How bad did I break it?

wkearney99 · **Posted:** Wed Jul 18, 2012 6:09 pm

I had a similar issue a few weeks ago. I replaced my thermostat and it solved the problem. I also happened to replace my manifolds and elbows at the same time as they were a bit corroded (after 6 years in salt water). But it was definitely the thermostat that was causing my overheating. My impeller was in perfect shape.

You could do this simple test yourself. Just pull the existing thermostat and boil it in a pot of water with a thermometer. If it doesn't open at it's designated temp then it's bad. I did that with my old one and it didn't budge at 170F or even when it rose to boiling. Thermostats are cheap and pretty to replace yourself.

Shame on that dealer for not actually TESTING that their work solved the problem. Bust their chops on that and get them to get it right before you lose more boating time.

St. Louis Dave · **Posted:** Wed Jul 18, 2012 6:13 pm

I agree. Running it on the hose "up to temp" and putting it in the water are two different things. They'll hear about it for sure.

I hope it's just a t-stat.

NiagaraChillin · **Posted:** Wed Jul 18, 2012 8:51 pm

Holy crud, my boat just did the same thing (just got back 20 min ago) as St Louis....was out on the river, nice easy cruise at 30 mph, on plane, temp at 170 for about 15 minutes. Stopped for a swim, about an hour, started up and took off, again easy going, 30 mph. Next thing I know, temp guage is pegged at 270, and I smell a burning plastic smell coming from the engine bay. Throttled down, took off cover, small amount of smoke poured out. I shut it all down and started checking everything I could. No collapsed hoses, intakes looked clear off debris.

Let it cool for a bit, then started it again, same thing a burnt plastic smell. Shut it down and had it towed in (luckily was within sight of docks.

I'm gonna check the thermostat tomorrow. Hopefully it isn't worse (altho I know with boats it usually is)....ugh. Any tips from the more experienced?

St. Louis Dave · **Posted:** Wed Jul 18, 2012 10:03 pm

Get out your $ for the impeller change and then hang on from there. I'll post as I know more tomorrow to have them check everything at one time for you

bummer!

NiagaraChillin · **Posted:** Thu Jul 19, 2012 7:46 am

Thanks Dave, don't mean to hijack your thread, but since we have similiar problems, a few questions for you or anyone else:

1. If it is the T-Stat, can I use an automotive one? (since it is a Ford 5.0, I assume you can)
2. If it is an impeller (and here is my inexperience with boats showing) where exactly is it? I have the 5.0 with a VP Cobra SX outdrive.
3. The burnt plastic smell has me worried. Is that normal for when an impeller goes bad?

Thanks...

LouC · **Posted:** Fri Jul 20, 2012 12:52 am

One, no you can't use an automotive thermostat, they are rated too high in temp (195 vs 160 is what you need) it may not fit and will probably corrode very fast because its not meant for raw water cooling.
Two the impeller on the later Cobras is on the engine, like a Volvo, it could be in the crank pulley or run off a belt mounted to the lower left side of the engine as you face it
Three the burning plastic smell most likely is the rubber exhaust hoses that connect the exhaust risers with the exhaust pipe that is bolted to the transom (Y pipe as it is known). You should take those off and make sure they are not burned inside, if so replace or else you can have water leaks from the exhaust system. Your exhaust system is water cooled and if the impeller fails not only does the engine overheat but the exhaust system does as well.

Checking this stuff is basic maintenance when you have an inboard/outboard engine. Outboards have impellers too but their exhaust systems are a lot less troublesome. The impeller should be at least inspected each season and replaced every other season.

NiagaraChillin · **Posted:** Fri Jul 20, 2012 7:27 am

Thanks Lou, understood on the auto vs boat parts thing...

Well, parts shopping today, then repairs tonight, then on the water tomorrow....(hopefully I didn't just jinx myself there) wish me luck.

St. Louis Dave · **Posted:** Tue Jul 24, 2012 9:35 pm

The rest of the story...

Barretts to the boat in on Friday morning. Flushed it even more with the hose and got more rocks and sand out of it. Ran it on the hose for a while and then took it into the lake for a sea trial. All was fine and they called me to confirm it was done. After playing golf on Friday (tough life I know) I went and ran the boat hard before we had our guest come out and ski/tube on Saturday. Boat ran great and had no issues with temp. On Saturday with 9 aboard, tubing and skiing, no issues and boat ran great. Even managed to hit bottom again, stir up some more mud/sand, and had no issues.

I'm VERY lucky no other issues have come up and as much as we ran it on Saturday, I'm confident it is fixed.

LouC · **Posted:** Wed Jul 25, 2012 1:09 am

Being a backyard mechanic of 40 years worth I will say that the best diagnostic tool you can have as a boater is an IR temp gun, you can use it to check what temp the engine is
REALLY at (the dash gauges are not all that accurate) and you can note changes so you can spot problems before they get big. As an example, you can take the temp of the area right under the thermostat, that gives you a pretty close read on what the temp gauge should be reading. I found that when my gauge reads 165 or so the most the area right under the thermostat reads is 155 with the gun. While warming up the manifolds read at about 100 or so, after coming off plane they will go up to about 135-125 or so. If I see temps higher than this then I go looking for problems.

I recently had a running hot but not overheating issue where the manifolds were getting much hotter but the engine was not overheating (maybe 10 degrees hotter) the manifolds were going to 160 at idle. I checked the raw water flow and it was OK but while I briefly ran the engine with the impeller off I heard a few puffs of steam escape from the open port on the thermo housing. There must have been some kind of blockage in the thermo housing because after that the manifolds went back down to 100 and the engine went back down to 165 on the gauge. I had replaced the manifolds/risers last year so I knew it wasn't that and the thermostat had worked fine up until the time I could not use the boat for 2 weeks because of vacation.

I'd advise any boater who wants to stay on top of things to get one of those guns and take readings when everything is OK, and then every now and then. Could help you avoid a big problem one day.

ric · **Posted:** Wed Jul 25, 2012 7:12 am

Glad to hear everything is okay!

Maybe it's time to invest in a Garmin with some Bluecharts?

Mark T · **Posted:** Wed Jul 25, 2012 7:38 am

NiagaraChillin wrote:

Thanks Lou, understood on the auto vs boat parts thing...

Well, parts shopping today, then repairs tonight, then on the water tomorrow....(hopefully I didn't just jinx myself there) wish me luck.

Not sure if you have a NAPA auto parts store close by, but the one by me carries marine parts or can have them the next day. I got my thermostat ( Ford 351 ) from them and belts as well. They were not real knowledgeable on the marine thermostat, but when I told him temp range I needed he came up with one that has worked all summer.

NiagaraChillin · **Posted:** Wed Jul 25, 2012 7:46 am

Glad it turned out good for ya Dave, now it will be my turn to report back on my issue (waiting on UPS to drop off parts).

And yes Mark, I do have a NAPA here that carries the marine side stuff. My neighbor actually works there and gives me the first cousin discount :lol:

St. Louis Dave · **Posted:** Wed Jul 25, 2012 9:32 pm

Need rain Ric. Charts didn't help in this case. I was between the red and green...

LouC · **Posted:** Thu Jul 26, 2012 2:09 am

One great thing about salt water boating, there is always enough water, but the depth changes every 6 hrs, high to low. Even at low I can get in and out fine.

650Guy · **Joined:** Tue May 22, 2012 7:15 pm **Posts:** 47

I'm in the impeller (i hope) dog house too. I towed my boat to a new location. During launching it back at home my boat overheated. Didn't catch it until I was backing away from the launch, and it stalled. Don't know why, but I immediately looked at my temp gauge and she was at 240. Let her cool and tried it again, she started and ran fine, but temp started rising again. I shut it down when she rose to about 170.

Wasn't running it out of the water, but had the outdrive tilted up due to the shallow ramp. So I gather I either I sucked some crap up, or the cavitation of the water wasn't allowing enough water in to cool and I'm guessing fried my impeller, and PRAY that is it. Luckily she never broke idle, and the whole episode only lasted 5 minutes. So my hope is not enough time to do real damage. I'll know in about 4 hrs. Couldn't sleep worry'n about her! haa! I have a love affair with my boat.

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How bad did I break it?

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