Lovin' the new boat, ? about speed and elevation

[logsmith]

Hello all! Rank Newbie here. I do have a fair amount of boating experience but just aquired first powerboat. It turns out running your friends boats and owning one is a lot different. It is a 1980 Baja Tri-16 with (as it turns out after researching serial numbers on this site and maxrules.com,which I found through this site!) a 1979 Mercury 115 (SN 5505064). The family has had a blast on it.
I have read some posts here that say that 30 mph is too slow for this type of setup. I am running at about 7000 ft elevation and can get about 32-33 riding solo with the tilt adjusted a bit. I DO have a few issues with starting and a bit of initial bogging-poor idling and will work on some of the tips from other threads,not too worried about that yet as it does seem to warm up and run strong. The boat planes out nicely and will stay on plane down to about 18 mph. I am just curious if I should be getting more speed out of it even at this elevation.
Also curious about good manuals and high octane fuel.
I am in Steamboat Springs CO and there is a Mercury dealer in Denver, about 3 hours drive with the trailer on. So I do have a last hope.
Sorry for the huge post and thanks in advance for any help or answers.
Steve
ps I do run a bunch of different chainsaws and am familiar with power loss at elevation with 2 stroke. Just curious about the effect on boat motors.

 

[jerryjerry05]

Re: Lovin' the new boat, ? about speed and elevation

First do a compression test then a spark test. Starting and idle problems could be water in the fuel or the air screw need adjusting.Add a water seperating fuel filter.Or there is a lot of sludge in the carbs????
That old, buy a can of Power Tune(Mercury) or Seafoam.Follow instruction and run it thru the carbs.Add some to the fuel and let it go thru the carbs and let it set.
Does the boat have a tach? You might be running the wrong prop and not getting top RPM.
If you go to the Mercury site and key on dealer locator there might be one closer.Jerry

 

[logsmith]

Re: Lovin' the new boat, ? about speed and elevation

Thanks Jerry, Tach says about 5000-5100 at wot.I do believe the prop is right,based on what I've read so far. I've searched a bunch of hours now for many answers and get a lot of learnin' out of all the posts on various subjects even if it doesn't give me the direct answer I'm looking for, so it is still helpful. I can't seem to find out where to find the correct rpm at wot. Also, oil on the inside of the cover ( just a bit of a film and clean) and pulled some plugs to find them wet and oily. Will clean all and have to do a 'research' trip one more time this year. Compression test and spark test are on the way also. Will Google percent loss on two strokes per 1000' elevation gain.

 

[jerryjerry05]

Re: Lovin' the new boat, ? about speed and elevation

RPM should be max 5500-5600 at WOT.If you are at 5000-5100 then the prop needs to go down in pitch.From say a 19 to a 17 that will raise the rpm and get better performance and better gas economy.
The oil film is from any 2 stroke motor that is covered.The plugs are burning oil and gas and will never look like a car plug.Jerry

 

[logsmith]

Re: Lovin' the new boat, ? about speed and elevation

Thanks again Jerry. Is there a resource for info like rpm range? I will try to search for a manual for the motor. I will search the prop forum for more info on the prop. Mine does have a stainless prop but there are no visible markings on it. I'll pull it off soon for winterizing though, maybe there is some indication of pitch inside? Thanks again, Steve

 

[Paul DuLaney]

Re: Lovin' the new boat, ? about speed and elevation

logsmith, Are you using ngk plugs or are they champion? If champion try the ngk ,I had a lot better luck with ngk as far as not fowling and being able to go a longer before cleaning/replacemet.

 

[logsmith]

Re: Lovin' the new boat, ? about speed and elevation

Paul,I am running ngk. They aren't fouled,just wet and oily.They are ngk buhw,sound right?
Jerry, prop is a 13 1/4 x 17, Stainless.I will field test the rpms this weekend as it will be in the 60s and I have a nearly full tank.
Thanks to you both,Steve

All,Is it appropriate to start a new thread with a single question about elevation and my 115? I have done a lot of searching and don't want to offend by looking for a shortcut to the answers.

 

[Sea Rider]

About speed and elevation

About speed and elevation

Paul,I am running ngk. They aren't fouled,just wet and oily.They are ngk buhw,sound right?
Jerry, prop is a 13 1/4 x 17, Stainless.I will field test the rpms this weekend as it will be in the 60s and I have a nearly full tank.
Thanks to you both,Steve

All,Is it appropriate to start a new thread with a single question about elevation and my 115? I have done a lot of searching and don't want to offend by looking for a shortcut to the answers.

Seems you are bit over propped....low rpm/speed at wot.
What brand is your 2 strokes 115 engine ?

I did a bit of reserch about high altitude issues as wanted to fish trouts in lagoons located at five thousand meters high above sea level, if not mistaken an engine looses 10/12% HP power each 1,000 meters. In 5K will have lost 50/60 % of it's total power, a change for a down pitch will help a bit. According to some tech manual that have read no need to modify an engine under 1,000 metrs high, over that, will ned to change carb jets, adjust air/gas mixrure screw, change prop and put back as was before for sea 0elevation. At high elevation is useless to use high octane gasolines, normal ones will work ok.

There are interesting topics about what you are looking for, can be applied to outboards too, check: http://www.2-stroke-porting.com/altiden.htm

Happy Boating

 

[shanew]

Re: Lovin' the new boat, ? about speed and elevation

I was advised to always recommend to my customers to never jet a boat to elevation (unless the customer was like a competitive bass type guy that propped and jetted for every lake), always prop. Our two favorite local lakes are at 6000' and 6200'. I know what you are up against.

Mercury's theory is that the customer will forget the boat has been jetted, take a trip to the coast, and fry the engine.

Mercury also has a very good reference book available for purchase on selecting the correct prop. It is way informative! I would ask all of my customers to read the book from cover to cover before we would talk about purchasing a prop. The other thing I always advise my customers is to have your tach checked against an accurate shop tach (make sure your tach is in the ball park), and install a water pressure gauge! And if you can, add a hour meter (on these older engines). The service guys like to keep track of that number when they service your engine.

And last, but not least, the two best days in a boaters life - the day he buys his dream boat and the day he sells his money pit.