to rebuild or not...

baja32

Seaman
Joined
Jul 25, 2010
Messages
69
Okay so I am thinking of rebuilding my 150 hp v6 black max from 1980. It has zero compression on the number two cylinder the rest are between 120 and 130. I have noticed fuel leaks from two gasketed surfaces on the portside, more specifically from the crankcase seal area maybe from as high as the top cylinder but from the middle cylinder for sure and I also think some leaks from the base of powerhead. I am going to pull the block off and take it apart. What should I look for in terms of the block not being viable for a rebuild??? I have also noticed some oil like substance dripping from prop hub, at first I thought it was carbon but I have also seen it on days when I've tried to start the engine up and never got it to start, is that a sign that the blocks no good??
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: to rebuild or not...

The messy goo in the prop hub is simply unburned fuel washing carbon accumulation out from the exhaust, signs that this baby has needed a litle attention long before you fried #2.

The motor IS rebuildable at far less cost than replacing the powerhead, IF, you do most of the work yourself. Common sense, attention to detail, it is NOT rocket science, many have learned it to be quite simple once you understand each part and its function.

Machine work must be farmed out to a reliable machine shop capable of boring or resleeving an outboard motor.

Order an OEM Service Manual, don't waste your time or money on aftermarket books, they all lack the detail found in the Mercury Manuals.

Your goal is not to just rebuild your motor, but to determine WHY it failed, cure the cause of that failure,learn and perform the maintenance your motor needs to prevent a future failure.
 

baja32

Seaman
Joined
Jul 25, 2010
Messages
69
Re: to rebuild or not...

How should I go about determining why unburned fuel leaks out of the exhaust?? I plan on doing the rebuild myself (minus the machining of course).
And yes I also want to determine why the cylinder fried out, however it is a 30 year old motor and I have only had it since May.
 

CharlieB

Vice Admiral
Joined
Apr 10, 2007
Messages
5,617
Re: to rebuild or not...

Either before the tear down or after the rebuild you will want to
DVA test the stator, triggers and ignition module output to each coil to ensure all are up to performance standard, as well as testing spark output of each coil to ensure a bright blue arc of a minimum 7/16 inch in open air, any less may mis-fire under full compression at WOT allowing unburned fuel to pass thru the engine.

A complete carb rebuild, and fuel pump, is necessary to ensure proper fuel supply and flow at all throttle settings. A dirty jet, low float level, or weak fuel pump will allow one or more cyl's to burn lean, melting another piston.

Cooling system maintenance, rebuilding the water pump, poppet valve, and T-stats to ensure cooling, preventing any piston seizure from overheating.

Linking the carb throttles to the timing adjustment to ensure spark advance in synch'd to throttle opening, setting maximum advance at WOT.

All are critical to achieving performance and reliability from your motor.

Read the OEM Service Manual, at least twice, follow it to the letter.

Any questions, post them here, it is MUCH better to ask for more clarification than to risk damage to your motor.

Many of us have 'Been there,.......' And we are more than willing to spell it out if there is ANY misunderstanding.
 

baja32

Seaman
Joined
Jul 25, 2010
Messages
69
Re: to rebuild or not...

Yes I am going to definately rebuild the carbs and fuel pump, and replace all the cooling system components. I am also going to test the electrical components.

I have been browsing online and have found that a number of sites sell powerhead rebuild kits. I wonder if anyone knows which would be the best to purchase?

Im also going to replace the reed valves & ignition coils of the bat.
 
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