84' black max 150 overheated

[mtduckhunter]

I ran a boat i am looking to buy, we ran the boat about 15 minutes, stopping and going, about 100 yards from the ramp when we shut it down, the motor started making a whistling sound and only steam was coming from the tell tale. we idled on to the ramp and a little smoke was coming from the cowl. When we got home we put muffs on it and the water pump was working fine.

What could have happen?

We did get stuck in mud and grass at the ramp.

 

[Barnacle_Bill]

Re: 84' black max 150 overheated

Running it with muffs does not indicate the impeller is good as pressure from the hose will circulate the water.

 

[mtduckhunter]

Re: 84' black max 150 overheated

Yea i understand that, . . but we ran the RPM,s up a little and it squirted out just as it would if on the water, . . working fine.

My question is, why would it stop working for just a few minutes, and then start working again?

 

[jeffdjpeat]

Re: 84' black max 150 overheated

could be possible the inlet fins got blocked for some reason. i would drop the lower end and check it out to be safe. doesnt take long, and could save over heating the motor next time. better safe then stranded.

 

[hkeiner]

Re: 84' black max 150 overheated

Install a water pressure gauge on the motor and you can be confident that the cooling system is working OK.

http://www.diy-boat.com/index.php?option=com_content&task=view&id=151&Itemid=49

 

[mtduckhunter]

Re: 84' black max 150 overheated

I will probably go ahead and replace the impeller when i get the boat just to be on the safe side.

Im new to the big outboards (70hp was big for me), how hard is it to replace the impeller on this motor? seems kinda intimidating. . .

Im also new to Mercurys, what fuel/oil ratio should i run?

 

[dadgummit]

Re: 84' black max 150 overheated

Mine did the exact same thing today on the exact same engine and year, but I showed good pressure on the gauge. What gives? It was after a long run.

 

[Barnacle_Bill]

Re: 84' black max 150 overheated

I will probably go ahead and replace the impeller when i get the boat just to be on the safe side.

Im new to the big outboards (70hp was big for me), how hard is it to replace the impeller on this motor? seems kinda intimidating. . .

Im also new to Mercurys, what fuel/oil ratio should i run?

They are very easy to replace. 5 bolts. 2 on each side and 1 under the trim tab. Shift linkage is on a splined shaft so nothing to do there. Mixture is standard ole 50:1.