Power adders for running underpowered boats at "high altitude", aka Lake Powell

Look at procharger. I live at 6000 feet, and ran into issues with my gutless 4runner barely being able to pull a 3500 lb trailer up a 2000 ft mountain pass. My hp jumped to just under 500 hp and I doubled my gas mileage. I know that procharger makes superchagers for marine purposes. I know apples and oranges, but worth a look. I know propping also makes a big difference. Both pf my boats are propped at 13 with my average elevation at 7500 ft.
I really like the comparatively simple installation, and have also been looking at them for other projects. Seems like it could be undersized or under driven to provide increased manifold pressure, without blowing up the motor at full RPM.

Edit: I drove a toyota with the 22R motor for years, if you run it above 5000rpm they do pretty well. I drove that way for over 100k and gave the truck with 200k to a guy who got yet another 100k out of it. I bet a super on one would be amazing.
 

CRF450R

Member
Hey all. There isn't really a "motorhead" section to this forum, and we are primarily recreational boaters, so I figured I'd give it a shot.

We have a Sea Ray Sundeck 240 2005, with the Bravo 3 behind a 5.0 Mercruiser. All my prior experience was with Alpha drives, and for the most part I love the Bravo, especially in reverse in a tight slot, not so much trying to walk around into the wind, amazing performance in shallow water with it trailered. Coming out through the really bad water 3 weeks ago took our gimbal from loose to sloppy, so were off the lake for a month while I rebuild it. (would coulda shoulda done it over the winter)

The 5.0 is a fantastic motor, most of the time. We get pretty excellent mileage, about 11-12gph at 27-30mph cruising, 7-8gph water sports. Top speed of maybe 37 at 15.5gph with an empty boat, the Bravos don't seem to shine at higher speeds.

The issue we run into is getting on plane with a full load. Once planing we are ok, unless we get into really bad chop (like the channel May-September), then it gets a little dodgy, the big bow likes to "scoop" if you come off plane(looking for a bow cover, gimbal repair first). In the last bad wind storm, we were at maybe 60% load, and the margin of performance was reassuring. We are running Hill Marines 4x4 20 pitch props, a huge improvement from the stock 21 3 blades, really improved the performance and handling of the boat, and improved our margin. Big vote of confidence for Hill. Great service and very fast shipping. I'm not excited about further reducing to the 18 pitch, as I really don't want to give up my cruise performance, and RPM wise we are about right with these props. (I underpitched the last Alpha, great for launching, but you had to manually limit rpm.)

So, Power Adders Has anyone experimented with light nitrous dry or wet shots for short term power, 20 sec or so to get the motor higher in the horsepower curve? Maybe 50hp? Bottle and piping wouldn't add much weight and we have space. Engine isn't really prepped for nitrous, and speed isn't the goal, my hope is a light enough shot doesn't require timing changes, and just makes up for the lack of atmospheric pressure, and the fuel injection can adapt and richen. I also have other projects that I'd like to try nitrous on, so the costs can be spread a little. (cinders hill climb truck, clearly a bad idea, isn't that the point?)
My other thought was a manifold for 3-4 12v blower fans into the intake. Would not be a turbo, but might compensate for the altitude somewhat? A belt driven supercharger is a real solution to the same idea, but I don't want to run it all the time, and I'm not sure how they would do with an electric clutch on them (and fairly expensive). The Mercruiser 6.0 would be perfect, but unless I can find a wreck, would cost a high percentage of the boats worth.

I realize that the rational answer is to take less stuff fewer people or stay fewer days, but with Dangling Rope closed, the fuel jugs alone put us heavy, and we want our cake and to eat it too.
Hi VR, you first of all need a 2.2 ratio drive for Glen canyon in that boat with probably a set of maybe 21's. No mention of these basics until now. 230-250 HP 5.0 GM's have very low torque numbers and a very limited torque curve in the 3500-4200 range and you are as all boats that arrive there are always overgeared and propped. She has to spin up to 5000 WOT to get the engine in a non lugging condition to save the engine. Once the engine can " turn on " then if it is still unacceptable you instead of spending big money on engines, blowers, nitrous, etc. should trade it in for something with far more power. Density altitude is what is killing your power. For every 1000' increment above sea level on a 90-100 degree day you lose about 6% of your power. So you are off around 22% ! What is its max RPM. Also I have had many customers that do not even know how the power trim works.
 

Terry Young

New Member
Many of you know Ray Young (brother) who guided on Powell for stripers for many years; He is in his late 70's and has decided to opt for better medical resources than Page can offer. He has a great Aluminum boat, custom made that has been a great boat on Powell for fishing and family adventures. The boat is 20ft and has a 150 hp four stroke Yamaha that runs out nicely together with a near new Hummingbird Sonar GPS Helix 7. He recently put a new Minkotta 36 trolling motor with Ulterra I -Pilot. Really rigged for fishing or some others commercial uses. The boat is featured this week on KSL classifieds-" boats with motors" so take a look and contract Ray to talk a deal. His Price is: $21,000 which is low for a boat with all its features.
 

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Rainbowbridge

Escalante-Class Member
Been watching this thread, and have to add the 3 cents....(inflation, of course)

had a beloved 28' Bayliner with the 350 (5.7) 260HP Volvo which was ok at sea level, (Dana Point to Avalon, no problem) but a major 'dog' at the 3600 lake....trim tabs were mostly useless.

Was convinced the solution was to put in a 454 until a dear friend, (and a boat mechanic) said: Trust me, if you go to a duoprop lower unit, it'll 'act' like a 454....and use less fuel....he was adamant about pleasure boat propeller 'losses' and had studied submarine propeller technology......what an eclectic mechanic..........

So, I found one from a boat salvage yard in Seattle, went totally crazy and added stainless props, and O M G........he was SO right. She popped up on plane fully loaded, did 30 MPH at only 3200 RPM, so no back barrels open (Rochester quadrajet, in the old days).....and literally HALVED our fuel consumption.(y)

Also, never needed the trim tabs again....actually removed them and all the crazy hydraulic lines and pump.....

So just some food for thought for a fun L.P. winter boat project....

:cool:
 

John P Funk

Escalante-Class Member
Many of you know Ray Young (brother) who guided on Powell for stripers for many years; He is in his late 70's and has decided to opt for better medical resources than Page can offer. He has a great Aluminum boat, custom made that has been a great boat on Powell for fishing and family adventures. The boat is 20ft and has a 150 hp four stroke Yamaha that runs out nicely together with a near new Hummingbird Sonar GPS Helix 7. He recently put a new Minkotta 36 trolling motor with Ulterra I -Pilot. Really rigged for fishing or some others commercial uses. The boat is featured this week on KSL classifieds-" boats with motors" so take a look and contract Ray to talk a deal. His Price is: $21,000 which is low for a boat with all its features.
More eyes will see the ad in "Yard Sale" section. Nice boat.
 
Hi VR, you first of all need a 2.2 ratio drive for Glen canyon in that boat with probably a set of maybe 21's. No mention of these basics until now. 230-250 HP 5.0 GM's have very low torque numbers and a very limited torque curve in the 3500-4200 range and you are as all boats that arrive there are always overgeared and propped. She has to spin up to 5000 WOT to get the engine in a non lugging condition to save the engine. Once the engine can " turn on " then if it is still unacceptable you instead of spending big money on engines, blowers, nitrous, etc. should trade it in for something with far more power. Density altitude is what is killing your power. For every 1000' increment above sea level on a 90-100 degree day you lose about 6% of your power. So you are off around 22% ! What is its max RPM. Also I have had many customers that do not even know how the power trim works.
I have the 2.2 drive and 20 pitch props. At cruise I run 4000rpm and it does well, just can’t get on plane. With full load I’m a little over propped and can only get to 4400 WOT. Empty about 4700. Proping down even farther should fix the launch and get me more RPM at WOT, but puts me in the worst part of the fuel consumption curve. Right now it costs me 4gph to go 4 mph faster. There’s a reason go fast boats don’t run Bravos…

The 383 stroker option above has captured my attention, I really hadn’t thought through how much of my current installation I could keep, and had anticipated a much more involved repower. I have heard that the 5.0 headers are a little small for a bigger motor, but I haven’t seen anything definitive, and I’m unsure why Mercruser would have multiple header castings for blocks with the same architecture. I adjust my trim tabs by counting with the switches engaged. Just about exactly 5 sec full up to full down, and pretty consistent flow to both tabs now that I’ve got the lines the same length.

I live at 7000 ft, but ride Moto in Phoenix during the winter. I’m pretty good at jetting for charge density as a result, though my new KTM500 has FI and I love it. I’d consider a cold air intake or even better an intercooler as cooling water is limitless, but without super or turbo I’m not sure it would make much difference It’s warm under the cover, but I’m convinced it’s cooler than under the hood of my truck.
 

Lake Bum

Well-Known Member
I would sell the boat you have, and replace it with one that is a better power/weight ratio. Toys come and go around my place like wildfire. I went through 5 boats in 8 years at one point. Didn't even blink an eye.
My boat is a 232 Rinker cuddy, with the 350MAG mpi, and Bravo3 drive. With my props at 24's, this has been the absolute BEST match made in Heaven for Powell. I've got the low end power to pull skiers/wakeboarders, and if I just choose to cruise at 28mph I can get incredible economy. I had a 21 foot Maxum cuddy with the 5.0, and hated it's lack of power. I've had other boats with big blocks, that drank gas like nobody's business.

Instead of sinking a small fortune into your 5.0, I would just sell and replace.
 

Lake Bum

Well-Known Member
And by incredible economy.......several times, I have gone from Wahweap to the Escalante, spent 4 days, and came back without adding a drop of fuel. I have a 73 gallon tank.
I've also gone from Wahweap, to 15 miles deep into San Juan, fished for 3 days all over it, and back without adding fuel. All of that done, with never having a complaint on lack of power. Nothing is worse, than an underpowered boat!
 

Slots-R-Us

Active Member
I have a SeaRay Sundeck 24' with the 6.2L engine and Bravo 3 outdrive. It is close to ideal for me on Lake Powell. I can load it heavy and it still performs well. Normally I do not use trim tabs unless I have a heavy load or a funky front to back loading configuration and then they are helpful. As many have stated, the 5.0 liter is just too small for that size boat. I have a 19' fiberglass with the 5.0 engine which has seen most all of Lake Powell, most of the time heavily loaded with people and gear. I used to really struggle with hole shot on that boat. Working on prop pitch, going to a stainless steel prop, and adding simple gas piston trim tabs to that boat made a HUGE difference. If you don't have trim tabs, they would probably help but you just can't get past the torque deficiency.
 

Dungee

Escalante-Class Member
Prop size is immensely important. Had been running a 15” four blade and it did the job on our 115 four stroke, last week put a 13” stainless four blade for a Gorge trip. Instantly had unlimited control of the entire range of RPM’s and could plane at will. It’s kind of hard to contemplate the difference the prop makes until you test it for yourself. Even going from aluminum to stainless will make a difference.

BTW, caught my biggest smallie ever up there Sunday.
A306BCED-5924-4FB4-90ED-83ADEEB5BBB7.jpeg7E9D9D52-DE2F-4ED6-A93B-913A272075D2.jpeg
 

Bill Sampson

Escalante-Class Member
Prop size is immensely important. Had been running a 15” four blade and it did the job on our 115 four stroke, last week put a 13” stainless four blade for a Gorge trip. Instantly had unlimited control of the entire range of RPM’s and could plane at will. It’s kind of hard to contemplate the difference the prop makes until you test it for yourself. Even going from aluminum to stainless will make a difference.

BTW, caught my biggest smallie ever up there Sunday.
View attachment 18963View attachment 18964
Nice fish
 
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