Merc 60hp @ high altitude

[donrjuan]

My 60hp seems to be suffering when i throttle up (sluggish/hesitates). Question one: should this moter be able to get a 16' Skeeter on plane, cuz it won?t. Number two: it may be jetted for low altitude as the original owners had it in Arkansas but I now run it in Colorado (aprox. 4500'+), think it needs re-jeting?

I have gone through the ignition and vacuum system with a fine tooth comb and all seems to be working properly. All fuel lines have been replaced along with vacuum hoses. Carbs were gummed up when I got it but are now spotless. I am going to clean and inspect the mechanical fuel pump tomorrow.

Any advice would be greatly appreciated!

 

[CharlieB]

Re: Merc 60hp @ high altitude

4500 ft is getting up there, you MAY need to downsize jets.

First, try touching the choke as you experience any bog or hesitation to see if the additional fuel helps or not. Two strokes need the idle mixture set almost 1/4 turn out past best idle speed in gear in the water to provide the additional richness for acceleration.

I suspect that is your major cause of the bog.

Once you are able to run WOT cut it off as quick and clean as possible without a following wave swamping your boat, pull the plugs and see how rich they are burning, then decide if you need to downsize the main jets.

Have the serial # of your motor handy then go here to look up your carbs and available jetting.

http://www.mercruiserparts.com/SelectProductLine.asp

 

[rockpile]

Re: Merc 60hp @ high altitude

You will also need to change the prop to a lower pitch. I'm curious to know where in CO you are, lived and worked out there for a few years and know many dealers in the Front Range area.

 

[donrjuan]

Re: Merc 60hp @ high altitude

I did bump the choke once just for sport but is made things worse, more hesitation. I will try the clean cut next time I am out and see what results I get. I can tell you that it is rich. I pulled the plugs yesterday after an outing and they were fueled up pretty good. In fact I ran out a grabbed some more to have backup incase they foul. The carb adjustment does no excite me since there are three of them. I wanted to narrow down all other conditions before this critical step was taken.

Rockpile I had considered the prop situation based on some other posts here. I have little knowledge of props (for boats any way) and was unsure which way to go on it. BTW I live in Colorado Springs and boat in Pueblo res, John Martin res (both lower altitude) and in Eleven Mile and Skagway res (both 8000'+)

Thanks guys and keep it coming!

 

[rockpile]

Re: Merc 60hp @ high altitude

Sterling Marine at 405 W. Filmore in Co Springs.
I worked out of the Longmont and Denver locations several years ago. Every rig we got in had the stock prop returned, possibly re-jetted and all Mercruisers had gear changes. High altitude has a huge affect on performance. Before you start replacing parts at random, stop in and see them and ask for their recomendations.

Many fond memories pulling Rainbow Runners on Elevenmile for Kokanees!!

 

[donrjuan]

Re: Merc 60hp @ high altitude

So I have been looking around and am wondering if there is any adjustment I can try on the crabs before rejetting? Also once I rejet, will I have to make these adjustments any way?

 

[Karl_Childers]

Re: Merc 60hp @ high altitude

You cannot adjust it out, you must re-jet. Going from sea level to 4500+ feet will reduce your HP by about 30 percent, which makes it about a 40 HP motor if every thing else is 100 percent. Forty horsepower should still make it plane, I would think, but it would be slow as mud. Good luck

 

[Aqualift]

Re: Merc 60hp @ high altitude

I have a 1965 Merc 500 (50HP) and on my 14ft fiberglass Glastron, I hit 28 MPH. It gets on plane very fast and I run at a reservoir that is located at approx 7300 feet. Next time that I have the carbs apart, I'll find out what the jet size is. I'm curious to what, if any changes were made to the jets over the years by previous owners.

I have the idle mixture screws set to 1 1/8 turns out.

 

[donrjuan]

Re: Merc 60hp @ high altitude

That would be great Aqua. I am going to check mine tomorrow to see what size is in there. I contacted the original owner and he tells me it was originaly tuned to high altitude then taken to Arkansas but never retuned. So in theory it is properly tuned to the elevation! I am getting just a bit stumped on this one. Any help would be great.

 

[donrjuan]

Re: Merc 60hp @ high altitude

Did you know that you can not find a set of wire feeler gauges any where! Every one has flat feeler gauges for gaping plugs and what not but not the kind that is used to see what 1000ths' hole is in your jets! Well any way, I went to the boat store here on Fillmore Ave and the guy there tells me that changing main jets is nonsense. Said it was a wives tail and that any performance issues were caused by a combination of prop pitch and idle mixture. Now my Chiltons repair manual tells me that the proper jet is the key to good performance but I guess this guy missed that chapter. He also gets red in the face when I tell him that there are no vacuum hoses running from each carb back to the block. He tells me that some @$@ hole must have removed them and that is the problem. Well there never were any hoses. The book never refers to them and there is no open port to insert them. He ended our conversation by telling me I was sure to wreck my moter and that I should just bring it up to him for service. I think I am going to run it by just long enough to show him the phantom vacuum hose Any how I just wanted to blow off a bit of steam before I start turning wrenches.

 

[87TX17]

Re: Merc 60hp @ high altitude

I had the same type of dealings with that place. Only I got them from the female that works the register/parts counter from time to time. Thats why I started sourcing parts online. The guy down at Outboard Marine Ski and ATV in Pueblo is a real good guy. Bob Sanchez. But the prices are not so great. But the customer satisfaction is way better. And they may be able to point you in the proper direction for the gauges. Their number is, 719-547-4600... dont forget the 719 its a Pueblo number. Hope they can help you out.

 

[sschefer]

Re: Merc 60hp @ high altitude

Are you running premium or regular gas. Try running regular. With less octane and less oxygen it will burn at the nearly the same rate as premium at sea level. Higer octane = slower burn rate providing power throughout the stroke. At high altitude it results in unburnt fuel at the end of the stroke causing an over rich condition.

Two cycles and high altitude take special care. Drop an inch in pitch, get a high altitude gear case and re-jet if you're going to make it a high altitude engine. Better yet, trade it in on a new E-Tech and forget about it.

 

[donrjuan]

Re: Merc 60hp @ high altitude

It?s alive! I tuned the idle mixture using a shop tach and now it is running pretty good. I am not going to re-jet it due to the variation in altitude between the lakes I will be fishing (4000?-8500?). I am looking at new props now. Thanks to those who contributed the great advice!

 

[rockpile]

Re: Merc 60hp @ high altitude

Good to hear! BTW, I found out the place I sent you is not run by my former employer anymore and from what I heard, the new guy is that way to most who have not bought a boat from him. I'm very sorry that I sent you in there and that you had a bad experience.

 

[sschefer]

Re: Merc 60hp @ high altitude

I've been running my boat with 100 1991 Mariner at 5200 ft for the past week. Runs great when I first put it in the water early in the morning but runs lousy later in the day. The mechanic here said the only sure cure is to rejet, he does it for all the permanent residents.

It seems that during the wee hours of the morning when the boat is out of the water, the fuel cools to the outside temp of 35-40 degrees and the air is dense. When the boat is first put in the water, it runs great. Later in the day, the lake water warms the fuel to 70 degrees and the warmer outside air is less dense so the mixture no longer burns properly.

 

[donrjuan]

Re: Merc 60hp @ high altitude

Not sure man. I am happy with mine now and since I am going to be running it from relly high to kinda high altitude I decided to just go with it. No rejetting and just some seriously fine tunning (3 carbs + 6 beers = 4 hours tinkering ). I would say however, be sure you are somewhat aware of the carb timing process when undertaking jets or simply fine tunning. Good luck to any one who is in the same... well boat.