LOSS OF POWER? 1979 MERC INLINE 150HP

[JJ JOHNSON]

Haven't run this boat in about 2 years. Over the last 3 fishing trips I've had a somewhat gradual loss of power. 1st trip I was running ok at full speed & motor quit. Started back up immediatly but it took 30 to 60 seconds at full throttle to open back up & plane out. The 2nd trip I had trouble getting it to open up at full throttle. Would take 1 to 2 minutes. By the end of 3rd (and last) trip it would only turn around 2,000 to 2,000rpm.Tried pumping the bulb and it was firm and caused no change in speed.Pressed choke and the motor died down even more.Could it be bad/old gas?,<br />Points?,fuel filter? or something really bad ? Still cranks up no problem. Help

 

[Walter]

Re: LOSS OF POWER? 1979 MERC INLINE 150HP

Pull each spark plug and inspect. You may have a burned piston. That's about the worse scenario I can think of. If that's ok, then go for the more obvious things. You ask if the problem could be old gas. Well, YOU tell us! Did you use fresh gas or 2 year old gas? If the later...well, shame on you!<br /><br /><br />Walt

 

[JJ JOHNSON]

Re: LOSS OF POWER? 1979 MERC INLINE 150HP

I added fresh gas to 2 year old gas. "It's<br />hard to be a retard." I assumed this would be ok but have been told today that that is like mixing gas & varnish. Is that possibly the problem ? If I pull the plugs, how can I tell a burned piston? Thanks for your help.<br />JJ

 

[what200]

Re: LOSS OF POWER? 1979 MERC INLINE 150HP

I think JJ already found his problem but I've been told many times that the inlines are very sensitive to fuel quality. Bad gas or even low octane gas will cause an inline to knock or detonate. I have found a link to a very detailed explanation of fuel, octane, and effects of such (I will post it if someone wants me to). It pretty much says that you can mix fresh gas with old gas (like 6 months) to "cut down" the old the stuff and it is runable. However, it must be run immediately as the fresh gas will quickly start to varnish itself. Two year old gas is not really gasoline anymore. If it was me I would run 92-93 octane in an inline.

 

[Lark40]

Re: LOSS OF POWER? 1979 MERC INLINE 150HP

I'm a little confused by your description of the engine. I had a 150 hp Mercury 1500, inline six made in 1977. That was the last year for the inline six. They went to V-6 in 1978. What do you actually have?

 

[steve forsythe]

Re: LOSS OF POWER? 1979 MERC INLINE 150HP

Probably not the same as mine but your symtoms are EXACTLY the same as my 200 merc that ended up with a broken ring. Maybe do a compression test, a ring could have gotten stuck when not in use and then broke.

 

[JJ JOHNSON]

Re: LOSS OF POWER? 1979 MERC INLINE 150HP

I just did a compression test & I have 5 cylinders with 120 to 126 psi. But the #3<br />cylinder only has 28psi. Also,the spark plug from #3 had a few tiny aluminum looking pieces on it. A local mechanic said the whole powerhead would have to be reworked,<br />new piston on #3, etc... $1,000 parts & labor<br />This motor is an inline-6, though I'm not positive on the year. Do I spend $1,000 on a motor this old and keep it? or sell it? Or try to sell the whole rig as is. Is this old motor worth it? I don't want to throw good money after bad. What would you do?

 

[Lark40]

Re: LOSS OF POWER? 1979 MERC INLINE 150HP

If I were you, I would have it rebuilt. My 1500 was easy to work on, powerful, and reliable. Being a pre-computer model also has its benefits.<br /><br />You can't touch another replacement engine's cost for the $1,000 expense to fix yours.

 

[what200]

Re: LOSS OF POWER? 1979 MERC INLINE 150HP

I would agree with Lark that 77 was the last year of the 1500. Continued to make 140 until it was rerated at 115 at prop shaft in early 80's. If you have the serial sommebody could probably tell you what you got.<br />JJ where do you live in Alabama? I might have an inline powerhead for you.

 

[JJ JOHNSON]

Re: LOSS OF POWER? 1979 MERC INLINE 150HP

I live in Shelby,Al (near Columbiana)a couple of miles from Lay Lake. I work in Bessemer. What would your powerhead cost ?<br />Is it ready to go? <br />Thanks for all the help and responses

 

[what200]

Re: LOSS OF POWER? 1979 MERC INLINE 150HP

JJ- Send me an email- watfor20@aol.com<br /><br />-Hunter