much better than the stamped steel auto versions, & 2) they are assembled with higher quality parts to ensure long service life...a big driver in what the marine units cost more.

Have you tried changing the coolant? I have a similar problem up on the Chesapeake and this helped. And cool?? In mid bay I normally see 86-90+degree water!

rmm said:

Have you tried changing the coolant? I have a similar problem up on the Chesapeake and this helped. And cool?? In mid bay I normally see 86-90+degree water!

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Hello everyone, (condensed responses from all feedback)

well I replaced the engine circulating pump (I say it like that so we all don't confuse it w/ the raw water pump). I bought the marine one from EBasic Power. The one I pulled off the engine looked like it might have been the original from 1990. I can't turn the raw water pump by hand. I've fully flushed the cooling systems earlier in the year. I put it all back together, fired it up and took it out. The bay water was 93 degrees and 95 degrees by the power plant. I brought it up on plane and the engine in question has voluminous water flow out the exhaust and it held at 175, high by my standards, warmer than the other one (170), but it held. The thermostat is brand new. 175 is not overheating, it's not really even out of normal operating range I guess. I just want them to both be the same, and they will be after labor day anyway. For peace of mind and a lot more margin of cooling power, I'll probably do the half system anyway since the inboard flush kit is so great.

My marine mechanic says I'm chasing a ghost and this is merely a bay water temperature issue since I only run into this in July / August. My other boater friend says my issue is not an issue and there's nothing wrong.

I'm just OCD about the engines being under 175 because of some paranoia over some previous oversights that cost me huge.

Boat runs fine, sounds great. When I come off plane the temps go back down normally and there's nothing unusual about any steam / etc.. Oil pressures are nice and high.. blah blah blah..

Thots?

I'll sell you a 20 dollar roll of black tape that you can use to cover the temp gages during those two hot months.

Your buddy Jeff

fastjeff said:

I'll sell you a 20 dollar roll of black tape that you can use to cover the temp gages during those two hot months.

Your buddy Jeff

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Ha ! Funny.. So, other than me checking the timing and it possibly being off a few degrees, and with no apparent cooling blockage, is the general consensus that this is a non issue / bay water temp issue? I can't see anyone boating anywhere where the water could be any warmer...