150 black max no power

[boldo]

I have a 84 150 black max on a 18' procraft, it bogs and dies on take off, It bogs and dies when putting boat on trailer. Coughs, spits and sputters while idling. I have took carbs off and cleaned,checked the fuel line, put sea foam in the fuel, changed plugs.Did a compression test ( 110 psi on all cylinders ). you have to keep playing with it to get on plane. A month ago I put new prop on it,25p racker to 25p renagade.
It only turns to 4900 rpms at top speed of 55 mph. I have always had trouble with it bogging. I carry it back when I bought it (12yrs ago) they put used reed valve and block on it. Helped a little still had problems. I have ran it this way for 12 yrs ( thought it was prop).

 

[SpinnerBait_Nut]

Re: 150 black max no power

Merc/Mariner outboard repair forum.

 

[studlymandingo]

Re: 150 black max no power

Is this a new to you motor? If not I would assume this is a new problem.

First thing is to determine whether it is indeed fuel related, or if it is spark related. Pull all of the plugs and see if they all look similar. You will need to be able to check compression on the cylinders. For this you will want a fully charged battery and a compression tester. All cylinders should be over 100 psi and should be within 10% of one another on the readings.

I recommend the purchase of a spark-gap tester; they can be had for about $5 at a local auto parts store. You want to check for a bright consistent spark on all cylinders. If you have spark issues, then there are a number of things you will need to look at: plug wires, switchboxes, stator, trigger, wiring, etc.

Give us as much information as you can.​

 

[boldo]

Re: 150 black max no power

Well I checked out everthing and took the boat back to the lake today still had the same trouble, bogging and dying on take off. Had to keep playing with it to get on plane, after that it ran pretty good
Talked with a machanic, he said mercs. was known for being sluggish and bog out of the hole. Is this true? He said he could help with rejetting, but nut cure.

 

[studlymandingo]

Re: 150 black max no power

My 150 Merc jumps up on plane in just a few seconds; if you are turning 4900 RPMs at WOT, you are severely overpropped or set up improperly. You should be in the 5200-5800 RPM range at WOT. This could certainly make it very sluggish out of the hole. Your A/V plate should be slightly above the bottom of your boat when the motor is level.​

 

[jrampey]

Re: 150 black max no power

I've got the same motor, same year, same horsepower... on an 18' champion. I have a 24p turbo 3 blade prop that will push the boat to 58 gps at 5400-5500 rpm. A little sluggish out of the hole but no problem with bogging. I switch to a 4 blade 19p prop for waterskiing and wake boarding. Wow, really jumps out of the water with the 19p... Have pushed it to 6000 and 50 mph for a few moments before dropping back to cruise speed. Sounds like you have too much prop. Compression sounds good, if carbs are ok - try link and sync of timing and carbs. If still bogs - try power porting the prop. The 19p prop I have has Mercury's PVS plugs already in it - I had to experiment with different size ports to balance the ventilation... too much hole allowed the prop to "breakout" and lose thrust. Too small and the engine couldn't build revs and was slower to plane.

Take good care of that engine and it will reward you with power and reliability. Be warned that having too much prop and lugging the engine will lead to a buildup of carbon over time and result in stuck rings. I read a suggestion here once from Clams... "If top speed is not your absolute goal I suggest that you find a lower pitch prop - something that will give you 5800 rpm wot - but don't rev beyond 5400. Its just a little less strain on the engine.