mercruiser 485 confused

[popsmazz1]

ok here goes, bought a 1990 larson 19ft. boat, the problem is I didn"t research it b4 I bought it. I now know of all the possible problems with the 3.7 liter 470"s, but in my research it looks like a 485 witch is in mine doesn"t belong there, looks like they were only made fron 1980 to 1982. looks like I got screwed. the motor does run, but it has a 2 barrel on it and its supposed to have a 4 barrel, am I right? the boat is in very good shape, should I put the alternator and electronic ignition kits on it or leave it stock? the # on the engine is 6180267, any suggestions?

 

[Don S]

Re: mercruiser 485 confused

The 485 came with a 2bbl carb, the 488 in 83 and 84 was the first to use the 4bbl carb.

 

[stonyloam]

Re: mercruiser 485 confused

It sounds like someone put in a replacement engine. That should be no problem because the block is essentially the same as the 90 would have been. The question is, does it have the newer type exhaust reservoir and aluminum exhaust manifold along with the 4" heat exchanger? I would not worry about the electronic ignition or alt just yet. The points will work just fine for getting it running (on muffs), and if the system is charging you can wait till it fails to make the change. Couple of things that you need to do are get it running and do a compression check and cooling system pressure test. That will tell you the overall health of the engine. Also while running check for coolant leaking from the weep hole on the lower starboard side of the engine water pump. On the outdrive change the impeller. Any problems there are lots of 470 guys here to help. Welcome to the club.

 

[popsmazz1]

Re: mercruiser 485 confused

ok thanks, the engine does run and I don"t see any coolant leaking at this time. I bought from a marine repair shop and he said he checked it out, and he garranties it"s ok. I will check back when I get a chance to take it out, come on spring.

 

[popsmazz1]

Re: mercruiser 485 confused

how do I tell if it is a 3" 4" heat exchanger? do I measure it somewhere?

 

[Don S]

Re: mercruiser 485 confused

It's the diameter of heat exchanger.

 

[popsmazz1]

Re: mercruiser 485 confused

ok, looked at it today, it has a 4" heat exchanger and an aluminum exhaust manifold and intake manifold, is that good? compression all rite around 150 on a 4 cyl, should be ok I think, thanks for the info, keep it coming.

 

[Don S]

Re: mercruiser 485 confused

Should be good to go, the manifold is part of the closed cooling system and has antifreeze in it. So aluminum will not be a problem.
If you don't have any history on the maintenance, I would sure be looking at pulling the drive, replacing the raw water pump impeller, inspecting the bellows, alignment, gimbal bearing, ujoints, greasing the coupler, before putting it in the water. The last thing you want to do on any 3.7 is an overheat. That can easily turn into a head gasket replacement.

 

[popsmazz1]

Re: mercruiser 485 confused

shop I bought it from said he did replaced the bellows and raw water impeller, he said to bring it back in the spring and he would change the coolant, and check everything b4 I put it in the water, part of his " guaranty".

 

[Don S]

Re: mercruiser 485 confused

Sounds like you should be ready to go.

 

[popsmazz1]

Re: mercruiser 485 confused

thanks for all your info, at least now I have some idea what to look for.

 

[popsmazz1]

Re: mercruiser 485 confused

I need some advise, started it up today on muffs, runs good, good oil pressure, but the temp. gauge got to 175 so I shut it off. I let it cool off and tried it again, I see steam coming out of prop area but not much water. temp up to almost 175 so shut it down. do you think it needs an impeller or maybe thermostat? I think shop may have told me a tall story and didn"t do crap. you guys know way more than me.

 

[stonyloam]

Re: mercruiser 485 confused

The operating range for a 470 is between 165 and 200 degrees F. You probably have a 160 thermostat, so 175 is not hot by any means. Exhaust comes out of the prop area, so steam is to be expected. If the temp stabilized at 175 I see no problem. Feel the heat exchanger while it is running, if the exchanger stays reasonably cool, your impeller is probably OK.

 

[popsmazz1]

Re: mercruiser 485 confused

the heat exchanger felt kind of warm to the touch, I don"t know hot hot its supposed to be, I could touch it and not burn myself, kind of like a car radiator, what scared my was alot of steam. of course the water on my hose was probably 40 deg. and the outside temp. was 45.

 

[stonyloam]

Re: mercruiser 485 confused

The cold water from your hose comes into the forward end of the exchanger (should be cold) and flows through a bundle of tubes on the starboard side to the back then through center tubes to the front and finally through a bundle of tubes on the port side to the back where the water exits through a tube up through the power steering cooler (if you have one) into the exhaust elbow where the water mixes with and cools the hot exhaust gasses as they are leaving the engine. So on a cool day it would not be unusual to see steam. The antifreeze flows back to front around the tubes and is cooled by the water flowing through them. The main thing is that the temperature stabilizes after running for a while. If did not have sufficient flow of cooling water through the exchanger it would get very hot, way too hot to touch.

 

[popsmazz1]

Re: mercruiser 485 confused

ok, tried again today, temp goes up to 175, as far as I will let it go, I think it will keep going, the heat exchanger got to hot to touch, I was wrong on my last post, time for an impeller I assume, going to call the man today, he said all was well, he lied, assuming he won"t honor his gaurantee, what shoud I expect to pay for impeller replacment?

 

[stonyloam]

Re: mercruiser 485 confused

You know I have been thinking about it, and I guess if the engine were up to 175 the exchanger would be pretty hot, but 175 is well within the proper operating range, you need to see if it stabilizes, and you need to make sure you are feeding enough water through the muffs. The impeller is a pretty easy job, and would be something that a mechanic would do on a routine basis, so I would not assume that you were lied to. On muffs you should not run it above about 1100 rpm, as the hose may not me able to deliver sufficient cooling water.

 

[popsmazz1]

Re: mercruiser 485 confused

took the boat to the man today, they changed the impeller old one was totally shot, he apolagized and said he thought he had done it last fall, now it runs below 150 deg. ran at 1500 rpms for half an hour on muffs. heat exchanger barley warm to the touch. so looks like all is well. going to flush coolant tomorrow.

 

[popsmazz1]

Re: mercruiser 485 confused

when I got home from the repair shop I noticed the bellows I think it"s the exhaust bellows came loose from where its clamped from up by the transom, I managed to get it back on and tighted the clamp through the hole in the outdrive, not easy to do, my question is how do I know if it"s on properly? I think it came off when I raised the drive to the trailer postion

 

[popsmazz1]

Re: mercruiser 485 confused

just to update if anyone cares,I guess I got the bellows on ok, took the boat out today and it ran perfect, temp. never went past 150, ran rpms up to 5000 for a short time at 45 mph. I think that may be a little to high on the rpm"s ?. don"t plan on running that hard anymore sounds good cruising about 4000. anyway no leaks and ran real smooth.