Spare parts Merc cruiser 3.7 - Now Dying On The Lake

[karayj]

I’m doing some troubleshooting and rather than buy new parts I’d rather replace it with something known good I have a temperature issue and it could be the switch heat to buy one if it’s not the real problem my old switch is definitely gone I’ve put an aftermarket one in but my gut feeling says it’s registering incorrectly and making it look like the engine is overheating. I’d like to get the right one in there so I can aluminate a false read.

 

[Bt Doctur]

maybe, maybe not, how old is the impeller, how old is the thermostat, are you using 50/50 AF mix, normal temp is around 165-170
If 20-25 bucks bothers you .your in the wrong hobby

 

[Scott Danforth]

first, spend $10-$20 on an IR temp gun from amazon

second, its a 470 mercruiser. if a fish swims past the oil pickup and farts, it will cause enough of an imbalance in the cooling to potentially have an issue. (covered many times)

if your impeller is not new - change it
if you havent cleaned out the HX - clean it
if you havent serviced the coolant - change it

if you so much as slightly over heat the motor just once, it will spit the head gasket and you need to tear the head off, and replace it.

 

[jbcurt00]

karayj please remember Iboats doeant have a swap, trade or used parts section

Solicitation removed

 

[achris]

second, its a 470 mercruiser. if a fish swims past the oil pickup and farts, it will cause enough of an imbalance in the cooling to potentially have an issue. (covered many times)
....

Oil pickup? He means water intakes on the drive...

All the rest, yep. :thumb:

Chris...

 

[Scott Danforth]

meant water pickup..... LOL

there may have been beer involved

 

[achris]

meant water pickup..... LOL

there may have been beer involved

There should always be beer involved...

 

[karayj]

Stalled five minutes after test run

Stalled five minutes after test run yesterday for the first time I put my boat that I purchased on the lake. Now prior to going to the lake I did run it a few times to make sure the temperature was good other things were fine and when I did run it I ran it for about I don’t know 10 minutes. Yesterday we got on the lake it took me a couple times to start it up I let it idle and we started going about two or 3 miles an hour slowly out. I started to drop the lower unit and give it some gas and I heard a rumbling noise fishfinder was not working well guess what I was hitting bottom . I corrected that and we got into deeper water where I started dropping the lower unit and I gave it some gas we ran for about 45 seconds to a minute things were doing great then there was some sputtering it felt like I was only driving on three cylinders not quite sure. I started it up again and said it’s time to head back and during that process after about 10 seconds it died again this happened two more times. I decided it’s best just to idle back in I was able to idle for about 45 seconds on three separate occasions and then nothing ever again I had to pedal all the way back so two things come from this it felt like I lost the cylinder but definite fuel situation yes the tank was three-quarter filled and when we got back I opened up the gas cap and shock the boat and you could hear fuel in there. The reason I’m writing this today is where should I start and what should I look for I’m a car mechanic I have some experience With boats my fear is that it starts right up and it’s going to be one of those things were in the driveway it runs fine but once you go on the lake I have problems

 

[Grub54891]

What boat, mostly motor setup. Change fuel filters, see if you have water or debris in the filters. If carbureted , fuel pressure should be 5-7 lbs. Engine serial numbers help us a lot in diagnosing.

 

[Bondo]

The reason I’m writing this today is where should I start and

Ayuh,..... What motor, drive, 'n vintage is a good place,.....

 

[karayj]

well it tunes out these boats take at lest 15min to warm up so I just needed to wait a bit.
The switch did more but the boat stalled on the 1st real test run on a lake . Then I could only idle in and that ended after 4 min so I had to paddle in. YUK !!!! I started the boat today started right up but allot of blue and black smoke (unburnt fuel. Feels like it's running on 3 cylinders.

 

[karayj]

Engine serial is OC520420 sorry guys 89 merc 3/7 . stated right up today but like at the boat ramp lots of smoke at startup. Unburnt fuel smells like , I will work more on the weekend to see what cly is not running. This smoke is all new .Last week when I was running it to make sure is does not over heat it started clean. Side note the lower unit go hot after 45 seconds of running right

 

[GA_Boater]

Combined both threads cuz as you can see we'll ask the same questions again with two threads.

Did you address the overheating problem or decide the sender was bad? Did you change the impeller?

What do you mean you lowered the drive? Are you starting the motor with the motor all the way up or past the trim limit?

Have you changed the lower unit lube?

It seems you are skipping some of the things that need to be done for a new to you boat.

 

[karayj]

1st THANK YOU ALL for you patience dealer with some dumb psot by me. It 's been a while 10 years since my last boat. 18 ft Sea Sprite 4.3 a great boat.As far as the stall I may have gotten it figured out >>> Stuck choke oen the motor warmed up she satlled ans clulou not run without air in the carb.What I should have done is taken the aire cleaner off look the the flap and and see if it was stuck closed.
I will test it this weekend on the lake on a one last test run before winterizing
The sender is fine tested it with a ohm meter. Turns out these boats take about 10 min plus to warm up.
This thread can be closed Thank you all for your tips and help

 

[QBhoy]

Hi

i know a great spare part for these. It’s a 3.0 swap out, only joking...sort of.

please don’t kill me...but temptation was too great. I had a real time of it years ago with a couple of these.

 

[GA_Boater]

We don't close threads because others can't learn from closed post.

 

[Tycer]

1st THANK YOU ALL for you patience dealer with some dumb psot by me. It 's been a while 10 years since my last boat. 18 ft Sea Sprite 4.3 a great boat.As far as the stall I may have gotten it figured out >>> Stuck choke oen the motor warmed up she satlled ans clulou not run without air in the carb.What I should have done is taken the aire cleaner off look the the flap and and see if it was stuck closed.
I will test it this weekend on the lake on a one last test run before winterizing
The sender is fine tested it with a ohm meter. Turns out these boats take about 10 min plus to warm up.
This thread can be closed Thank you all for your tips and help

How did the test run go??

 

[karayj]

I have another post going I’m used to doing automotive post a little bit different than here sorry guys for causing a lot of confusion.
It turns out that the impeller is totally toast is that why the boat stalled I’m not quite sure I’m still trying to learn this engine. My plan right now is to get an impeller kit
I’m still trying to decide what kind to buy whether you just buy a kit with the impeller or with the water pump and all the gaskets and O-rings after that’s done I will update everyone here