96 Mariner Magnum 3, 150hp: Quick Help/UPDATE

[will941s]

1996 Mariner Magnum 3, 150hp OB, 0G383790: Was hard to start when cold, and the heads seemed hot. I installed the new water pump kit, and whoever installed it last used the wrong gaskets in the wrong places, as well as did'nt remove all the parts of a previous failed impellar. I cleaned all that out, and put all new everything in. I installed a new Fuel pump kit, no more gas dripping everywhere. It starts easier, and pees almost right away now.

Heres the deal, the heads are cooler now.....but still seem a little hot. I can touch them for about 2 or 3 seconds then I have to pull my hand away. Pee stream is better, but then I removed the t-stats and re-installed the covers and now it pees like a race horse, and heads are WAY cooler. The t-stats did'nt seem to look to bad, and they open freely. Question is, how hot should those heads be with the stats in? Is the 2 or 3 second rule ok? Or should I be able to hold my hand on it for a long period of time like I can without the stats?

 

[Texasmark]

Re: 96 Mariner Magnum 3, 150hp: Quick Help/UPDATE

Normal setting on a US domestic hot water heater is 140F. Stats are stamped 143F for opening which means that water can get hotter before they are fully open. If your tell tale is plumbed off the output of your stat housing, then to get any appreciable stream, the stat has to open first. Otherwise you get a good stream immediately....easy enough to follow the tubes to see what you have.

If you pull the stats, the powerhead may not fill completely with water and the top of the enigne will not get cooled.

 

[will941s]

Re: 96 Mariner Magnum 3, 150hp: Quick Help/UPDATE

It's plumbed from the housings, and what was getting me is when it was warm, I know the stats were open from all the steam out the pee hole, but it would'nt pee at idle. Thats what led me to think it was the impellar. I replaced that, but found parts of a previous water pump stuck in the base. The water pump impellar I took out was actually in pretty good shape. Now I'm beginning to wonder if I should pull the Lower again, and reverse some water flow through the block and see if anything comes out the water jackets.....like more parts of the pump that failed. What do ya'll think?

 

[Texasmark]

Re: 96 Mariner Magnum 3, 150hp: Quick Help/UPDATE

If plumbed from the housings, you basically won't get any pee till the stats open. It seems like an eternity, waiting for them to open, but there is a caveat here. You have an overtemp sensor and alarm and if they don't open you'll know it, or if both don't open.

Mark

 

[will941s]

Re: 96 Mariner Magnum 3, 150hp: Quick Help/UPDATE

It has the sensor, and it does give the overheat and low oil beeps when you turn the key, but nothing goes off when it's running, which I guess everything is alright. How do you test the alarm? I took the lower back off today, and ran water through the t-stat holes, and the fresh water washdown hole and nothing but a few little pieces of crud came out the water pickup tube. I could hear the water in the crankcase through the t-stat holes, and water came out both holes when you put water in one, do I assume all passages are open. It did'nt seem restricted anywhere. I guess I will throw in some new t-stats and call it a day. What do you think?

 

[j_martin]

Re: 96 Mariner Magnum 3, 150hp: Quick Help/UPDATE

I think if you touch the heads and you don't leave skin on em, they aren't overheated.

This big V6 has about a 2 million BTUH fire going in it, with a step-staged cooling system. operating temp will vary from about 130 to 200 under different conditions and be just fine.

 

[will941s]

Re: 96 Mariner Magnum 3, 150hp: Quick Help/UPDATE

Thanks for the replies, I guess all is well in 2.5L 150, v-6 world and I will stop stressing so much. I got the boat at a unbelievable deal at $3,900 for a 1999 Key West 1900 Sportsman, and it's in near new shape. The alarm has never gone off, and it has a new water pump, and fuel pump....and I will throw in some stats, that alone should help me take my mind off of it. I'm used to my old Merc 25, that feels cool to the touch...I guess I was expecting this one to be like that too. Now I can get back to work on my 115hp Johnson spl.