1982 Mariner 150 wont accelerate in water

[cdoelling]

Ive had this problem a few times now. Put the boat in the water, throttle to full and boat will not accelerate. RPM wont go above 1500 even at full throttle. Motor doesn't sounds like its struggling, just sounds like throttle is only a 1/4 instead of full.

Other days everything works completely fine...... All linkage is going full but motor will not take off. Its not a spun prop, gas issue, compression, etc.

In my yard on muffs, throttle up (only do this for a few seconds) motor will go full and runs fine.

Ive also noticed that problem only happens when there is more than 1 person in boat.

 

[Tankman111]

I was having the same issues with a boat, was checking everything, found out it was sucking air in the fuel line at the fuel tank connection, I installed a short piece of clear fuel line just before the carb's and seen all the air bubbles in the fuel when running, fixed the cracked fuel tank fitting, got soiled fuel in fuel line (no bubbles) and all was well !

All so might be to large of prop. for your motor just don't have the hp to get up and going ?

 

[cdoelling]

I have seen some air bubbles in line time to time (with covers open I can see them in line, I also put on clear when I changed lines). I will have to do some more leak checking.

I haven't changed prop and even with 4 people in boat everything have been fine until recently. I would assum that should rule out prop too big as an issue?????

 

[racerone]

Check for spark on all 6 leads.----In the yard at home even in gear is still neutral as the prop only moves a wee bit of air.---It will wind up on 3 of 6 cylinders !!

 

[Chris1956]

If she accelerates with one person in boat, but not with more, she may be overpropped.

Alternatively, if it is the same prop you have been using before issue, check compression and spark to make sure motor is running on all cylinders and has original power.

 

[cdoelling]

Same prop as before. Just so odd beings some day (last weekend) had boat out by myself she ran 60+ and last night wouldn't go 15mph. Only difference last night was there was 3 of us in boat. We finished fishing and I dropped 2 off so it was just me again. Tried to take off and still no more than 15mph....

 

[Marathon Man]

Stator.

 

[cdoelling]

I checked the stator per the info I could find online and it checked ok.

Over weekend had boat out on river and same issue (full throttle, rpms come up some but doesn't sound full throttle and boat will not go more than 10mph). Went down river with issue and as we were going back up, hit a log or something and all of a sudden motor took off???????

 

[racerone]

Use a timing light to see which cylinders are not firing.