MC-1 Back Together, Temp 175 Fahrenheit?

[Tacoma_Dave]

First things first...Let me take a moment and thank you all for the advice and direction. I certainly couldn't have done it without you all. So, the impeller has been replaced, the upper/lower housings back together. Shifting is working just fine, so I slap the muffs on her and fired her up. Of course the engine is a 470 and I've read threads and warnings about overheating, so I'm a bit wary of that. After about 7-8 minutes at idle, the temp gauge was reading at about 175 degrees and remained stable. I'm not sure whether the gauge is accurate though. The engine, once warmed up, runs fine. I guess my question is...If 175 degrees is accurate, would it be OK to take it out on the Sound?

 

[nola mike]

No. You have a 160' stat, if it's running that hot at idle something's wrong. But your gauge for sure might be off. Double check with an IR gun or a thermometer radiator cap or something.

 

[Eric 3.7LX Alpha 1]

Man now I really like you... Lol didn't know you were working on a 470.

After 7 or 8 minutes already running warm sounds like a sticking thermostat or maybe the wrong temp one, or off gauge like Mike mentioned.
Mine runs at 160 all day long. I also have one of those Mr gasket thermocaps, and it works nice built mechanical temp gauge into the rad cap for when I have the engine cover open and to confirm the dash gauge. I have the 4" diameter heat exchanger, the older models had a 3". But even a 3" should not get that warm that quick on muffs at idle.

What's the story with this? Is it new to you boat/engine or have had it for a while?

 

[Tacoma_Dave]

Man now I really like you... Lol didn't know you were working on a 470.

After 7 or 8 minutes already running warm sounds like a sticking thermostat or maybe the wrong temp one, or off gauge like Mike mentioned.
Mine runs at 160 all day long. I also have one of those Mr gasket thermocaps, and it works nice built mechanical temp gauge into the rad cap for when I have the engine cover open and to confirm the dash gauge. I have the 4" diameter heat exchanger, the older models had a 3". But even a 3" should not get that warm that quick on muffs at idle.

What's the story with this? Is it new to you boat/engine or have had it for a while?

Hey Eric, yes, this is new to me. I followed Mike's advice and already ordered a Mr. Gasket thermo cap for pickup tomorrow. I purchased a 4" exchanger on ebay, but someone told me, after I purchased it of course, that I can't install it in my rig because It'll foul things up. Never thought of stuff like that, but then again, I've only ever worked on cars and motorcycles. Done my fair share of engine rebuilds/swap...but boats are a different beast to me. Changing out a stat shouldn't be much different than on a car though I would imagine, yes? 1978 21' Fiberform Cuddy w/ a 470

 

[nola mike]

Hey Eric, yes, this is new to me. I followed Mike's advice and already ordered a Mr. Gasket thermo cap for pickup tomorrow. I purchased a 4" exchanger on ebay, but someone told me, after I purchased it of course, that I can't install it in my rig because It'll foul things up. Never thought of stuff like that, but then again, I've only ever worked on cars and motorcycles. Done my fair share of engine rebuilds/swap...but boats are a different beast to me. Changing out a stat shouldn't be much different than on a car though I would imagine, yes?

Yeah, tstat isn't anything special. Not sure why you can't use the 4" HX. Do the plumbing fittings look the same/in the same place?

 

[Tacoma_Dave]

Yeah, tstat isn't anything special. Not sure why you can't use the 4" HX. Do the plumbing fittings look the same/in the same place?

Exactly the same...Perhaps bad advice then? I mean honestly, never heard of anything like that, ya know?

 

[nola mike]

Exactly the same...Perhaps bad advice then? I mean honestly, never heard of anything like that, ya know?

I think @Scott Danforth said something along those lines (don't remember if it was in response to your thread or another)? If it physically fits, and the internal flow is the same, IDK. I don't have a manual for the old 470's to compare the cooling flow to the newer ones.

 

[Eric 3.7LX Alpha 1]

Here is the cooling flow diagram from Manual 3 which covers All engines & drives 1978 -1984



And here is from manual #8 which covers the newer models with the 4" exchanger.

 

[Eric 3.7LX Alpha 1]

The older manual 3 goes into cleaning the heat exchanger, says it should be done every two years.


and also mentions the 4" exchanger on the following page. You should be good as far as connections go, you may have to fabricate two new brackets to accommodate the larger diameter if the 4" doesn't come with them. When you see MIE, that's an inboard without an outdrive, we have MCM version.

 

[Tacoma_Dave]

The older manual 3 goes into cleaning the heat exchanger, says it should be done every two years.
View attachment 349526

and also mentions the 4" exchanger on the following page. You should be good as far as connections go, you may have to fabricate two new brackets to accommodate the larger diameter if the 4" doesn't come with them. When you see MIE, that's an inboard without an outdrive, we have MCM version.

View attachment 349527

Wow...This is awesome! Thanks Eric!

 

[nola mike]

Wow...This is awesome! Thanks Eric!

I bet he has the whole manual.

 

[Eric 3.7LX Alpha 1]

Were you missing any fins on the old impeller?

 

[Eric 3.7LX Alpha 1]

I bet he has the whole manual.

I was able to get a few back when we could.

 

[Tacoma_Dave]

Were you missing any fins on the old impeller?

They were broken and 1 piece was "missing" but I believe it came off when I removed the housing since I found it right below in the metal gasket flange. They were broken and in bad shape, but I don't believe any pieces made it into the system. Here's the pics...

 

[Scott Danforth]

The 4" HX was designed to replace the smaller HX as a field replacement

That impeller is toast

 

[Lou C]

Some muffs don't fit well enough to give the engine enough water, the best one I found were the Merc/Quicksilver round ones with the clamp to hold them on. The rubber is softer than the Tempo rectangular dual feed ones and they seal better. I had trouble with the Tempo ones, I think they made the rubber stiffer and they don't seal as well. Try backing it in to the water that is a better test of an impeller anyway.

 

[Tacoma_Dave]

Some muffs don't fit well enough to give the engine enough water, the best one I found were the Merc/Quicksilver round ones with the clamp to hold them on. The rubber is softer than the Tempo rectangular dual feed ones and they seal better. I had trouble with the Tempo ones, I think they made the rubber stiffer and they don't seal as well. Try backing it in to the water that is a better test of an impeller anyway.

That may be worth checking out. The muffs that came w/ the boat are rather stiff and they do leak an awful lot when the water is turned on and engine running.

 

[Lou C]

That may be worth checking out. The muffs that came w/ the boat are rather stiff and they do leak an awful lot when the water is turned on and engine running.

That may be your problem. These are the best!

 

[Lou C]

Much better mine will run a 140* all day if I want.

 

[Tacoma_Dave]

Well, I think we may have an issue. I placed the thermo cap on and started the engine. Now I know I shouldn't run it w/ the prop going, but I noticed no water coming out from anywhere on the sterndrive other than the muffs. I tried it in neutral and forward and didn't notice anything. My wife took a vid while it was engaged and nothing...Like I said, either in neutral or forward. When I shut it off at 175 degrees, steam started coming out from 2 holes in the sterndrive...so my question is...is water supposed to be coming from them when running? See the pics of what I'm talking about. Thanks again...

Steam...