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post #1 of (permalink) Old 08-20-2004, 01:11 PM Thread Starter
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O/T Old Mercury outbaod question

HEres the scoop, bought a 1955 14' Thompson wood boat on Manday witha 1961 Mercury Mark 35 (4cyl 35hp) outboard on it of unkown status other than it runs.
Monday night put boat in water, myself and two friends (about 560lbs total) and the boat went fine got on a plane and went about 30mph.
Tuesday night same thing
Wednsday night my brother in law and I wetn out and it felt like we were going slower than previously but such a small difference thought we were fighting the wind or current.
Thursday I put new plugs in it (same brand and model) and the night started of okay. I then had a friend and his wife jump in (around 475lbs total) and could not get on a plane, even thought it was at full throttle, it didn't seem to be revving very high. We played with the idle fuel mixture screws to no help. On the way back to the ramp it was at full throttle, but barely running, but can rev up fine in nuetral. When you do rev it in neutral it seems to have a miss, then cleans out.

I have not ran a compression check or anything else yet.
I am leaning towards ignition problems thinking that the points could be old and when the new plugs were installed the points are now failing when a load is applied.
Does this sound feasable? ANyone know if the early Merc's have an opening in the flywheel to view the points, or does it need to come off?
Do they make point conversion kits (like pertronix) for outboards?
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post #2 of (permalink) Old 08-20-2004, 02:26 PM
 
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Re: O/T Old Mercury outbaod question

Sounds like 2 possibilities:
1.The power pack. When the power pack goes, it will run fine in neutral, but as soon as there is a load on it it will not give out much power.

2. Propeller hub could be bad. There is a rubber hub that connects the propeller blades to the spline. Sometimes the rubber comes loose and it will just spin on the spline. If this happens the prop will not turn at all or very slowly.
Kinda like airing your tires way down and you give it a little gas, the wheel spins but the tire does not.
If it is the original prop, or an old one that has been sitting around a while, this is probably the problem.
See if you can borrow a prop from a friend or a prop service shop and try it with another prop.

Hope that gets you going.
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post #3 of (permalink) Old 08-20-2004, 02:41 PM
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Re: O/T Old Mercury outbaod question

If the prop was the problem revs would still come up, you just wouldn't go anywhere. I agree that the points would be a first place to look.
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post #4 of (permalink) Old 08-20-2004, 02:44 PM
 
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Re: O/T Old Mercury outbaod question

What do the plugs look like? Is it making a decent spark when you observe a plug removed?
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post #5 of (permalink) Old 08-20-2004, 03:49 PM Thread Starter
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Re: O/T Old Mercury outbaod question

Prop is old brass style with no rubber center.
Plugs I pulled out looked pretty good actually, burning about right and not too oily.
I just got home so I am going to pull the new plugs out and see how they look.
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post #6 of (permalink) Old 08-20-2004, 06:23 PM
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Re: O/T Old Mercury outbaod question

The water pump on those motors consists of a hub with rubber impeller blades. When they get old the blades get brittle and break off. And when that happens, the engine will toast pretty quickly. Ask how I know, and bring a six pack when you do.

Anyway, there should be a nice stream of water squirting out of the right side down low on the power head. If it's not there, or just a dribble, you might have toasted it already. Or if you're real lucky the blades are still partially there and pumping water, but not enough. Then the problem is that the motor is getting hot and losing power.

On the second motor, we had a new water pump put in every spring. A new water pump is a lot cheaper than the second motor. [img]images/graemlins/blush.gif[/img]
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post #7 of (permalink) Old 08-21-2004, 05:49 PM Thread Starter
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Re: O/T Old Mercury outbaod question

I pulled the plugs and they are all good,
Compression check gets 120 lbs on each hole
The points were pretty burnt and pitted, as well as being worn way down on the lift block so they weren't opening much if any.
Cap had about 1/3 of the side broken and pieces inside, rotor was pretty worn as well.
They are really proud of parts for old engines [img]images/graemlins/blush.gif[/img]
Water pumps out water really good.
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post #8 of (permalink) Old 08-24-2004, 10:53 AM
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Re: O/T Old Mercury outbaod question

Have you taken it out by yourself since then? A 35 hp isn't a big motor. My old boat had a 40, and one additional person was the difference between it getting on plane, or dogging in the water. Plus that was an aluminum boat, which was much less wait than a wood hull is to push through the water.
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post #9 of (permalink) Old 08-24-2004, 11:58 AM Thread Starter
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Re: O/T Old Mercury outbaod question

Yes, when I first got it it pulled three of us bigger guys on a plane easily, then it wouldn't pull two guys and a light lady up on a plane, then I dropped them off at the dock and it worked a bit better, but still wouldn't get on a plane. Parts should be here tomorrow, so after that I'll know for sure.
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post #10 of (permalink) Old 08-24-2004, 02:44 PM
 
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Re: O/T Old Mercury outbaod question

oldmercs.com

for your parts ( cheapest ive found)

I run a 1971 80hp on my striper boat.

that is good advice on the water piump impeller, it NEEDS to be replaced if you dont know how old it is ( every year is great) ever few years is ok if you always verify the water is pumping while its running.

the impeller costs about $30 and it takes an hour or 2, the hardest part is getting the shift mechanism lined back up.

those old engines did not have stainless driveshafts either, so sometimes they are nearly impossible to remove the lower unit.

Good luck!

oh yeah, look on the merc forum on iboats.com

the best info ive found out there on those old beasts.
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