1987 mariner 150 horse NO POWER

[Ryan618]

I'm back again unfortunately. I went out on the water yesterday, engine fired up just fine as usual, idled great, cruised through the no wake zone smooth as could be but as I went to take off I had NO power at all, couldn't even get up on plane. I checked the primer bulb and it was firm, I recently put in new plugs, correct according to the manual NGK BUHW, put a new fuel filter on (had some bogging issues last week), sprayed the carbs with carb cleaner and on muffs it ran great, throttle responded quickly out of gear but as soon as there is a load, no power, ran along at a top speed of 11 mph, strange thing is after about 10 minutes of that it started surging then cutting out again, eventually it planed out but topped out at 25 mph. I ran up and down the lake for about 15 minutes hoping it just needed ran out a little but as soon as I shut it down and tried to take off again, same thing, no power. I just got this boat a couple months ago and according to the previous owner it had only been ran a handful of times the last couple years, maybe twice this year before I got it, its been running great since my last post bit I am at a loss now. Ive talked to several people and get varying opinions what the problem could be, the only consistent diagnosis is a fuel delivery issue. I've read a couple posts about cleaning a screen out, not sure where that is and the manual is a little confusing, it's showing a lot of different engines it the diagrams, another thought was the fuel pump. Can these pumps be rebuilt? Compression is good on all 6 cylinders 115-125, I inspected all the wiring to the electronics and seems to be in good shape, no breaks or corrosion, I have good spark as well at each cylinder.

This motor is on a 1986 cheetah fish & ski, 19'6" with a 23 pitch prop, I would think with this setup i should be running around 50 mph at WOT but according to the speedometer and GPS it as topping out at 35 when it was running "well", after determining that the speedo was correct I was worried that something wasn't right and apparently something wasn't right. I do have a factory manual so hopefully can rebuild carbs and sync them on my own after reading some of the horror stories about going to a shop for repairs multiple times.

Any tips or ideas will be most appreciated, thanks.

 

[jerryjerry05]

Re: 1987 mariner 150 horse NO POWER

Spark test.Gap tester should be 7/16"
Fuel system:Ethanol is messing with a lot.
Check the fuel pump diaphram.Check the carbs for crud.The hoses could be soft and collapsing.Look into the system.J

 

[j_martin]

Re: 1987 mariner 150 horse NO POWER

Start with a compression check to be sure you haven't done some severe internal damage. One of the quickest ways to burn down this engine is to push it when it's starving for fuel.

If compression is good, check for a strong spark on all plugs. If that's good, go after the fuel system.

 

[MFisher]

Re: 1987 mariner 150 horse NO POWER

Another thing that I would check is make sure that you have consistant firing on all the plugs, you could have a weak ignition box for one side of the motor. I ran into a simaliar problem earlier this year. The motor would idle fine on muffs and could even bring the rpm's up with no load on the prop, but as soon as it hit the water the same problem happened. What cured my problem was these two things that I did. 1st I rebuilt the 3 carbs, very easy and straight forward. 2nd I replaced the ignition boxes for both sides of the motor, then linked and sync the carbs a bit of a pain but that seemed to fix the problem... Also if you do decided to rebuild the carbs do your self a huge favor and replace every rubber hose on the or going to the motor.

Hope this helps And I would like to say thanks to everyone that has answered any of the questions I have asked.

 

[Ryan618]

Re: 1987 mariner 150 horse NO POWER

Thanks for all the tips, I'll let everyone know how it works out once I tear into it