35HP mercury outboard won't start, new to boating

sngehl01

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Jan 19, 2011
Messages
10
Ok guys, new to the forums and about equally new to boating. I've fished my whole life, and finally have a boat of my own.

Bought the boat knowing it has motor problems. Got a great deal, so that didn't matter.

The motor is a 35 HP, serial # 6491xxx, which dates it as a 1984 I believe.

Anyway, when I go to start it, it cranks, and cranks, and cranks, but won't start! It's almost like the starter doesn't have enough juice, or the battery is dying. The battery is fine, and I think the starter is too, but it's possible it's not. It sounds like when I go to start my car and the battery barely has enough juice to start it. The difference with my boat is is that it will turn over and turn over, but never fire up. The spark plugs have excellent spark. When the spark plugs are out (and the key is turned), it spins much faster and free-er.

When try to turn the top by hand, it is VERY TIGHT, almost immoveable. My 3 buddies motors (some mercury, some evinrude) spin by hand pretty easily (all between 25 and 40 HP).

Where do I start trying to figure out what is wrong? I am halfway inclined to think the head is warped or something, or the piston is swollen or the piston rod is bent, since it's so tight. The motor has around 115 pounds of compression on it, is this normal?

Just trying to figure out where to start and what to do. Thanks guys in advance for all the help!
 

SparkieBoat

Captain
Joined
Aug 17, 2009
Messages
3,643
Re: 35HP mercury outboard won't start, new to boating

sounds like you could have some serious engine problems there..if it is noticeably harder to spin than other motors..could be someone forgot to put oil in the gas and damaged the crank..or bearings...how long has the motor been sitting?
 

sngehl01

Cadet
Joined
Jan 19, 2011
Messages
10
Re: 35HP mercury outboard won't start, new to boating

sounds like you could have some serious engine problems there..if it is noticeably harder to spin than other motors..could be someone forgot to put oil in the gas and damaged the crank..or bearings...how long has the motor been sitting?

since last spring (2010). i'm betting this is the problem, mainly because it seems like I was told this may have happened.

I figured there was something semi major wrong. how do I go about getting it fixed, and what am i looking at spending? thanks a lot
 

gejandsons

Petty Officer 2nd Class
Joined
Sep 11, 2003
Messages
134
Re: 35HP mercury outboard won't start, new to boating

My 35 had problems..it had no fire on the upper cylinder..it would turn over fast then slow like the battery was really low... turned out to be the switch box....


if both plugs are firing & it spins easily with the plugs out, it sounds like a lack of fuel..if the engine has good compression expect it to be hard to turn..if it turns easily with the plugs out it is hardly internal problems in my opinion.
 

SparkieBoat

Captain
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Aug 17, 2009
Messages
3,643
Re: 35HP mercury outboard won't start, new to boating

i can usually pick up a good running 80s model 30-40 HP motor for around $700 sometimes less..keep your old one for parts
 

sngehl01

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Joined
Jan 19, 2011
Messages
10
Re: 35HP mercury outboard won't start, new to boating

i can usually pick up a good running 80s model 30-40 HP motor for around $700 sometimes less..keep your old one for parts

so you wouldn't recommend trying to get it fixed?

thanks gej i'll try that!

if anyone else has anything else to add i would greatly appreciate it
 

sngehl01

Cadet
Joined
Jan 19, 2011
Messages
10
Re: 35HP mercury outboard won't start, new to boating

it doesn't show a price. is the one i have not worth fixing, should i start looking for another? plus, that's an awful long way to drive, lol.

anyone else have any other input on what to check on this?
 

gejandsons

Petty Officer 2nd Class
Joined
Sep 11, 2003
Messages
134
Re: 35HP mercury outboard won't start, new to boating

the louisianasportsman.com link is simply a way of you getting some prices & passing some time....I'm not suggesting buying another motor..you need to trouble shoot this one. There are many people on here with high expertise levels that can guide you through the trouble shooting if you are the least bit mechanically inclined & are patient. Good luck on your project.
 

roguemercury

Recruit
Joined
Jan 20, 2011
Messages
4
Re: 35HP mercury outboard won't start, new to boating

I am having the same problem with a 9.9hp merc.
 

SparkieBoat

Captain
Joined
Aug 17, 2009
Messages
3,643
Re: 35HP mercury outboard won't start, new to boating

I would not recommend you trying to rebuild your motor yourself unless you just want to do it to learn how..but your cheapest way out is to get a good used motor...or you could take yours to a good mechanic and let them take a look at it and give you some prices to fix..my guess is it will be in the $1500 range. but if they are good and do it right you will have a good reliable motor.
 

sngehl01

Cadet
Joined
Jan 19, 2011
Messages
10
Re: 35HP mercury outboard won't start, new to boating

the louisianasportsman.com link is simply a way of you getting some prices & passing some time....I'm not suggesting buying another motor..you need to trouble shoot this one. There are many people on here with high expertise levels that can guide you through the trouble shooting if you are the least bit mechanically inclined & are patient. Good luck on your project.

ok, I understand. Thanks!

I would not recommend you trying to rebuild your motor yourself unless you just want to do it to learn how..but your cheapest way out is to get a good used motor...or you could take yours to a good mechanic and let them take a look at it and give you some prices to fix..my guess is it will be in the $1500 range. but if they are good and do it right you will have a good reliable motor.

wow, pricey! i want to know how to do it, and i'm not looking for the cheapest way out necessarily. maybe i'll just run it to a mechanic and see what he thinks.

thanks guys. if anyone else has anymore input, please post! thanks!
 

sngehl01

Cadet
Joined
Jan 19, 2011
Messages
10
Re: 35HP mercury outboard won't start, new to boating

Alright boys, got some more information for us! I appreciate all the help so far.

With the spark plugs out, I still can not get the motor to turn by hand. I can with a wrench, but not by hand. There is definitely a rubbing/creek sound at one point during the stroke. It would ALMOST start this morning when shooting some starting fluid it in, but it just wouldn't all the way go. Does any of this info help at all? Thanks!
 
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