85 Merc 150 Black Max

[jbdyess]

Have a 85 150 Black Max serial# 06568378. It is having a problem getting out of the hole. It seems to happen most frequently on warmer days (55+) and with another person in the boat. When I am alone, it rarely has a problem. When it does have trouble, the RPM's are at around 2000. When it finally gets on top, the RPM's jump to around 4800. I usually have to mess with the tilt on the motor in order for the boat to get up. In the worst cases, the person I am with has to move to the front of the boat. I went out in January with the air temp around 28 and it did fine all day long with another person in the boat. It would be greatly appreciated if anyone has any suggestions.<br /><br />Thanks- B.D.

 

[LubeDude]

Re: 85 Merc 150 Black Max

Well, if the best RPM you can get is only 4800, and the engine is running on all 6, then you are seriously over propped, Do you know what prop you are running?

 

[jbdyess]

Re: 85 Merc 150 Black Max

It's a 3 blade Quicksilver 23 pitch

 

[Barnacle_Bill]

Re: 85 Merc 150 Black Max

Either you are running that on a very heavy boat or you are not hitting on all 6 cylinders. I have an 83 150 on a 16 ft bass boat. Trimmed out, it tachs around 5800 and the prop is a 14.25 X 23. When I first got the prop, I had a lousy hole shot with 2 people in the boat. Increasing the ventilation holes to 5/16" took care of thaqt problem.

 

[lmoreau]

Re: 85 Merc 150 Black Max

Do you know how to properly use the trim on the motor? Trim down all the way for takeoff, then start trimming up after you get on plane.

 

[WillyBWright]

Re: 85 Merc 150 Black Max

Is this a new situation? I can see that prop working on a bassboat or other similar hull, especially if you're about maxed-out for Hp. Check your sparkplugs. They should all be dark brown and slightly oily. If any are drastically different than the others, we can help you find out why.

 

[CU2NITE]

Re: 85 Merc 150 Black Max

If it's an XR2, the max rpms is 6000 at full throttle. I rap mine out at 5800 and run around 60 mph. I use a 21 pitch 3 blade on a 17.5 foot bass boat. Good luck and let us know.<br />CU<br /><br />---------------------<br />RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

 

[prolinews]

Re: 85 Merc 150 Black Max

Did it ever run right?

 

[jbdyess]

Re: 85 Merc 150 Black Max

I have been having the problem for about a year.<br /><br />Willy - 5 plugs were dark brown and slightly oily. 1 plug had quite a bit of carbon buildup . The boat is a 17ft Tide Craft bass boat. I took the silencer cover off of the carbs and there was a pool of fuel/oil mixture sitting in the bottom of the cover. Is this normal? Could there be a flooding situation going on? I also notice a large fuel/oil slick behind the motor when I stop.

 

[prolinews]

Re: 85 Merc 150 Black Max

sounds like a carb kit is going to help your problem . Do a compression test first replace plugs and try it out .I would also do a pump kit.

 

[prolinews]

Re: 85 Merc 150 Black Max

does it leak gas everywhere when you pump the bulb?

 

[jbdyess]

Re: 85 Merc 150 Black Max

Proline-<br /><br />No it does not. I just checked that this afternoon. I pumped the bulb until It would not pump any longer. It did not leak anywhere.

 

[WillyBWright]

Re: 85 Merc 150 Black Max

I'm leaning towards a fuel pump. There are two chambers and each is driven by crankcase pulses. If one develops a leak, that cylinder will run rich. If it's never been done, it's way overdue. Kits are cheap and the job is fairly easy with regular tools.

 

[LubeDude]

Re: 85 Merc 150 Black Max

Originally posted by flpounder:<br /> I took the silencer cover off of the carbs and there was a pool of fuel/oil mixture sitting in the bottom of the cover. Is this normal?

Yes, I think it is, I think its from tilting the engine up for trailering, mine does it also and my carbs are rebuilt.<br /><br />The more I see what others are running for props with there 150,s, Im becoming convinced that my engine which has 150 decals on it is in fact a 175 as per the carb #s. My boat is 18', and I can turn a 25P High Five at about 5,800 @ about 60 MPH and a 14.75 27 four blade @ 5,400 a bit over 60.

 

[jbdyess]

Re: 85 Merc 150 Black Max

What should the compression be?

 

[LubeDude]

Re: 85 Merc 150 Black Max

Originally posted by flpounder:<br /> What should the compression be?

Mine runs 120#s all the way accross. Its just as important that you dont have one or two that are more than about 10 #s different. If they are, sometimes a good decarb will even them out.

 

[jbdyess]

Re: 85 Merc 150 Black Max

Thanks for all the help. I will check these out and let you guys know the outcome.

 

[KCLOST]

Re: 85 Merc 150 Black Max

Check the spark, just to make sure...

 

[jbdyess]

Re: 85 Merc 150 Black Max

Thanks KC. I will do that.

 

[heybaylor]

Re: 85 Merc 150 Black Max

check your scavenger/bleed hose's , also the check valves that they hook to. they go from each cylinder intake into the checkvalves behind the carbs( you should be able to suck out of the hose , but cant blow in .from the cylinder end.(a baby syringe is better than your mouth..gasp /spit /hate that taste) <br />they are supposed to suck the "puddled fuel/oil<br />out of the intake manifold and recycle it through the intake ports.<br /><br />if ok ,then you may have a reed leaking ..that will cause puddling in the/a carb venturi at idle <br />and "suck" it in that cylinder when you apply throttle ..either one will cause a plug to misfire untill it burns off the excess fuel<br /><br />by the way , there is a "valve at the bottom of the airbox hooked to one of the "checkvalves, that is supposed to suck out the fuel that drips out of the carbs when you tilt it .<br /><br />if you pump the fuel up just before you take off that will tell you if it is a weak fuel pump.<br />if no change , pump is prolly ok