1986-1987- Mercury Black Max 150 not getting max rpm/ warning on startup/

[jhndrtxn]

1. Engine Serial Number: 0A957221
2. Year/Make/Model: 1986-1987/ Mercury/ v-150 ELPTO
3. Currtent Prop: Tempest Plus 2 14.625 x 23p
4. Current Maximum RPM: 4400
5. Idle and WOT Water Pressure Readings N/a
6. Smartcraft or Analog Instruments? analog replaced rectifier recently
7. Any Engine Mods? unkown

So this boat had been in storage for 6 1/2 years prior to me running it this past weekend still has some old fuel in the tank but I never put ethanol fuel in the tank since i bought it in 2011. Last time it had run was in 2015 the fuel line connector broke while loading at the ramp and the engine was run until it shut off.

I've been working on this motor for the last couple weeks going through it checking things over replacing worn lines/ wires. Replaced the rectifier as i had no tach one post had a short to ground. Replaced the water temp sensor on the right head for the warning alarm as it was corroded. Previously had a no name 14.25 x 22p prop no name on it thin blades but had been able to run 50-53 mph solo but had no tach to compare to current rpm. Just recently replaced starter solenoid, and starter and throttle cable on the boat

I took the boat out sat morning to do a shakedown/ little fishing. The motor was hard to start 5-10 mins of cranking before she got going. even following the "startup procedure" ever since i've owned the boat after startup the warning alarm i would get a solid Beeeeep, but once underway it would go away or would go away if i rev'ed the motor up past idle. On holeshot the motor seemed "loaded" the whole time not bogged or sluggish but just a consistant moderate rise in rpm until it reached max rpm the boat felt like it popped out of the water onto the pad. Max Rpm i saw was 4400 rpm but was running 51-52.

I still have old fuel in the tank with seafoam and stabilizer and i have been running the motor at home with muffs to do some diagnostics.
How can i test the tach to see if it is working correctly for one and what would cause the motor to not go beyond 4400 rpm or could i be looking at a stator issue

[JOE54]

no way it can run 52 mph at 4400 unless on very light boat and very large prop check setting on back of tach , replace water pump and all 3 gaskets

[SilverFox579]

I'd drain every drop of that old fuel, even if treated with stabilizer 6.5yrs ago it's stale. Refill with fresh fuel of the correct octane for that engine.

[JOE54]

^^^^^+1

[jhndrtxn]

Well it was a short lived victory must have had some crud in the bottom of the tank and some water, went out Friday and it would only stay on plane for about a 100-500 feet before it sounded like half the motor shut off an lost power. Got it home and went through it today pulled the main jet plugs out and it was full of junk and had water in it as well since I had the carbs off i decided to look at the reed valves an I've got a couple that are not seating all the way or are very lightly closed. Still has the stock reed valves so I'm going to order a set of Carson's. The fuel pump diaphragm was toast it had some give but it was pretty much hard and a couple spots where it was about to fail. Also goin to replace all the 1/4" line under the cowling as I believe those hoses may have contributed to the sediment. i also found that one of the bleeder lines was pinched under the choke plate an the bottom carb so going to replace that

Also the beeping i was hearing was the low oil level for the motor mounted tank i re-primed it and havent heard from it since, I have a new Tach coming as the one on the boat no longer has the settings for the adjustment the have worn off but i use my multimeter and got it close using hertz. Service manual is enroute with new gaskets and i will be doing the link-n-sync.

[JOE54]

inspect screen in oil tank pickup also for gelling

[jhndrtxn]

will do

[jhndrtxn]

no way it can run 52 mph at 4400 unless on very light boat and very large prop check setting on back of tach , replace water pump and all 3 gaskets

Joe are you talking a bout 19, 23, 24, 25 is the faceplate
Water pump.png

[JOE54]

yup

[jhndrtxn]

I notice alot of videos for water pump replacements only do the 2 they never do the lower pump to gear housing

[JOE54]

duely noted , i will look for them and learn about MERCURY ENGINES

[jhndrtxn]

duely noted , i will look for them and learn about MERCURY ENGINES

Not insulting your intelligence jus something I had noticed the gasket comes in the kit but you only ever see people putting in 2 gaskets. I get it your already there do the job right and replace them all

[JOE54]

too close to it to not replace it ,many failed water pump replacements are caused by not replacing this gasket that has a very weak spot on rear area and one breach in it will cause over heat and or brunt impeller ,but dont tell those videos this cause thats the of folks that we like $$$$$$$$$ we get to buy toys and food and cars and trucks and boats a nd all kinds of stuff good luck JOE

[jhndrtxn]

Thanks Joe, Waiting on New reed valves and gaskets for the carbs and such I Had water and debris in the main jets after putting fuel in the tank anything i should look for while i got it this far apart

[JOE54]

set up that long no way id put it back together without inlet needles and seats ,

[jhndrtxn]

Drained all the oil in the 3gal tank and engine mounted tank after looking at the pickup tube for the oil it was gelled up and had debris in the oil, new reeds installed waiting on gaskets and inlet needle valve/ seats, replaced plug wires and new plugs checked my poppet valve and tried to remove the rubber diaphragm to try an pull it out but couldnt get it to budge it moves in and out freely so i just left it alone. waiting on the service manual to see how to properly remove it

[JOE54]

they can sure get stuck

[jhndrtxn]

I didnt want to force it in fear of damaging it. But if it is Stuck is that all I can do is use force?

[JOE54]

yes sir most likely

[jhndrtxn]

This weekend I got the carbs cleaned/rebuilt, set the floats, replaced bleeder lines, rebuilt fuel pump, installed carbs, new lines all the way around I used tygon hose instead of regular fuel line, replaced the oil lined from engine mounted tank and oil pump. I followed the service manual on the timing link and sync. I used a 3 gal portable tank to do my first startup as I had to purge the oil line from the pump, First priming took forever once that was done I used the choke for 10 seconds turned the key on a new 1000ca battery, 31s30 from advanced auto, and the motor roared to life almost instantly. i had it on muffs i let it run for about 3-5 mins and then it started to die out and finally just quit could see that i was not getting fuel to the carbs so i started looking for restrictions in the fuel line. I found that the nylon/plastic bayonet connector with the original 90* would not let the plunger depress far enough to allow fuel to flow unrestricted. You cannot get the original cast bayonet style any more so I'm looking at different options for fuel connections but in the meantime im going to replace both connections engine and tank side to the nylon/plastic as i still had the cast female on the tank side and woke up to a half gallon of fuel in the garage due to the original connector not sealing.

Question about the oil injection line from the pump, I have a tygon 1/8th in line about 6-8inches long running from the pump between the 2nd and 3rd carb to the oil injection Tee right before the fuel pump (old style) i have my fuel line ran under the 3rd carb to the tee as i was getting interference with the fuel lines ant the throttle lever with the Roller not allowing the motor to return to idle position.
Is there a maximum length for the line as originally it was only 2-3 inches an the tee was near the oil injection pump do I need to reconfigure my lines or will the way i have it be fine