Merc 150 possible failure

[NRAINES38]

1984'ish 150 mercury 2.0 5 pedal horizontal reed blocks, chris carson reeds, cut heads. Havent ran the boat in a few weeks but planned to this weekend. Turning over slower than usually assumed low battery no problem. Always been hard starting after it sits so I use the squirt bottle with premix into the carbs to help her. After a few slow turns it's bust off for a second and shuts down, normal thing till it's warm. After that first fire now it's turning over very fast as it would with a good full battery. A few cranks and she bust off into idle. Instantly hear a knocking/clicking. Baby the throttle to keep it running till warm and notice when I do pedal it a tad there's either a spark, ember or flame (something yellowish red) from the lower port side carb throat. I Instantly shut her down.

Pulled carbs no burn marks, loose material, or obvious signs of something abnormal. Pull plate with reeds and everything is intact. Run the scope down each runner no visible rod/ casing contact or shavings. I can't seem to find any damage. Turns over by hand using flyweel with no grinding or odd noise.

Last trip out it was able to turn 2k more rpms than usual, didn't keep it pinned there but it was possible.

Am I loosing my dang mind or missing something?

[pcrussell50]

Compression and leak down.

Also, starters can be weak. I have a couple 2.0/150’s and a 2.4/200. All of the same generation as yours. For the past two years since I got it, my 2.4/200 was a weak slow start. I began blaming the motor. Until I put on the starter from one of the others. Now it zings up to life like nobody’s business.

-Peter

[NRAINES38]

I plan on compression and leak down tomorrow, wanted to scope every inch before turning it over anymore. Only thing I can find is the bearing on #1 is way different than the rest. Haven't done a rebuild on one of these yet so not sure if that's normal or not.

[skialot2]

All rod bearings are identical. The upper main bearing is unique. But the rods are all identical. If #1 looks different I would take a real good look at it.

Slow cranking is either bad connections or a weak starter. You can almost always take the starter apart yourself and just clean it out. Sand the surface where the brushes contact. Put a drop of grease on the bushings and put it back together and it works like new.

The hard starting is either the enrichner valve is not working or the carbs need cleaning. If the enrichner valve clicks, it's usually working. But you have to check the hoses. They are very small, and they get clogged, or they collapse.

If you have horizontal reeds your motor is later than 1984. Horizontal reed 150's started around 1992 with serial # 0C239553 and later.

[tlwjkw]

If you have horizontal reeds your motor is later than 1984. Horizontal reed 150's started around 1992 with serial # 0C239553 and later.

horizontal reeds were out in '80.. standard on all motors starting in '91... just cause it has 'em doesn't necessarily mean it came with 'em....

[NRAINES38]

A majority of this motor is not original. Carbs, front half, reeds, heads, exhaust tuner, mid. I'm not worried about the hard start at this point. I mentioned it because it seemed like something was tight and then loosened up allowing it to turn over faster.

On the bearings I busted out the crayons and drew a picture. It is not to scale but what I'm seeing. 2-6 the cages extend just short of the bearing face and are all evenly spaced. I am watching them individually as I turn the motor over with a bar. On #1 the part of the cage that divides the bearings is noticeably shallower and has wear marks on the faces, not sure how but the marks are visible. Also at a certain point in the rotation there is 1 space that is wider than the rest with the split. I know they're supposed to be split just odd it's visible.

[NRAINES38]

[tlwjkw]

some of tha cages were justa little different (more noticeable at tha split) dependin' on who made 'em but maybe time ta take it apart ta be safe.....

[rock]

If you hear a knocking noise, tear it down before you need a new crank. Just rebuilt one with a knocking noise and had to replace crank, one rod, all pistons, and a rod. Knocks in 2 stroke engines will be terminal if not addressed. JMO.

Rock

[skialot2]

horizontal reeds were out in '80.. standard on all motors starting in '91... just cause it has 'em doesn't necessarily mean it came with 'em....

Yes, Horizontal reeds were used on 200's all throughout the 80's. I was referring to stock 150's. Once you are referring to modified engines, all bets are off. It is now no longer a 150. Could be anything. There is no telling who did what.

[pcrussell50]

All rod bearings are identical. The upper main bearing is unique. But the rods are all identical. If #1 looks different I would take a real good look at it.

Slow cranking is either bad connections or a weak starter. You can almost always take the starter apart yourself and just clean it out. Sand the surface where the brushes contact. Put a drop of grease on the bushings and put it back together and it works like new.

The hard starting is either the enrichner valve is not working or the carbs need cleaning. If the enrichner valve clicks, it's usually working. But you have to check the hoses. They are very small, and they get clogged, or they collapse.

If you have horizontal reeds your motor is later than 1984. Horizontal reed 150's started around 1992 with serial # 0C239553 and later.

I replaced a tired starter with one from another motor. I was going to drive across town (Las Vegas, BIG town), to the starter and alternator shop. But I think I’d rather do what you suggested first. Thanks. If it ends up being bad windings, then I’ll take it to the shop.

-Peter

[skialot2]

Ok, Thinking more. There are 3 types of rod bearings that I know of. All the bearings have split cages. The early metal cages had loose bearings. You had to put each roller in the cage as you assembled the motor. The later metal cages the rollers stay in the cages. Then there are also plastic caged bearings. It is recommended to change them to metal. Your #1 probably has a loose roller bearing and the rest probably have the caged rollers. But if you have a knock, you need to figure out what that is. Or did the noise stop and now you get 2K RPMs more? 2K is a lot. But sometimes things run really good right before they go POP! LOL Good luck

[skialot2]

I replaced a tired starter with one from another motor. I was going to drive across town (Las Vegas, BIG town), to the starter and alternator shop. But I think I’d rather do what you suggested first. Thanks. If it ends up being bad windings, then I’ll take it to the shop.

-Peter

Mark the end caps so you can easily put them back in the same position they came off. Make sure the brushes are not stuck. Be careful of the springs. Make sure to sand the brush contact area even if it looks clean. It's not. To reassemble I found it easiest to put the bottom end cap down on a table. Drop the armature in while positioning the brushes in place. Then while holding the armature down on the brushes lower the case carefully over it. It's a strong magnet so hold tight. Make sure the brushes stay in place. Once you do it a couple times, it's really easy.