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closed cooling question

zackie77, My thoughts are that the boat originally had a 3.7l (470). It may have blown up and the guy found another engine but was an earlier version. I think a 1982 470 should have an iron log style exaust manifold. He may have taken parts from the later style engine and swapped parts. They are all the same, horsepower was increased or decreased by either four barrel or two barrel carb. Internals should be almost identical except for maybe flattop pistons vs. notched. Anyway, what I am trying to say is they are all 470 blocks just alot of crazy names from I think 1974 til 1989. Merc. put these engines in early 90's boat fairly often. Maybe do a compression test on the engine before you spend any money. How many hours are on the engine? Does it have an hour meter? best of luck, Tom
 
engine has aluminum manifolds and 4" heat exchanger, I think your right what I think may be going on here I noticed a new valve cover gasket, may have put a 485 valve cover on it, the boat shop guy says it"s the original motor, he checked the serial# says yup it"s original.
 
just to update, took boat out today ran fine, 5000 rpms 45 mph for a short burst, is 5000 rpm"s to high? no coolant or oil leaks, temp never went past 150 deg. so far i"m happy with it, heard alot of horror stories so I am very wary and watch it very closely, I do app. all the advise.
 
Great...I told you it has a great power to weight ratio. It's an old engine so keep the RPM level below 4800 and enjoy her while she can still swim. Check the oil and coolant before you take her out and when you return. The purpose is to catch any seal failures asap. Keep an eye on the gauges esp. the voltmeter to detect a regulator failure...it will happen. I use an IR thermal temp. gun to check exterior temps. on the engine and manifolds. If you get used to the numbers you see when it is running correct then you'll spot irregular temps. when they occur.
 
looked at the serial# on the block, doesn"t match the valve cover, but it does match the # on the the carb. cover, looks like it"s a 87-89 3.7 165hp. somebody changed the valve cover and gasket
 
zackie77, I think 5000 rpm's is way too high for this engine being that it is 87-89 470. On my 1988 3.7lx 180 hp four barrel, the valve cover reads: (wot-4600-4800rpms). You have the two barrel version so I think it should be running wot at around 4200-4400rpms. You may be able to step up one pitch on your prop but you have to make sure that it can still reach the manufacturers wot. It sounds like you have a good engine by what you have stated. Like I said before, these little motors seem to be happy running around 3600-3800 all day long. When you push it you really have to be looking at all the gauges. (coolant temp.,oil pressure etc.) Just my opinion, but if I were you I would stay with the two barrel being that it is a little easier to locate a carb. The four barrel quadrajet is becoming harder to come by these days. I bought three used carbs over the course of a year or two just to avoid future problems with NLA parts issues. It sounds like your boat is nice and light with respect to power to weight ratios. In other words, I would not change a thing! lol That's a pretty darn good speed if indeed you are using gps in doing so. You will find while running at around 3600-3800 rpm's, you will burn alot less fuel and the motor will run cooler. These engines are great on fuel! Last time out I think I burned about $68.00 and that was an eight hour day. You stated that your engine was running at around 150 degrees. Something doesn't add up. Either your temp. sending unit, gauge, maybe wrong thermostat. (something isn't right!) You should be up in the 180-190 degree range especially after a hard run. I would do as guyjg suggested and check everything out before your next trip just to be safe. Make sure you change your oil and fuel filters regularly. And what ever you do: "don't overheat that engine!"! It's just too much work and money down the drain which can all be avoided by a little effort on your part. Hey, anything man made will eventually fail but if you keep what I said about rpm's to heart you stand a chance of having a good little runner for quite a few years. jmho best of luck.Tom P.S. You have to run that engine with the OEM thermostat in place! It cannot be removed! Maybe check to see if it is stuck open or maybe someone removed it. I hope that is not the case but you need to be sure. If you do need a thermostat, make sure you get the right one. I think my thermostat opens at 165 degrees. Just something to think about, that's all.
 
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1973 Browning Marine said:
zackie77, I think 5000 rpm's is way too high for this engine being that it is 87-89 470. On my 1988 3.7lx 180 hp four barrel, the valve cover reads: (wot-4600-4800rpms). You have the two barrel version so I think it should be running wot at around 4200-4400rpms. You may be able to step up one pitch on your prop but you have to make sure that it can still reach the manufacturers wot. It sounds like you have a good engine by what you have stated. Like I said before, these little motors seem to be happy running around 3600-3800 all day long.
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Again, Tom comes through with excellent advice.
Zackie, note that the OEM WOT RPM is a testing RPM to see if your engine/drive are propped correctly.
The OEM WOT RPM is not intended to be a sustained operating RPM.


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I was not using a gps thats what the tach and speedometer said, I don"t plan on running more than 4200 rpm"s, I only opened it up for 30 seconds just to see what it could do. cruised around for about a half hr. at 3800 to 4000, seemed to be happy there. Who know"s if the tach is accurate. will it make a diff. that the lake water is 54 deg? as far as temp. what oil shoud I use? I changed it already using 15w40 diesel oil, but I am going to again 30w or 20w50? I don"t see any gas filter, where would it be? thanks for the info.
 
Thanks again Ricardo, I always try and offer as much information on these engines as I can. They have some quirks as you well know! lol I guess I was not so clear with the info. that I supplied zackie77. Ricardo is right about running engine for a short period of time at wot.
zackie77, what I think you would want to look for with respect to your oil selection is a product with ZDP which has been removed from alot of brands of oils. The 470 has a flat tappet valve train which needs extra protection from friction like most older design engines. I won't tell you what kind of oil select but I will tell you that I use full sythetic 10-w30 motor oil. It is expensive but I feel better about spending the extra money to try and keep the motor strong for a few more years. I will try and answer any other questions you ask to the best of my ability. It sounds to me like you have a good engine. best of luck, Tom
 
zackie77 said:
I was not using a gps thats what the tach and speedometer said, I don"t plan on running more than 4200 rpm"s, I only opened it up for 30 seconds just to see what it could do. cruised around for about a half hr. at 3800 to 4000, seemed to be happy there. Who know"s if the tach is accurate. will it make a diff. that the lake water is 54 deg? as far as temp. what oil shoud I use? I changed it already using 15w40 diesel oil, but I am going to again 30w or 20w50? I don"t see any gas filter, where would it be? thanks for the info.
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Your choice of diesel oil is a good one. Tom has mentioned the flat tappet lifters in this motor. While they are not solid lifters they still like ZDDP (Zinc) to lubricate them. I run Shell Rotella 10w-30w in a C2 Corvette of mine with a solid lifter engine. The diesel oils have a better additive package including higher levels of ZDDP. Brand doesn't really matter.

Dennis
 
5000 rpm sounds a little high man, I would just hit WOT for a few seconds to blow it out but otherwise back off 500-1000 rpms for cruising. Running WOT on any older engines makes me REAL nervous.
 
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