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Author Topic:   Repower 13' for high elevations or buy another boat?
Sport 13 posted 12-06-2003 10:36 PM ET (US)   Profile for Sport 13   Send Email to Sport 13  
I am new to this forum, but have been monitoring it for years. This web site is absolutely fantastic and contains a lot of great information. I have searched as many postings as possible about re-powering a 13' Whaler, but I have a peculiar situation: very high elevation boating. I have a 1983 Sport 13 with a 1983 Johnson 35 HP motor. I use the boat primarily on mountain lakes here in Colorado, some as high as 10,000 ft. I am running a 11 1/4 x 7 prop (the lowest pitch I am aware of for this motor), and the boat is a dog with anything more than two adults on board. I know it's an elevation problem because the boat flies at sea level with the same load and a higher pitched prop. My dilemma is this - would it be worth the relatively large expense of re-powering with a newer (post-2000) 40 HP outboard, or should I just get a bigger boat with more power? I don't know if the marginal difference in power from a modern 40 HP would be enough to overcome the high elevations where I boat. I also tend to carry my 5-year-old son and our dogs on board, so the load can get fairly heavy at times. I love the 13 and would like to make it work, but am ready to move on if need be. If I were to get a bigger boat, I would probably buy an older Montauk or Nauset with 90 HP. I'll keep the 13 for my son. Any thoughts about running at high elevations would be great. Thanks.


Jerry Townsend posted 12-06-2003 11:10 PM ET (US)     Profile for Jerry Townsend  Send Email to Jerry Townsend     
Brian - the solution to your problem is, most probably, carburetor jets. Ask your local dealer what jets you should have in your carburetor - and have him replace them or replace them yourself. ---- Jerry/Idaho
whalersman posted 12-07-2003 12:37 AM ET (US)     Profile for whalersman  Send Email to whalersman     

I agree with Jerry... Check with your dealer... There is a high altitude kit (anything above 5,000 feet) for the older motors which involes several jets in the carbs. Of course if you are going to be using the boat below the altitudes, you will have to change the jets back again..

The second alternative would be to buy a newer computer controlled engine that adjusts for altitude automatically but that of course would be much more expensive...

Joe/Mountain Ranges of Upstate California (3,000 to 6,000 feet and then down to Sea Level)

Bigshot posted 12-08-2003 02:46 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Another guy here has the same setup in high altitudes but runs an 11" where a 13" is ideal for most sea level people. A 7" is ridiculous and sommething is wrong. If a load is heavy, get a bigger boat, store that for another 5-7 years and repower then.
kglinz posted 12-08-2003 03:19 PM ET (US)     Profile for kglinz  Send Email to kglinz     
Though changing jets may make some improvement, the problem is mostly an air density problem. Prop changes are the only answer. 4% per thousand feet of altitude lose on a naturally aspirated engine. Hold off until the 4 stroke Mercury X engine is out.
Tom2697 posted 12-08-2003 04:25 PM ET (US)     Profile for Tom2697  Send Email to Tom2697     
A new boat is always nice but you should be able to get your boat to perform well. As the others have mentioned, you need to change your jets. At the higher elevations, you're dumping too much fuel into the engine. But, when you return to sea level, you will run too lean unless you change them back.

If you are looking for a new engine, definitely go computer controlled and fuel injected (do 40hp's come injected?). This will adjust your mixture automatically whenever you start the motor.

Anyway, try a different prop whenever you load up that boat with weight regardless of your altitude. Adding an extra 300+ pounds to a boat with a small engine destroys your power to weight ratio and hence, how your boat performs.

Sport 13 posted 12-08-2003 05:20 PM ET (US)     Profile for Sport 13  Send Email to Sport 13     
Thanks, guys. I'll start with the jets. I also think the 7 pitch prop is ridiculous. I have an 11 x 9 prop that I will try again after the new jets. It's snowing today, but in a few days I will make the changes, put on a parka and ski goggles and give it a try. I want to get this sorted out this winter so I can either restore the 13 or start looking for deals on used Montauks before next spring.
Sal DiMercurio posted 12-08-2003 06:03 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Sport,where are you in Colorado ?
By any chance are you in the Grand Junction area ?
I'v fished the Grand Mesa lakes & not only changed the prop, but also the the plugs need to be hotter.
You wont get much improvement on any carbed engine but a DFI will work just fine.
As stated here, absolutly do "NOT" run that engine at sea level with the high altitude jets in there, because you will fry that engine in 10 minutes because she will run far to lean.
No matter what you do to your carbed engine, it's still ging to be a dog in the high country.
Your 35 hp is probable only putting out about 22 hp at best up there.
andygere posted 12-08-2003 07:12 PM ET (US)     Profile for andygere  Send Email to andygere     
If you are considering a repower, Tohatsu makes a TLDI ("clean" direct fuel injection) 40 h.p. in both 15" and 20" shaft lengths, available with power tilt and trim. It could be just the ticket to help your 13 perform up to its potential in that thin air.
Sport 13 posted 12-10-2003 04:16 PM ET (US)     Profile for Sport 13  Send Email to Sport 13     
Sal – I live in Denver and boat on Dillon, Granby, Turquoise, and other high mountain lakes. I am planning a camping trip to the Grand Mesa area next summer. Any tips regarding camping (with 22’ travel trailer) and boating spots?

I am starting to think about keeping the 13 and re-powering – too many good memories on the boat, and I love its small size. Thanks, Andy, for the Tohatsu suggestion. I contacted a local Tohatsu dealer who said that the 40 TLDI currently cannot run at this altitude. Apparently Tohatsu is working on re-mapping the electronics to make it perform better. The dealer proposed the Tohatsu 30 four stroke (although it is carbed). I have decided that I do want a four stroke, so these motors seem to be my best choices (prices include tilt/trim, gauges, remote control and installation):

Tohatsu 30 four stroke carbed– $3,894 ($4,394 - $500 trade-in); 150 lbs.

Yamaha 40 four stroke carbed – $5,719; 191 lbs.

Honda 40 four stroke carbed - $5,900; 198 lbs.

Suzuki/Johnson 40 four stroke EFI – $6,095; 243 lbs.

Mercury 40 four stroke EFI - $5,925; 216 lbs.

Evinrude 40 two stroke e-tec - $5,025; 235 lbs.

I apologize if this topic has been beaten to death on this forum, but I searched the entire performance archive in the last few days and read everything I could about the re-powering issue, including all of the Honda vs. Yamaha posts and the good information in the Montauk re-powering posts, as well as Cetacea p. 56 (13’ re-power with Mercury 40 four stroke). I like the idea of a 4 stroke EFI, but the Suzuki/Johnson and Mercury all seem too heavy, as does the Evinrude 40 e-tec (the 13’ in Cetacea 56 seems to sit pretty low in the stern). I’m leaning toward the Tohatsu 30 four stroke – nice price, lightweight, and the dealer has had good success with the motors at high altitude with carb jets and props changed. He is also the only one who will give me a fair trade-in for the old motor.

Will I be underpowered with the Tohatsu 30? Keep in mind that all I have for comparison is a twenty-year-old two stroke. I’m not looking to break any speed records - I just want the ability to get on a plane without walking to the front of the boat.


Perry posted 12-10-2003 07:36 PM ET (US)     Profile for Perry  Send Email to Perry     
I used to ride my 2 stroke street bike up into higher elevation and with proper jetting changes, was able to regain performance at higher altitude. If an EFI or DFI motor can adjust for leaner conditions a carbed motor can be adjusted, but needs to be done with jetting changes. I also found that the cool dry air up in the mountains helped compensate for the lake of air density.
Bigshot posted 12-10-2003 11:10 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Those are list prices I do some shopping. The 40 is like $4800 and the 30 is $3500. Shipping is about $200 and no tax. Your controls will work with them as well. You will need a new wiring harness and tach.
Bigshot posted 12-10-2003 11:13 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
Oops! I meant the 40 Johnson 4 stroke is $4300. They also sell many other brands so you can use them as a benchmark. Tlynch has a deal going with Suzuki I believe and people are getting 140's for $6500.
JohnJ80 posted 12-10-2003 11:27 PM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
I bet that the new Evinrude 40HP E-TEC would be a really sweet little motor for that boat.

Obviously, I would shy away from carbs. Even if you change jets, the EFI computer is going to have a lot more control more parameters. If you are going to go to the expense of repowering, you should definitely get the EFI capability.

I would also think that idle would be an issue for a carbed motor at altitude. EFI would have to help that problem too.


Sport 13 posted 12-10-2003 11:44 PM ET (US)     Profile for Sport 13  Send Email to Sport 13     
Thanks, guys. Great information!
rbruce posted 12-14-2003 08:19 PM ET (US)     Profile for rbruce  Send Email to rbruce     
I would consider also a DFI such as an Evinrude E-TEC for your repowering. No valve train to adjust, no oil change in the motor, no major service for 3 years...

Four strokes are heavier and mechanicaly complicated. Two strokes are inherently contaminant (perhaps the Yamaha at 100:1 is less contaminant), however, two strokes are simpler to maintain. With the marriage of electronics and two stroke engine simplicity, I would consider first a DFI over a four stroke.

Dr T posted 12-15-2003 01:24 PM ET (US)     Profile for Dr T  Send Email to Dr T     
Sport 13,

I am the "other guy" Nick (Bigshot) refered to on the forum.

I live in Broomfield and have tested a variety of combinations up at Boyd (near Loveland) and on Stagecoach (south of Steamboat Springs) and have posted the results in the Performance Forum.

We should probably get together sometime to discuss. I will drop you an email.


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