Out board question

Yes a stink pot question...
We have a Glacier Bay 2670 with twin Honda 150 outboards. I know less than nothing about bigger outboards and more to the point trim. This is a cat and I guess semi displacement? Wondering about outboard trim and what the methodology is for this hull form related to outboard trim. I have messed with it a little on transits but don't really know enough to have a target. The feedback on purchase was keep them all the way down unless the vessel has alot of load and or people. Any insight appreciated.
 

Marty Gingras

Mid-range Anarchist
Haven't used a cat like yours, but trim on every outboard- and I/O-powered motorboat (up to about 35 ft) I've used depends on load, speed, and sea state. Planing boats at speed I trim bow up until porpoising starts then down a touch.
 

billsreef

Anarchist
665
337
Miami
All the way down when hitting the throttle to come out of the hole. Then play with the trim slowly to maximize the speed while still retraining good control. Usually I trim up to point the boat starts getting a bit skittish, than back down a touch. If there is a chop, might trim down a bit more for a better ride. If the prop starts to cavitate, trim down. Every boat is different, so you really just need to get out and play a bit to learn your boat.
 

kent_island_sailor

Super Anarchist
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Kent Island!
I think cats might be different.
What you can do is try different trims until you find what gives you maximum speed for a given RPM.
With a monohull:
Full throttle, trim down.
Once on plane, you slowly trim up. The hull is a lifting body in air as well as water and air is far less drag. You usually pick up speed as the boat is more and more supported by air. At some point the steering will get a bit squirrelly, you stop there and trim back down a touch. This is in flat water. With any amount of waves trimming too far up gives you horrible porpoising. Even in flat water too much up can lead to chine walking with some boats, so there are limits.
In rough water you might want a lot of down and in really rough stuff you are constantly playing the trim and throttle. On a racing powerboat the guy steering isn't the most skilled person on the boat, it is the throttleman ;)

I am not sure how all this translates to cats, they (I think) are not planing boats in the usual sense, the very narrow hulls don't rise up. The lift from the bridge deck is what does this. They also (I think) can run at intermediate speeds, they may not have the black gas sucking hole that goes from hull speed up to fully on plane. A good session with a GPS trying different trims would be a good way to get a handle on it, you also like a mono do not want to be trimmed too far up in rough stuff.

* figure out where neutral trim is, i.e. not pushing the bow up or down. That might be your best bet to start with.
 
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So I played around with it this morning on the way to work. Probably my missing something but it didn't really help at all. One item is I stick to the fuel economy rpm of 4k which varies from 17-20kts depending on current. We were bucking for a bit on pretty flat water, kept bumping trim up from all the way down and it just dropped speed the with each bump, so went back to all the way down. About 3/4 fuel in each tank, the heaviest we run two people and two bikes, wife's electric bike is a bit heavy but overall not crazy in weight. I guess next step will be to run up 500rpm and repeat test to see if it makes a difference. In really flat water you can tell when it pulls out of the water and see a definite gain in speed with set rpm similar to a mono displacement but in any kind of chop from very light up there is no discernable change.
 

Zonker

Super Anarchist
9,732
5,693
Canada
I'd get a level phone on your app. Calibrate it so "zero" is a flattish surface when the boat is at rest.

At speed, with a cat you don't want much bow rise. Say 0-2 degrees.

Monohulls that are planing about 4 degrees is near optimimum.
 
So the learning curve continues... These are Honda 150e outboards. I had a idiot light right after buying and got the Dr Honda kit for diagnostic. I learned the VTEC solenoid had failed on one and talked to one of my guys at work who have me the quick Japanese VTEC tutorial. Using oil pressure to adjust valve timing at higher loads to get more HP. Soooo on the run home today I more or less determined that the the VTEC deadband is 4100 to about 4300 rpm. At 4500 rpm they seem to be solidly online. About 3-4kts consistent bump in speed. Will see how the fuel economy is at this. Definitely alot more engine noise running but it sat right at 1-2deg trim with outboards all the way down. Boat seemed to like it alot. It is very nice running at 4k but a little slower, will see how the numbers match up.
 
So the fun continues...no more idiot lights but on two occasions after about 30-45 min running the port engine starts to surge about 500rpm, set at 4k and it will drop to 35 and back up till you reduce throttle. Definitely in the simple carburetor world I would say fuel supply and probably water. I changed the big spin on from the tank after the first time, also the fuel hose was under the battery box. Thought that might have been it but no joy. Will dig into engine side today and maybe get the computer hooked up to see if there is something there. The Google seems to say fuel supply, coils or flywheel pickup. You can get a OH shit rmp limit to 1800 with overheating or low oil pressure but they are both accompanied by a alarm. Surprised with all the electric gizmos it's not alarming, the previous issue with coil was sensitive enough to trigger a alarm so this leads me to think it's a simpler fuel supply quality issue as the engine would have a hard time identifying this via feedback as I don't believe there is any throttle position feedback it's looking at.
 

Marty Gingras

Mid-range Anarchist
They are black magic. When I had to start managing a fleet of boats with modern big outboards, we started budgeting more money for professional maintenance/repair and less for training of staff to do that. The key was identifying several good shops and developing good relationships with them.
 
Looking online at pics of this model, it seems that foils on the lower unit are at least somewhat popular - which is what I was wondering and why I looked, based on what you've written. Seeing the hull shape at the transom, the 'planing area' of the hull is a very narrow pad and would only act as such at high enough speed to pick the boat up on them - which the foils should help to do, ideally at a bit slower than otherwise. May well be worth a try.
I also agree with Marty, re; 'black magic'. These days an outboard mech has to know more than an aviation A&P. Yuk.
 
They have foils on both units above the wheels. Not OEM by the looks

Ah. Damn.
Sounds like the only other option is one of these... ;)


foil.png
 

Leeroy Jenkins

Super Anarchist
1,569
623
Vancouver
Once you get trim dialed in, use some easy references to repeat the settings quickly - count how many seconds to hold the trim button, looking where the wake starts on the boat, or how far behind the boat the wakes from the outboards come together, or any combination of these. Or you may have your own at this point. I use the first and second - full rpm and getting on step, one, two three, four seconds and the wake should be just at the edge of my peripheral vision. Fine tuning from there.
 

billsreef

Anarchist
665
337
Miami
Haven't worked on any of newer Hondas, but I expect you will find at least one one small water seperator fuel filter on the engine. Possibly also another inline filter, and there is usually a filter or fine mesh screen in the vapor separation tank.
 
Yep, watched a YouTube video on it to see where everything is hiding, has a water separator, filter and another filter in vapor chamber. Based on symptoms the first filter is suspect. Looks like maybe Napa has some or will have to order online. It's wierd it only on this one as I would think both sitting for as long as the boat sat would have same build up. Will do both engines anyway.
 

billsreef

Anarchist
665
337
Miami
If there are seperate pick ups for each engine in the tank, one might be a bit longer and therefore picking up more crap. Good luck on the fuel filters, I have been having a hard time getting some of the more common filters lately. Got a number of work boats with the Racor S3227 filters. Seems everyone is out stock /backordered, even for the Sierra and Merc version.
 




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