1979 Viking build

[rjdubiel]

whats a chipped ecu? a 11350 digital with a promax chip? The more compression use use the more fuel you will need. You can reuse head gaskets as long as they are not super old. Like brand new and run it a few times and swap heads and reuse the gaskets, just keep them on the same side of the motor and should be fine and the spark plug will tell you if water is getting in. What rpm were you at when ya got 87? I assume on the limiter at about 6800?

[LakeFever]

My stock A8 ecu which I sent for testing has the enrichment cycle set to 5800 rpm and it was hitting the wall at 6200 rpm before the head swap. With the tighter heads I can’t say for sure it’s max rpm but I did glance at the tach once when I was pretty well full out and it was 6500 so I’m pushing the full rich over the top. I was somewhere in this range at 87. Around 6500

The chipped ecu I have is a 225 Promax A17. The tune work was done by CDI some time ago when this was still a service being done. I gather Merc is now out to get companies who offer this service nowadays. and from what I understand of the process the potting material is removed. The eprom is removed and reflashed and then it’s all repotted. I was told it was a 225 promax ecu with no modifications to the fuel curve just raised limiter before full enrichment to 7600. I ran it once on my motor before the head swap and it ran great. Sounded mean. But drank noticeably more fuel so I put the stock A8 200 ecu back on. I was checking plugs and saw it was still quite rich so I put the small chamber heads on and loved it. It’s still rich so I do want to run the A17 box again but with an adjustable fuel pressure regulator so I can try and dial in the mixture a bit. I’m also wanting to shave these small chamber heads down a bit more first. Probably all will be next spring. Having too much fun right now as it is

[rjdubiel]

OK, I got a 11350 digital box that has a 225 PM chip in it. Never ran it as i swapped the chip to use on my 280.

Anyway, Run that box that should rev to 7600. Do you have a 26P prop, chopper? Run that and see if it will turn up, if it does you should run about 90-91. then try a 28P to see if you have the HP to turn that over 7K . I am guessing you don't have the compression to get a whole lot more RPM than 7k with a 28P but I could be wrong. Very careful lowering fuel mixture. you may be rich up top but mid range can go lean and you can fry the motor running 4-5K! So do a mid range plug check also if you start with the fuel pressure messing around.

[LakeFever]

That’s a solid plan RJ thanks. I do have many props from 22-30. 22+24 small ears. I will be super cautious with the fuel pressure tuning. I have a full box of new plugs and I’ll figure out the leanest hole and use that to read. Drop 1psi at a time and check the plugs mid/high all that. Slow and cautious process for sure I’ll likely spend and entire day or more messing with this when I get to it.

For my next day out I’m going to lighten the load, run the hoss 28 again and see how it does. I might try the 30 again too just to see how it goes as well.

[rjdubiel]

I would put the mod box on and run a 24 and see what it will turn to make sure it actually goes higher than the stock 6800 limiter. If it does start with the next taller prop and see what you can get it to for RPM and Speed. Usually lack of compression keeps the motor form climbing in RPM with taller props. I run into it with my 280, has 145 to 150 per hole compression, but i need more to turn a taller prop for top end. with a 28P i can get about 8K, if i go to 30P speed is about the same but RPM drops.

[LakeFever]

It’s been busy lately but I finally managed to get back out yesterday. Fantastic weather and a great run. I ran with some other guys so I left with a full tank and took my tools just in case. It got dark before i wanted to stop running but with a half tank and my weight I managed this. I’m not one to embellish things but I’d say it ran 90 if we use a rounding method

[LakeFever]

Managed a run the other day and I decided to try the promax ecu again. It sounds so much rowdier with that box than the A8. If all I wanted to do was show off? This is the brain to run the sweet merc crackle and off throttle sounds are very, very cool. It did run very well and it seems to have more snot in the mid range but it’s using a ton more fuel even with the small chamber heads. Interestingly enough it did run the same speed as the A8 box with this Hoss prop 88mph. The conditions were awful, the wind was 25+mph and crossing the lake to the river was insane the waves were 3-4’ I got soaked. The interesting note here that I definitely saw was the tach hit 7000RPM at one point, I’m guessing this was during my fastest run. Another very interesting thing was this run was mostly full of fuel and man did it ever set nice. Once past the chine at 80 it settled right down and drove straight effortlessly. So I definitely think with better conditions and less weight the promax ecu will run a bigger number. The plugs are dark brown and wet so I can lean this thing out more which I believe will be the ideal mod at this stage. My ignition timing is also set to 23 degrees, I’m wondering if I should bump this up to 25 do any of you think this will help top end or just acceleration?

I did buy an adjustable fuel pressure regulator that I thought was a bolt on to replace the VST regulator but it’s too small. Does anyone know of a bolt on aftermarket adjustable fuel pressure regulator that will fit on the VST?

[LakeFever]

Tore a VST apart and got to sorting out an adjustable fuel pressure regulator. I was going to install a new stand alone pump/filter/regulator but pumping a return back into the boat didn’t sit well with me. It just feels and is dangerous. Also with a siphon feed fuel tank and installing a dry stand alone pump I didn’t want the hassle of priming issues and all that. Finally my VST works perfect and it’s whisper quiet so why take perfectly good parts off for the sake of it? So, I went to figuring how best to add the adjustable regulator to the VST. Initially I was going to drill out the VST cover and tap that with 1/8 npt but after some more studying felt this to be unwise. I decided to take the factory fixed regulator off and found a way to adapt it instead. Goes like follows

remove reg and cut off metal diaphragm cap with band saw


drive out stainless orfice. It’s sitting on the bench in the back of this pic.


drill and tap that opening 1/8 npt


shorten the little tubes under the screws about 1/4 to make the clamp hold properly. I smoothed out the saw marks off of the factory regulator chassis first. Installed a 5/16 barb into the opening


Made a small aluminum angle bracket to hold the adjustable regulator I sourced from Amazon right behind the ecu directly above the VST. Using the factory vst hose I cut the one angle off so it was just a 90 and using stainless cinch clamps ( same as Merc ) I installed the return side of the hose. I used a 1/8 npt 90 out of the bottom of the reg and another 5/16” barb. Then I used a piece of 3/8 fuel line and made a loop from the input side of the brass fitting above the vst to the regulator again cinch clamps. I used 3/8 line because I had marine rated on hand and the barb on the vst is quite large my 5/16 marine line struggled to fit over it. I’ve tested it no leaks at all, everything good. Bunch of pics to show how it turned out. I’m a little leery of that pressure gauge it’s a cheapo regulator and the gauge is small indexed incrementally every 5psi which is not really fine enough for my goals here. I’ll be modding that shortly with an improved gauge and probably a bleed port too. I hooked up the factory vacuum line as well I think you can see it in one of the pics. It’s facing to the rear of the motor.

[LakeFever]

Got a liquid filled 0-60psi gauge. Indexed it to see the 40psi area the easiest. Added a schrader like oem for bleed and mainly so I could verify the gauge accuracy. I figured so long as I set the regulator to the same number showing on my tester I used on the factory regulator then even if the cheap gauge was off I could have a safe baseline to start with. Thankfully both gauges showed identical pressure so I’m considering this regulator mod good to go. Got a box of new plugs and I’ll be back out to test the promax ecu and some fuel pressure tuning soon

[LakeFever]

We are in the zone here gents. The regulator itself is a pos and heading to the bin I should have known better and bought an aeromotive. It is so sensitive in the 35-40psi range which is where I need the adjustment it made it very hard to dial in. That said I did manage to get this thing leaned out to pretty much perfection and wow she’s flying now. Major improvement. My previous best with the Hoss 28 was 88. My fastest ever was 90 with the 30 srx. Today I ran 93 with the 28 Hoss with 3/4 tank of fuel and tools etc on board not at all my lightest possible set up. I was running a river and ran out of room and courage a bit because I didn’t try for max trim. This hull above 90 sets right down and just runs straight as an arrow it just gets a lot of lift from the air. No chine walk at all above 90 though, it’s actually a bit weird because it’s as easy to drive there as 60. The big difference being the nose is high and pretty light at 90 so I didn’t really try to bump in more trim to test the limits like I did when gunning for my previous best. I just set it where I like it and let it eat! A super satisfying day I’m very pleased with 93 on a 28 at 7200rpm give or take because I’m glancing at the tach at those speeds not staring at it. Also as expected my fuel consumption is way down. It still drinks a little more than the A8 box but it’s spinning a lot higher and I’m running harder so that’s to be expected. Although I didn’t run it out to max speed when I had it set to 34psi the thing ran like a wild animal. The acceleration was insane but the plug was just a wee too white around the electrode for my liking so I fattened it up. It likes 36 psi it runs great there and the plug looks decent. Piston wash it’s hard to tell because I cleaned em off with that 34 psi run haha. If I can get out again I’ll try the 30 one more time but I probably should just stick with this hoss the hull loves it and it’s easy to drive.



I posted the rest of the spark plugs in this how to read plug color thread
https://www.screamandfly.com/showthr...45#post3435545

[LakeFever]

New aeromotive 13129 fuel pressure regulator installed. Much more stable. Testing again soon might try my 30p again but I want to keep the prop a constant to track gains. This regulator is a bit taller with the an-6 fittings instead of npt and man is it close to the cowl. I had to file the top of the threads down a whisker to get some clearance. For mounting I used the bracket that came with the regulator, cut it down, and welded it to a small 1/8 stainless plate. There’s two 11/64” holes on the top of the laser that were already for #12 self tapping stainless screws. Much cleaner bracket than last time

[LakeFever]

I managed to squeeze in another test run but had no success with gains. First I did the dumb move of using my boat ratchet and plug socket at the shop and didn’t I leave it on the work bench? Lesson relearned. Don’t use tools from the car/truck/boat tool kits in the shop. So that killed the ability to read the plugs. Second, massive wind gusts. I got one run up to 85 and a gust of wind came at me and man did the whole boat ever lift high. Freaky. Third and most unfortunate I met up with a fellow fast boater who blew his lower unit and I had to tow him back to the ramp. All that aside it was a fun run but no chance to do any meaningful tuning. One interesting aspect is I did set the new regulator to 35psi and the plugs when I got home were dark, and wet. Plus I’m used to the engine sounds now and it sounded fat again. Loads of black soot on the prop too so definitely needs fuel pulled out further. I attribute this to the aeromotive flowing more or better than the cheapo I had on previously. I’ll try and get out again but the time is running short now for this year. Starting to see frost in the mornings

[LakeFever]

Well here we are after a long cold spring finally back at testing and tuning and working the set up. I was on the hunt all winter for a 30hoss and came close but no cigar. I did manage to source a 30p lightning et though so aside from the four blade stuff I now have all the three blade gofast prop inventory on hand. About that et, I have to say it is a bit of lunch bag letdown after running it. It is fast yes no doubt but it’s not the best feeling prop, at all. In fact I’d say that worked 30p SRX I have is slightly better feeling and I don’t particularly care for that one either. I believe this to simply be a matter of personal preference because there is no denying the performance of both they are fast it’s just that they push the hull rather than lift and hold the hull which I have to come to prefer. I like a prop that feels planted firm with solid grip, confidence inspiring which neither the et or the SRX are, until your flying that is. Once I’m over 80 and the hull starts packing air the et is great and the SRX is pretty solid too. The et runs the boat a lot flatter than the SRX or my favourite the Hoss. The hoss is a completely unique animal it’s nothing like an et. The hoss is chopper’ish but has this odd and for me at least very pleasing effect of pulling the transom into the water while lifting the bow at the same time. So while the hoss does fly the bow higher than the et or SRX it is planted and easier to handle at any speed. I will concede though that as speeds move upwards the et becomes the nicer prop it does feel safer at speeds over 80. Up until 80 the hoss is 10x better to run in real world conditions it’s a heck of a lot easier to drive. The hoss does generate more porpoising though so there is a price to everything. In terms of blow over the et really doesn’t make me worry about that at all where the hoss does flirt with that thought rolling back of mind under a hard pass. The et also has a strange over trim reaction where the hull goes from fine and dandy to pulling huge wheelies and wobbling all over the place. There is little to no warning for this where the hoss never does this. It will lift the bow up and up with more trim and chine walk like crazy as this happens it never makes me feel like it’s going out of control where the et goes from calm and cool to “uh oh” which surprised me considering all the et fanfare out there. I could go on about props for a while but I’ll have more to say after a full season with the et to be fair. Anyways back to tuning and testing.

So the new regulator is nice and I can accurately control the fuel pressure. I have been inching up to the right plug read and I’m still a bit fat. I managed a 90mph run yesterday with the new et around 6500rpm in very poor air quality. I’m running the promax ecu and fuel pressure at 31psi with timing at 23 degrees. I will be turning the fuel pressure down to 30.5psi next time out. It is getting closer to ideal so half pound bumps only. I do think I have pretty much reached the max power level of this powerhead though especially considering the srx, hoss and et are reaching pretty much the same speeds. Once I get the air fuel dialed in and get a day with good air I can see 95-97mph on a perfect pass with the et but I don’t see 100 out of it. Maybe if I run with just a couple gallons of fuel and take every bit of weight out, maybe. But I don’t consider that much of anything. In the drag racing world a car that runs 9.99 in the quarter is called a solid ten second car not a 9 second car. That’s how i see this boat it’s a solid 90mph rig and im very happy with that. For now

i am slowly working on the 260 power head and hope to have it together this year. It would be nice to get to a solid 100mph boat. Maybe 103 or something like that to put it solidly in the zone. Probably won’t run the new power head until next spring though so for this year it’s mostly rippin around as is.

[XstreamVking]

Sounds like your having fun with it...This is when all the hard work pays off...

[LakeFever]

Stator took a dive this week. I think I might have nicked some of the epoxy off the windings this spring when I swapped flywheels because it had a tiny stumble under acceleration right from the first time out. It was so slight I could barely detect it at first. This past week it became quite noticeable and the low speed acceleration was definitely off so I dug in to see what was going on and found a burnt winding area. Fortunately I have spares so a quick swap and I was back in business. The acceleration is so much better now. I am running close to 15v when under full throttle though which might be a bit high so I’m going to investigate the voltage regs and see if they are up to snuff. Tuning wise I have it dialed in good now no further adjustments needed. It runs strong and gets good mileage and the plugs look great. Prop testing a ton but it’s a 90mph boat it’s never going to be a 95mph boat all day every day with this power head. It is a ton of fun to drive as it is but until I get the new power head together I’m calling this engine sorted.