1985 Mercury Black Max 150hp oil injected

[librancali]

Hi all,
Ok, just replaced the stator. Took the boat out today and hesitated a little when I accelerated, but finally ran great. After about 20 minutes at high speed, engine began to hesitate. I cleaned out carbs with gumout. I noticed the oil tank in the boat had a leak (not the reserve under the cowling). Would this cause the engine to hesitate with a bad seal? A friend in the boat began to hold the cap with the quick release and the engine started working fine.
Should I buy another cap for the oil tank or could there be another problem. Does this engine have a fuel filter?
Ready to camp for a week and would love to get engine working right.

Thanks in advance!

 

[hkeiner]

Re: 1985 Mercury Black Max 150hp oil injected

My 150HP Mercury OB is a little newer than yours but I assume that the oil injection system is comparable. If it is, here are my thoughts...​

I noticed the oil tank in the boat had a leak (not the reserve under the cowling). Would this cause the engine to hesitate with a bad seal?

A leak in the remote oil tank will cause the oil from the remote tank to not reach the reserve tank under the cowl, due to insufficient pressure in the remote tank. If the oil level in the reserve tank goes down, a sensor in the reserve tank will cause an oil warning to sound. It is my understanding that a low oil level in the reserve tank would not cause hesitation in the motor, particularly if the low oil warning alarm has not yet sounded. I never had a leak myself so I don't have actual experience with such a leak. The leak in the remote oil tank should be repaired, however, even if it not the cause of your hesitation.​

A friend in the boat began to hold the cap with the quick release and the engine started working fine.​

I don't know what the "cap with quick release" is but seems like you are on to something there...​

I cleaned out carbs with gumout.​

I am not sure how you did this but if you merely sprayed it into the carb throat while the motor is running, it would do nothing to help hesitation problem and is bad for cylinder lubrication. If you want to try cleaning the carbs internals with a solvent, try using Sea Foam mixed in with your fuel. My preferred method is to mix one can of Sea Foam with 2 gallons of fuel into a 3 gallon remote tank and alternate running the motor at idle and turning the motor off for 15 minute periods. Kind of like a decarb procedure. Better yet is to remove the carbs from the motor, dismantle, and clean the parts properly by soaking them in carb cleaner.​

 

[librancali]

Re: 1985 Mercury Black Max 150hp oil injected

Thank you! I agree with you. I guess what I was told now is maybe the wiring harness from the coils to the switch box, or even the switch box needs to be replaced.
I'm drawing straws now with the troubleshooting.

 

[hkeiner]

Re: 1985 Mercury Black Max 150hp oil injected

It is my experience that solving a problem by replacing parts on a hunch (even good educated hunches) can be a frustrating and expensive way to go. This is true especially for ignition system problems as some of these parts can be expensive. The Mercury shop manual contains many troubleshooting tests for the ignition system. You can also get some tips in the FAQ section of this forum. You just need to get an ohmmeter and DVA meter to perform most of the tests. Ohmmeters are cheap. A DVA meter, although more expensive, can be a good investment if it helps you avoid replacing good components unnecessarily. ​

Keep an eye out for a used DVA meter on eBay. I bought mine on ebay last fall for for pretty cheap. I just checked eBay and there is a used Mercury/ Quicksilver DVA meter on eBay right now under the title "Mercury Marine / Quicksilver DVA meter - USED" for $55 plus shipping. I understand one can also use a "DVA adaptor" that works with a regular volt meter, but I have no experience with them. ​