1987 mercruiser 165hp 3.7

[stonyloam]

Re: 1987 mercruiser 165hp 3.7

Just thinking about this, if it is your hose between the outdrive and the transom, you should not have to pull the outdrive all the way off to clear it, If you just slide it back about 1 inch that should give you enough clearance. If you backflush the water will be coming out of the hole with the O ring on the port side of the bellhousing. Should not have to replace the gasket, just make sure the O ring is back in place when you put it back together (some grease should hold it). Good luck.

 

[krepe]

Re: 1987 mercruiser 165hp 3.7

so i pulled the drive and ran a hose through the inlet and i have good flow so that isnt the problem. i put a cable wire through it also just incase there was something in it. yes, the boat is belt driven with the alternator.

heat exchange is clear, inlet is clear,new pump/impeller,riser is clear,t/stat works and is new.
what else would make me overheat?
thanks,phil

 

[04fxdwgi]

Re: 1987 mercruiser 165hp 3.7

so i pulled the drive and ran a hose through the inlet and i have good flow so that isnt the problem. i put a cable wire through it also just incase there was something in it. yes, the boat is belt driven with the alternator.

heat exchange is clear, inlet is clear,new pump/impeller,riser is clear,t/stat works and is new.
what else would make me overheat?
thanks,phil

Maybe something got into the lower leg intakes before the pump ??????? Do the intakes have screws holding grills on the intakes? If yes, then maybe take the grills off and snake a wire up there and see if anything comes out, like a mud wasp nest or something. Hard to say without being there. Seems as though you have checked about everything else.

Maybe the engine driven coolant pump (Automotive engine water pump). They do go bad, but usually it's a bearing or shaft seal that goes bad, not a flow problem.

One thing to think about, since you are a closed cooling system, gotta think about this like an automotive engine also. Does the "radiator cap" on the heat exchanger hold pressure? I am not sure about the pressure rating, but it should be around 7-14 PSI, I would think. The manual should state what it should be. In a radiator system, if it won't hold pressure, they CAN overheat sometimes because the pressure is needed to "push" the coolant around thru the engine effectively.

Just throwing a couple more "what if's" in there.

 

[stonyloam]

Re: 1987 mercruiser 165hp 3.7

Sounds like that is pretty clear, so you could reattach that hose and try removing the seawater hose from the exhaust elbow, and put in the garden hose and see if you get good flow back out of the bell housing opening, and then try it the other way around. That would check your whole seawater system. With the hose off the exhaust, make sure that fitting is clear. Good luck. The only other place I can think of is in the outdrive itself, the passage in the driveshaft housing, or the tube from the impeller pump.

 

[krepe]

Re: 1987 mercruiser 165hp 3.7

I put a new cap on there also, i was thinking it wasnt holding the pressure but it still overheats with the new one also. My mechanic said he didnt think that enough water was coming out when he hooked it to the ears i dont know if that helps any. I also didnt have the screens on the drive the last time i went out, would that cause me to overheat?
Thanks again, phill

 

[Eric 3.7LX Alpha 1]

Re: 1987 mercruiser 165hp 3.7

Here is a diagram of the water flow for your engine. This thread is confusing as heck. I know you are trying to find a blockage/restriction somewhere in the seawater side of the system. you remove the hose before the voltage regulator and there's no flow there. That's the first thing the water from the drive hits in the engine compartment.

I'm going to get a pic of the voltage regulator so you know what Looks like. If you are not getting any flow (like crazy) on the inlet to the voltage regulator, you have an issue outside the transom.

There's a 90? plastic fitting at the transom where the hose is connected in the bellhousing and I strongly doubt you can fish a wire to make that bend unless you are taking the hose right off inside the transom and can make the bend.

Don't know what happened to my attachment but the pic is tiny gonna attemp to fix it....

 

[stonyloam]

Re: 1987 mercruiser 165hp 3.7

Eric, pretty sure his voltage regulator is no longer there. Would pull hose from transom off of front of heat exchanger.

 

[Eric 3.7LX Alpha 1]

Re: 1987 mercruiser 165hp 3.7

Same as I ^^^^^

Here's the photo somewhat larger. If the flow is weak coming in from the drive there's probably some more impeller blocking it.


Just as a side note:

These 3.7/470 engines are very sensitive to overheating. You can damage a head gasket very easily after an overheat.

You definately want to get a good working gauge on board...

Temps are crucial with these. I have a good working temp gauge and a radiator cap that has a temp gauge built into it as a backup to confirm the dash gauge. (Never had an overheat).

Here's a link to the radiator cap/temp gauge I have:
http://shop.ebay.com/i.html?_from=R40&_trksid=m570.l2736&_nkw=MR+GASKET+TEMPERATURE+GAUGE+

They can be a great running engine thats very good on gas and has loads of torque.

I've had mine for about 10-years and it has needed various work/ maintenance but has always ran good.

You mentioned testing the tsat in boiling water and watching it open, did you also have a thermometer in the same water to see what temp it opened? Just because it opened, doesn't mean it was at the correct temp.

Here's a link to the original Mercruiser repair manual for her, not some partial aftermarket book, good reading and will definately help you along as a boat owner:
#8-for your engine-
http://www.4shared.com/document/zTbCbkDD/Service_Manual_08.html

#6-for your outdrive-
http://www.4shared.com/document/zz_5pj9o/Service_Manual_06.html

 

[dccordell]

Re: 1987 mercruiser 165hp 3.7

Eric, that's a pretty cool radiator cap, think I'll put one on mine too... which one do I need, 13 or 16lb? Everybody with a 470 should have one of those!

 

[Eric 3.7LX Alpha 1]

Re: 1987 mercruiser 165hp 3.7

I love it, not a big fan of the chrome with salt water but have replaced it once and has been nice to have confirmation of the temp.

The radiator cap should have a psi rating on it. Check your existing one and see if there's one.

 

[krepe]

Re: 1987 mercruiser 165hp 3.7

i tried to put water through it before i took off the drive not knowing i wouldnt get flow because it would have to go through the pump and impeller so i took off the drive and i get good flow through the transom and out the lower tube where it connects to the drive so theres no clog there. when i changed the impeller and pump i found old pieces of impeller in where the pump goes, why someone would change the impeller and pump and not remove the old broken pieces i dont know, but im sure i got all of the broken pieces out of there.. maybe not. i did have the drive off 2 times with 2 other seperate mechanics im sure if there was something in there they would have seen it? maybe not, i dont know. i have the drive removed right now but not seperated.. im not a mechanic so i dont want to screw something up, im already having a hard time getting the drive back on. someone told me that with the drive on i should disconnect the inlet hose and i should have an arc of about 6" of water and if not then theres something in the drive, i should have done it while the drive was still on. can i do this with the muffs on or does it need to be submerged in water? i dont know.. rad. cap is brand new 2 days ago. im assuming theres a clog, everyones saying clog, is it a clog in the seawater side? is it a clog in the antifreeze side? i dont know. the wife says i made a bad investment but im not convinced yet lol. i dont know what to do. sigh.
thanks, phill

 

[krepe]

Re: 1987 mercruiser 165hp 3.7

voltage regulater is not there because i have a belt driven alternator. maybe i can take some pics for you guys tomorrow? would that help any? if so, what do you want pics of?
thanks, phil

just ordered a temp guage on ebay also..

 

[stonyloam]

Re: 1987 mercruiser 165hp 3.7

I would still suggest that you reconnect the inlet take the hose off the exhaust fitting, and put your garden hose in there, and see if you get good flow out of the bellhousing. If you do, then it looks like you have a clog inside if the outdrive.

 

[krepe]

Re: 1987 mercruiser 165hp 3.7

by exhaust fitting you mean the exhaust elbow that conects to the back of the riser with the big hose clamps on it? so the exhaust and sea water exit at the exhaust pipe? i could be way off but to me thats what it looks like. thats where the shutter is inside? so basically open it up and stick the hose on top of the shutter and see if i have good flow down right?
thanks, phill

 

[telstar1]

Re: 1987 mercruiser 165hp 3.7

1.Do the flow test with boat in water. Muffs may not deliver enough water to get accurate result.
2.Exhaust elbow/riser IS salt water cooled and could be clogged which will cause overheating.
3.Get your temp gauge working before going any further

 

[krepe]

Re: 1987 mercruiser 165hp 3.7

I checked inside the out drive and all is clear. Im having trouble getting the drive back on. Is there a trick to getting it on all the way? I have an inch to go.

 

[krepe]

Re: 1987 mercruiser 165hp 3.7

i got the drive back on. everything is back together i just need to go buy some grease because some leaked out when i took the drive off. any other iseas besides trying to see if i have good flow coming into the boat through the drive? im going to check that today, im going to bring it to the water and see if i get that 6" arch, i didnt see anything in the drive so this test should check out okay. any other ideas?
thanks, phill

 

[stonyloam]

Re: 1987 mercruiser 165hp 3.7

by exhaust fitting you mean the exhaust elbow that conects to the back of the riser with the big hose clamps on it? so the exhaust and sea water exit at the exhaust pipe? i could be way off but to me thats what it looks like. thats where the shutter is inside? so basically open it up and stick the hose on top of the shutter and see if i have good flow down right?
thanks, phill

No. There should be a hose going from the back of the exchanger to to a fitting on the outside of the exhaust elbow (see diagram). Take that off and put your garden hose in the exchanger hose. That will push water back through the whole seawater system, and out the bellhousing.

 

[krepe]

Re: 1987 mercruiser 165hp 3.7

so i went to start the boat before i trailered it to the water and it didnt start for some reason, this is the first time it hasnt started. i took the wire off of the coil and tried to ground it to see if there was a spark and there wasnt, is there something i did while taking the drive off and back on that i missed that would cause this or is it possible my coil died all of a sudden? ........... this sucks..

 

[stonyloam]

Re: 1987 mercruiser 165hp 3.7

is there something i did while taking the drive off and back on that i missed that would cause this or is it possible my coil died all of a sudden? ........... this sucks..

I don't see how. Yes it does