89 Mercury 80 HP Idle (SEE VIDEO)

[JGra]

I just picked up this mercury 80 HP motor for a boat project I am finishing. I am new to the bigger 2 strokes. The carbs were rebuilt and cleaned. I adjusted the carbs the best I can on the hose. I took a video of the idle and am looking for feedback to see if I am close. I know it might be hard to tell from a video. The motor is a 1989 80 HP 3 CYL Mercury with oil injection.

http://www.youtube.com/watch?v=5xyPv7-eDlk

 

[Really Old Guy]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

I watched for about 30 seconds. Sounds good,considering it's age and
not in water. Good find!

 

[coolguy147]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

why do motors do that? they dont have a consistent idle. putt putt putt putttttt put put pu pu pu putt putt putt.

i have like ocd on these things!

 

[JGra]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

I had an old merc 200 20 HP tiller and it idled the same way but ran great on top end. These bigger 2 strokes are a bit new to me. Does any one have any ideas of what gauges I can and should install.

 

[JGra]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

Well after some long hours and days and alot of dirty looks and comments from the wife I put the boat in the water today for the first time. I still have a little bit to do in the fuel tank area but I wanted to make sure I did not have any leaks. I just used a portable tank installed today. Everything I think went very well. The 80 HP Mercury pushed the boat well. I estimate speed around 30-35mph. Dont have a speedo in it yet. Boat seems to struggle a tad to get on plane but once there it runs well. I am a new to the bigger boats and am still trying to figure out the trim settings. Should I take off with moter trimmed up or down. Ran up and down the canel a few times and decided to call it a day. I still do not have it registered and did not want to take a chance running into DNR. Getting it on the trailer was a bit differant than my jon boat. I think I had to much of the trailer in the water and struggled keeping it centered but will try some other stuff next time out. The really only issue I had was when in reverse It would jump out and make a rachet noise like it was not all the way engaged all the way. I am going to try and adjust the cable some and see if that helps. All in all I think it was a good outing. Rig is 95% complete and just need to finish the last 5. I added a couple if pic of my prod moment. Thanks to EVERYONE on Iboats for all there help and for putting up with all the sometimes dumb questions.

 

[emckelvy]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

She sounds good, like half of an Inline Six!!!

Nice looking boat, too.

I'd expect that an 80hp on that size boat, with a fairly shallow "vee", should take off smartly and go closer to 40. Maybe the prop is too large, what's the pitch # stamped on the prop? It'll either be visible on the body of the prop, or cast into the hub on the fwd end.

Looks like there's a lot of instruments on the dash, does the tach work? This motor should spin up to at least 5000 rpm at Wide Open Throttle. If not, you need a prop with smaller pitch.

If the motor is indeed overpropped, a smaller-pitched prop will allow the motor to rev up into its powerband, likely increasing speed (and improving holeshot).

BTW you'd trim the motor all the way down for best takeoff. Once you're underway, trim up so the hull "airs out" without porpoising.

HTH & be sure to post the results of your 2nd run...............ed

 

[JGra]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

Do not have the instruments installed yet. I am looking for a Speedo and Tach now. I also want to put a volt and water pressure gauge on her. I will check the pitch today and post what it is. With holeshot it seemed to stay up for about 5-8 seconds before it would get on plane. The motor came off a tunnel boat and like you said may be to much. There calling for rain today so the next trip will have to wait. Thanks for all the good advise. Like always this is the place to come for help.

 

[JGra]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

What what I can tell from the staping it says Quicksilver 48 16992 A40 22P. The 22 part is not stamped real well but its either a 22 or 32 but I dought it is 32. Is this too much prop?

 

[bryanwess2000]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

I think thats probably too much prop for that boat but you'll be able to
tell better when you get your tach my guess is you'll end up needing
a 19p prop as this is what I usually see on 75-90hp merc motors.

 

[JGra]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

Is there that much differance in the prop (19-22). I ask because I dont know anything about props. I WOT I dont think I was about 3800-4200 but will know for sure when I get the tach installed.

 

[Moody Blue]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

Nice looking setup. Agreed that the 22" pitch is too much for that boat. I'm running a 17" pitch on my 80hp pushing a older heavy 16ft deep V hull and I get 5200 at WOT with just me in the boat. Hole shot is fantastic and top speed about 30-32mph.

You boat "looks" lighter so would try the 19" pitch as a start. You should be able to get onto plane in 2-3 seconds. Your top speed of course will drop a few mph but it's important to run the motor in its proper rpm range.

The general rule of thumb is that each 1" change in prop pitch results in a 200 rpm change. So by changing from a 22 to 19 prop the rpm should increase by about 600rpm.

 

[JGra]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

Thanks for the advise. I think I will first install the speedo and Tach get some firm numbers. That way I will know what changes the prop makes. Might be able to find someone who want to trade. Its a Quicksilver Lazer II SS prop. It should be worth something

 

[JGra]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

Question about a Tach, is there any special tach needed for this motor or will any marine tach work. It is a 3 cly mercury 80 HP. There is a pigtail coming out of the control box. Is this where the tack would hook to or do I need to run it to somewhere on the engine.

 

[emckelvy]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

Most any marine tach sold nowadays, meant for an outboard, should work. Your motor has a 12-pole alternator and the tach takes signals from the output of the stator windings to the rectifier. Most tachs will have adjustable settings for different-pole outputs, you just adjust for 12p and you're good to go.

The pigtail is likely a source of tach output, of course it'd be handy to have a wiring diagram, in order to verify which wires do what. Typically a grey or tan wire is your tach signal, any other colors are ground (black) and +12V to the tach (usually a white wire).

Perhaps one of the other Guru's has a wiring diag for this motor/control box to post.

And yeah, 22p is way to much for this motor to carry except on a light, fast boat. I'd try a 19p and see if that gets you in the ballpark. It's one of the most common pitch sizes so you should be able to find one readily. Check the boat ads in your local Craigslist www.craigslist.org and I bet you'll find one.

HTH..........ed

 

[JGra]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

On the prop, I have been looking for some used ones. What do I look for? I see a lot of the add say 14 ? x 19, 13.75x21, 13x21 ect. What do I need to look for. From what everyone says I need to try and go to a 19 pitch prop which I know is the second part of the number. How do I know what the first part should be. The number on the old prop is (48 16992 A40 22P). Thanks

 

[emckelvy]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

13x19 or 13x17 would be common sizes. Anything larger than 13.5" dia probably isn't going to fit an Inline, and your motor isn't gonna want to swing that large of diameter prop anyway. If I recall nothing 14" dia and larger will even clear on an Inline gearcase.

V6 and Mercruiser props have a larger-diameter body as well, and won't fit an Inline gearcase, although the propshaft splines are the same. The difference is obvious if you've got an outboard and V6 or I/O prop side-by-side.

So the big question to ask when you're looking is does it fit an outboard.

You might try looking up props at the iBoats store, there should be a number of examples which will give you an idea of what you're looking for.

G'luck.......ed

 

[JGra]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

Thanks a bunch ED, as always this is the place to come for advise.

 

[JGra]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

My neighbor has an old merc 800 sitting around in his garage. I think the motor is a 1978 model (serial # 500922). The prop he has on there has the number 48-77344A4 17P which from what I can tell is a 13x17P prop. Would this fit my 89 mercury 80 HP and would it be worth a try and also is 17 to small. I have a 13 1/2x22p on there now. Boat seems to struggle to get on plane and from what everyone says that 22P is too much. Should I not bother and just try to find a 19P prop. Again thaks in advance for everyones help.

 

[Moody Blue]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

As I mentioned earlier, I run a 17" pitch on my 80hp on a 16ft deep V. I find it a good match with 5200 WOT and great hole shot.

Every setup is different and the only way you will know which prop is right for you is to try it. You will notice a dramatic hole shot improvement but watch the WOT rpms until you have a tach hooked up.

 

[emckelvy]

Re: 89 Mercury 80 HP Idle (SEE VIDEO)

Yes, it'll fit. Just make sure that if there are any separate thrust hubs that go with the prop, you use all of them. Some props use a different stack-up of thrust hubs etc but as long as you take the whole mess off your neighbor's motor and put it all on yours, it'll work fine. You'll know right away if there's any diff between his setup and yours.

Just like M.B. said, try it out; there's nothing to lose and at least then you'll have a much better idea of what you need without having to fork out a bunch of $$ first.

Let us know how the prop works out........ed