1977 MCM 120--whining at carb

[jacko137]

Four issues I'm concerned about after her first couple test drives ( 2.5 hours of driving--very little WOT; a combo of idle speed and up on a plane--small bursts of WOT) I should note, it's possible that I"m being way too anal about engine noise as this boat is new to me and I'm not much a mechanic. I'd love some expert opinion.

#1. After throttling back to idle speed after cruising for a couple minutes there is a whining--maybe a vacuum hose?--at the carb. It lasts about 40 to 60 seconds. It's very prominent. Should I be concerned?

#2. There is a rattling noise--almost sounds like a fan belt would on a car--within the block. More prominent on the port side. present at all times--more prominent after high rpms (or perhaps my neurotic mind).

#3. What temp should this motor run when fully warmed up? It reads only a hair over 100 degrees. I've put in a new sender, gauge. That can't be right, can it?

#4. Last--I checked my out drive fluid and it is still pretty clear--with good blue hue. But I had a couple very very small metal shavings on my finger afterwards. No noises from outdrive and she seems to get up good. Should I chalk it up to a 30_+ year old drive and use her, or do I pull her apart at this point?

THanks in advance for any suggestions across the board.

 

[achris]

Re: 1977 MCM 120--whining at carb

On the gear oil, the blue stuff is the 'good oil'. It's Mercury High-Performance Gear Oil and is the only oil recommended by Merc. The small quantity of metal is also normal, even with brand new drives.

Your temp should be about 140. Be aware that the gauge/senders are not degree accurate, they give an indication only. If it doesn't fluctuate too much, then I'd be happy with that....

Sounds are very difficult to diagnose by description. The noise 'like a fan belt' could be just that. I usually replace belts as soon as they start being noisy. They're cheap compared to a lost day on the water.

The 'vac' noise is too hard to call. Does it do it only under load?

Chris.........

 

[chiefalen]

Re: 1977 MCM 120--whining at carb

Beg borrow or steal a infrared gun. Confirm the temp. at 2 places on the t-stat housing.

Ok about the t-stat 140. If i remember right. You could pull it and drop it in boiling water with a thermometer and see if it opens at 140.

Make sure the vacuum steel tube is stuck good in.

Carbs do make noises if running good leave it alone.

How is the engine mounted water pump? Leaking a little? All the pulleys bolted in tight?

Alternator original? You burn one alternator belt and thats the original alternator change it.

Did you put a spare belt on around the mount and tie it to the front motor mount out of the way. If belt does goes 2 minutes you can have the spare on.

All you would need is a 1/2 wrench and a piece of pipe or long screwdriver for leverage on alt.

Excuse my long post grasshopper looks like you got that ole girl running enjoy!