7.5 Merc Outboard,,overheating?

Quick Draw · 04-24-2006, 09:54 AM

Having motor trouble. Changed gas/oil mixture thinking that I had bad gas.

Motor runs well for about 5 min. then dies and difficult to restart. Seems like overheating, with smoke coming from motor. Ran 5 mins on river and died. Couldn't get going again and had to row back. After gas/oil change, took it to Hagg yesterday (safer place to test motor) and basically same thing.

Help or feedback appreciated.

GSD · 04-24-2006, 10:02 AM

did you have any water coming out of the output hose?
Intake screen plugged?
If not, you will probably need a new impeller.

Wouldn't run it again until you resolve the problem.

Quick Draw · 04-24-2006, 10:06 AM

I don't remember seeing H2O coming out from anywhere?

Orca · 04-24-2006, 10:32 AM

Every outboard should have a tell-tail. At or near the base of the cover one side or the other at the back. Water is ejected here so that you can tell if the water pump is working and not blocked.

Hook it up to the ear muffs at home, turn on the water, start it, and if no water exits the tell-tail (or you don't have decent flow), then your water pump is shot, water intake is blocked, or water passages are blocked.

Could be the water pump impeller just gave up the ghost, or the engine was started without water and the impeller burned up. Put in a new impeller, and you will likely be good to go

Quick Draw · 04-24-2006, 10:50 AM

That's good info Thanks. What do you think it'd cost for new impeller or H2o pump if that's the case?

GSD · 04-24-2006, 11:12 AM

If your Merc output hose is like Honda's, there are times when I've had muddobbers crawl up inside and creat a blockage. If you can take the hose off and try to blow through it to see if it is blocked. If blocked, take a wire and run it through to clear the blockage.

William

Orca · 04-24-2006, 11:19 AM

$25 bucks or less I would guess. Water pump kit at ebasicpower for a 7.5 merc is $16 0r $12 (depending on model) + shipping. Local marine dealer maybe $18 - $25.

GSD · 04-24-2006, 11:25 AM

I'm not sure if your 7.5 Merc has a thermostat. That might be another thing to check. If you have a owners manual it should tell you.

night stocker · 04-24-2006, 06:21 PM

Those 7 1/2 Mercs are notorious for short lived water pumps,impellers.I know. I used to have one.Smoked all the time bad,and many good mechanics looked and worked on it.Mine was the biggest *** I have ever owned. Ruined many fishing trips with the water pump-impeller issue.Traded it in for a Honda, and much happier.Did smoke come out of the pee hole? If so,the pick-up tube that draws water to the pump has had a major meltdown.$$$$$ to have it all done at the dealer.

Sorry for the bad news.

Quick Draw · 04-26-2006, 07:21 AM

Thanks for everyone's response. I have conceded that the issue is not one that I'll take on myself. I took the motor to R & M Marine in Tualatin. Should have initial discovery of issue done today. I'll post results and outcome.

Whiteish smoke came from top of motor not from pee hole...no thermostat that I know of...motor is 1981.

Thanks again.

Quick Draw · 05-09-2006, 06:12 AM

Many of you were right on. Good job. It was a very worn out impeller and H2o pump was bad also. New spark plugs, oil, lube and some tuning has me running well. R & M Marine in Tualatin, did the work pretty quick and motor runs better now.

Note to self: The H2O intake is at the bottom of the motor not the sides. So the earmuff's will not work. Oh, so that have been what burned the impeller in the drive way.

Lesson learned.