86 Blackmax 150 Bogg on Acceleration, Out of Money/Time/Patience/things to replace

[snowbrd84]

Long post here, but I have read at least 500 pages of posts and troubleshooting guides over the last 3 months, so here it goes.

I have a 1986 Mercury Blackmax 150 XR2 on my 18' bowrider with neverending issues. I have put so much money into this motor that I am sunk at this point, unless I can figure this out, I will be forced to sell the boat at an extreme loss and try boating again in a couple years when I can maybe just buy one with a new motor which is pretty sad since damn near every part on this motor is new now. Id be half way to just buying a 4 stroke at this point if I could have all that money back... I am pretty mechanically inclined, but this has me at a complete loss. Have had several friends look at it, one who has worked on 2 strokes his whole life, no one has a clue.

Rebuilt the motor over the winter after the #6 piston and lower main bearing turned into shrapnel last fall. Block looked good, no scoring, had the cylinder honed and bought brand new piston, all new rings, and new gasket kit for whole motor. Replaced the head cover since it was damaged. This whole summer I have been fighting this motor. First start of the day it fires right up and idles perfectly with no issues. Goes right into gear and will cruise at no wake speed all day long. No overheating, no strange sounds, nothing. As soon as I go to give it full throttle, it boggs out. Can be saved by backing off the throttle usually. It seems that the faster the attempt at WOT, the more likely it is to bogg out. As in very slow acceleration will sometimes result in it taking off and reaching WOT. But sometimes, it will just get up and go right from neutral to WOT with little hesitation. 9 times out of 10 it just boggs out. It seems like once it is past a certain RPM, maybe 2500 or so, it will accelerate all the way to WOT every time. Once at WOT, it will run all day and power is not an issue whatsoever. I have tried pumping the primer bulb when it is bogging and it has no effect at all, so I do not think it is a lack of fuel. Hitting the enricher when its bogging causes it to bogg more and die out. Sometimes if I pump the throttle lever back and forth, it will all of a sudden kick in and take off. DVA checks out on all the electronics which are all brand new at this point. Sometimes it will bogg out and start right back up, but then sometimes it will be very very hard to restart.

Given how perfect the motor runs once it gets going, this has to be something small/fixable that I just can't diagnose.

Things Done So Far: I think some of the things have helped, as in it is slightly easier to get it to get going, but in the end, the problem always comes back.

Fuel pump rebuilt twice
Compression test shows 115-120 psi on all 6 about 10 minutes after running
All new NGK BU8H plugs
New CDI Stator - 16amp
All new plug wires
Both switch boxes replaced
Wiring double and tripple checked
New rectifier
Flywheel checked, 16-amp flywheel, no loose or missing magnets
Trigger is advancing properly
Good spark on all 6 cylinders, even when bogging
Idle stabilizer, spark advance, and oil injection removed
Timing reset at idle and then at WOT to 23deg to account for spark advance removal
Carbs taken completely apart and cleaned, cleaned, cleand, and then cleaned, two different times
Carb floats set flush with gasket surface when upside down
All jets are correct size
Link and sync procedure 4 or 5 times to confirm
All new fuel line, correct marine fuel line, from tank to motor, and throughout motor
All new filters, clear filter between pump and carb shows no bubbles
New primer bulb
Anti-siphon valve removed from tank
Checked all recirulation check valves and hose routing


Possible Issues?

During rebuild, some reeds were not completely sealingper factory spec, so I flipped them all over, they were white plastic, not metal, so aftermarket I am guessing. Should I not have flipped them? Could this be a reed problem?

The upper exhaust ports sit just at the water surface since this motor is a bit heavier than the 90 it replaced. Sometimes they are submerged, the AV plate is dead level with the bottom of the boat. Could submerged exhaust releif ports be an issue?

I replaced the stator with a good used one when rebuilding, but I am not entirely sure it is rotated/oriented exactly as the original one was since I threw the old one away and didnt mark how it was positioned. I have since bought a brand new CDI stator to eliminate the stator as a problem, but I am still not sure it is oriented in the exact some rotation as the original, it coule be 1 or 2 holes rotated, no more than that since the wires still come out of the stator in the same general area to the left of the starter and above all the electronics. Can not find a single picture on the internet clearly showing the proper position, does this even matter?

With about 4 hours on the new plugs, they still looked shiny clean, I know nothing about reading spark plugs, should they look clean after 4 hours?

Realized I have been running off of a deep cycle battery, I never see above 12.8v on the digital volt gauge, even with new stator and rectifier, it does have a voltage regulator that is original. Should I be seeing higher voltages?

 

[snowbrd84]

Also, I have read found/read 5-10 other threads on various sites/forums with what sounds to be the EXACT same issue. Problem is, not one single one of them has ever come back and provided the solution. 5-6 page threads that just end with no final word...

 

[SkiDad]

I'm very sorry to hear that. You did more than 90% of people would have done. I guess you might be best to part it out and get some of your money back. But you might get better prices in the spring for the parts. I know a dealer near me that has that engine for sale and I wonder if you should look at having a local dealer put one on for you and rig it etc and have some kind of guarantee that is works from the get go.

 

[Dukedog]

Sounds like a carburetor problem of some sort. Sometimes ya run across a couple that no mater what ya do they just won't work. Reeds and/or bleed problems usually show up at idle with motor loading up. Have you checked max timing at crankin' speed? All plugs out with number one in only if necessary. Doesn't have ta be long as its grounded Be sure tha others are grounded and away from tha holes. What was tha number? Was it steady? Double check trigger wires for easy movement on top of tha block behind flywheel......

Tha motor is to low if cav plate is even with bottom for sure. Ta do any motor height changes a water pressure gauge is really a must have. Jack plate or bolted straight ta transom?

 

[snowbrd84]

Sounds like a carburetor problem of some sort. Sometimes ya run across a couple that no mater what ya do they just won't work. Reeds and/or bleed problems usually show up at idle with motor loading up. Have you checked max timing at crankin' speed? All plugs out with number one in only if necessary. Doesn't have ta be long as its grounded Be sure tha others are grounded and away from tha holes. What was tha number? Was it steady? Double check trigger wires for easy movement on top of tha block behind flywheel......

Tha motor is to low if cav plate is even with bottom for sure. Ta do any motor height changes a water pressure gauge is really a must have. Jack plate or bolted straight ta transom?

The first thing I did on the water was set the low end timing then pulled all six plugs, grounded them, put it to WOT, and set the timing to 23 deg while cranking since I removed the spark advance. Very steady at 23 deg. Was at about 21 before adjusting .

I am really leaning towards the motor being too low and the exhaust relief ports getting submerged as the issue. After rebuilding the carbs, I took it out by myself and it seemed to work really well, only bogging a couple times. The next weekend, took out a couple friends, had real trouble getting it going. Then this last weekend, me and one other friend took it out, and it seemed sort of half way in between...

So it sounds like I should raise the motor a bit. Do I really need a water pressure gauge? Cant I just watch the temperature?

Is there any way to mod the exhaust to fix this? Theres no way I will be able to raise the motor enough to keep it out of the water all the time.

 

[MH Hawker]

Mecs love to run rich, while no expert by any means i would open the mixture screws to the rich side a bit at a time, what your describing is lean until it crosses over to the high speed jets.

 

[snowbrd84]

Mecs love to run rich, while no expert by any means i would open the mixture screws to the rich side a bit at a time, what your describing is lean until it crosses over to the high speed jets.

No mixture screws on these motors, only thing you can do is adjust the floats, or rejet.

 

[Faztbullet]

Back the roller completly off throttle cam and adjust engine so it idle at 1100rpm on the hose with primary timing only forget what its supposed to set at. Then loose roller and set it with a 1/8 gap between roller and cam and lake test. Make sure the gasket is good around adapter plate as if motor is to deep covering idle relief hole exshaust will fill cowlings and cause bogg as they dont like to eat their on crap....

 

[Dukedog]

Read your post again....

Just "cleaned" carbs? Were all "new" gaskets in and on tha carb installed? They are a must do no mater how easy tha old ones come off or how good they look. Tha floats should hang just past tha bowl when upside down. 'bout 1/16"....

Don't think motor to low is cause but think its still a little low. Jack plate or not? How much offset if ya have one? Have ya tried gettin' on tha "up" trim when it acts up? Max rpm trimmed out when it does do right?

 

[snowbrd84]

Read your post again....

Just "cleaned" carbs? Were all "new" gaskets in and on tha carb installed? They are a must do no mater how easy tha old ones come off or how good they look. Tha floats should hang just past tha bowl when upside down. 'bout 1/16"....

Don't think motor to low is cause but think its still a little low. Jack plate or not? How much offset if ya have one? Have ya tried gettin' on tha "up" trim when it acts up? Max rpm trimmed out when it does do right?

All new gaskets on the last cleaning. I set the floats dead even, so maybe they are a little low. When you say 1/16th below, are we talking about the lowest part of the carb float? It has a stepped surface if you know what I mean. The picture in my manual is black/white and so grainy its worthless... Could not find a single picture actually showing how the carb float would look if properly set. When I pump up the primer, it builds pressure and then holds, so I dont think the gaskets are leaking.

One thing with the carbs, I was looking at an exploded diagram yesterday and I did not realize there were jets in the cavities on the top face of the carb between the two chambers. Complete oversight on my part, I sprayed tons of carb cleaner through those ports, but did not know they were jets/removable. So I will be removing and cleaning those jets this weekend to make sure.

No jack plate, my bayliner has the built in hull swim platforms on each side of the motor, so if I put a jackplate on, gonna be a bit of work to get steering cable and the steering arm able to work. Would have to drill a new hole to move the "pocket" for the steering arm to slide into... Reading through a lot of other forums, I am seeing more and more on the exhaust ports being a real problem if they are submerged.

I honestly don't know at this point if I have tried trimming up as a solution since I was under the impression that the carbs need to be level. I think I have tried it every which way though... Now possibly, if the floats are set too high, trimming up past level would close them too early right? Thus maybe if they are set a bit lower, they would allow more fuel into the bowl when trimmed up and let the motor get going...

I called the marina and they are going to raise the motor up a couple inches and I will try it out this weekend.

 

[snowbrd84]

Just got a call back from the marina where I store the boat on the trailer, they want $180 just to raise the outboard a couple holes. A little disappointing, its less than an hours work with the right equipment. Looks like I'll be looking for a strong tree branch to hook up the come-a-long and raise it myself this weekend.

 

[SkiDad]

Hoping that fixes your problem! i think there are easier ways to raise the engine with a block of wood and tipping the trailer back with engine level- so I've heard (haven't tried myself)

 

[Dukedog]

There is little more involved without a jack plate. Unless your very lucky tha sealant around tha bolts will be disturbed. Bolts and transom holes will need ta be cleaned and new sealant used inside, outside and on tha bolts.......

When upside down, level you should have about 1/16" of tha floats visible all tha way around......

 

[Chris1956]

Gee, I use the header of my garage door and a cable hoist to lift my Mercs.

 

[Dashunde]

This may be of no help and I know very little about outboards in general... that said, I put my Gramps 1985 Champion/200 Black Max back into the water after it sat for 4+ years (installed new water pump & stats tho). It ran great.. better and better as it moved off the old fuel and onto new.
But after idling around a cove for awhile - always a little rough and it fogs for skeeters - I left the cove and got on it... it bogged and died about 30 seconds later.
I thought it was all loaded up, but its wasn't hitting a lick and there wasn't much smoke at all before it died..
So I went back and squeezed the bulb... it was soft and mushy after running a 1/2 hour or so (odd?) - I pumped it up and it fired right up. (Lucky me eh?)
I have no idea why it did that, but glad it hasn't since, 10 or so gallons later so far so good.

You said your looking for weird simple things... bogg it out and see if your bulb goes flat on wot?

Might have a fuel pickup issue with the heavier motor, plus a few people on board??

 

[snowbrd84]

20 bucks in 2x4s and a come-a-long, built an a-from and was able to lift the engine up to the last holes. raised it about 3.5 inches and the AV is a little above the bottom of the hull. The prop is still well below the bottom of the hull. The steering arm link is too far above the cutout in the splashwell, so I couldn't take it out to test. Will have to wait to later this week to go back out and cut a new hole to move the pocket deal so that the steering arm link can have full travel. Will update if it in fact solves the issue...

 

[snowbrd84]

It was the exhaust relief ports is what it looks like. Raised up 3 holes (all the way up) and it doesn't bogg at all, just halls ass... But, and there's always a but right, its too high. Prop is coming out of the water in turns and waves. I have to pretty much tuck it under once I get into any chop... Going to have to either lower it back down a bit, or maybe a jack plate? I am wondering if I can lower it and maybe drill some holes higher in the exhaust, I dunno. Im glad its not the motor itself.

 

[Chris1956]

There should be a happy medium you can find. If your boat is a deep vee hull, with the same deadrise from bow to stern, those can be a little tricky. Those hulls are not common anymore. If your hull flattens a bit at the transom, it is more conventional and it should be easy to set the correct motor height.

 

[SkiDad]

That is great news! I bet 1 hole down will be the ticket? Did you note how much the relief holes were above the water when sitting in the water ?

 

[snowbrd84]

That is great news! I bet 1 hole down will be the ticket? Did you note how much the relief holes were above the water when sitting in the water ?

Im going to try one hole down next weekend. They are about 2 inches above the water now. But that is just with 2 people and half tank of gas. I am wondering if I can drill some holes above the relief ports. It would probably make it a little noisier, but I'd rather have the noise then an engine that boggs out on take off every time.