New to Board Troubleshooting twin 57Gsi

"I know this is going to be lo

"I know this is going to be long, but I need to catch you up so you know what I know.

My wife and I just bought a Formula 280 BR with twin 5.7Gsi's and DP-S drives. We bought it pretty cheap, so we weren't worried too much about things needing to be done on it. We also understood that because it was used in salt water that there would be some corrosion issues to deal with; I don't beleive it was actually kept in the water as things look pretty good, and it still has a super good looking white bottom - my thoughts, it must have been lifted.

Anyway, during the water test when completing the sale I noticed the wide open throttle RPMs were only 4000-4200 on both motors. Some other things I noticed was that it seemed to idle rougher than my father's boat with a 350 mercruiser, and it would occassionally miss when cruising. Since I attributed the ocassional missing to bad plugs/rotor/cap/wires, and hoped the slower rpms would disappear as well, I already changed a the plugs/wires/rotor/cap. However, running the engines on a hose I think I still hear missing every once in a while. The boat isn't under load, so I'd expect the missing to be worse if I actually could take it out. To be honest though I didn't regap the plugs, since I didn't have anything at the time to tell me what the proper gap should be. Anyway, I haven't been able to get it back in the water to see if things are somewhat better yet.

While tearing into things a bit more I found the infamous salt water rust on the risers and manifolds. These have been ordered, but don't have them yet to isntall. Meanwhile I have run multiple compression tests on both engines and am very pleased with the results. On the starboard engine all cylinders ran 190-200psi, whereas the port engine ran 190-200 on all but two cylinders. The remaining two cylinders ran 150 and 160. I think the exhaust valves have some surface rust because the related riser and manifold were in the worst shape of the four sets and exhibited quite a bit of rust trailing down the ports. The engines both have about 350 hours on them.

The thing that is most interesting to me is that they both seem to run about the same, and didn't approach the WOT as stated on the sticker on the top of the intake cover.

Does anyone have any ideas? Does anyone think that the risers all clogged up with rust would also limit my RPMs because of constricting the exhaust, or even constricting the water jackets such that any safety measures within the ECU were activated?

I appreciate it if you made it this far, but I think I've told you what I know."

"I often see posts here from o

"I often see posts here from owners of used boats with complaints of not enough RPMs. Very often these complaints get traced back to the previous owner having changed the props to props with more pitch in an effort to get more speed, or has had the props cupped to get the same effect.
Boat then still not fast enough for them, and they sell it.
Having done the tune up things, I'd check the prop sizing next."

"I don't know what the pro

"I don't know what the props are that are on this, but I do know that other 280 BR like mine get much higher speeds. Probably in the low 50's. We did look at the props, but couldn't tell what they were. I know there are F#'s, that quite honestly I don't even know what they relate to versus inches per revolution. I'm entirely new to Volvo. I guess if the previous owner really wanted to spend the big bucks to get 4 new props all around in hopes to increase speed they could have gone too far and actually put too much load on the engines thus reducing rpms."

Going up one prop size (us

Going up one prop size (usually 2" pitch) will take an engine from 4400+ RPM max down to 4200 or less.

"The intake cover shows this e

"The intake cover shows this engine's WOT to be 4600-5000. I was thinking even going to larger pitch props I should be higher than they are currently, though if I could figure out how to decyhper the codes on the props I might be in better shape.

Aside from the props, any more ideas?"

"I forgot to metion reading so

"I forgot to metion reading something last night that got me thinking about the fuel filters/delivery or even the condition of the gas that's in it right now. I don't know the true history of the gas that in it right now, but was told the people I bought it from "just put about 40 gallons of gas in it." So if the engines are starving for gas or are getting bad gas that could limit rpms too, and bad gas wouldn't help either of them run smoothly.

It seems to me the RPM thing is a common denominator between the two systems, whereas the engine roughness and missing are probably independent of each other."

"RE:"only 4000-4200 "

"RE:"only 4000-4200 " --and-- "thinking even going to larger pitch props"

Increasing pitch reduces MAX RPMS.

Re codes on the props

http://www.volvo.com/volvopenta/na/en-us/marine_leisure_engines/parts_service/pr opeller_guide/propeller_guide.htm

You should have "F" series props. For duals I believe you go up one size(??) from the size indicated on the table (which are for single engined boats)"

"f3 is a 17P, f4 19P, f5 21P,

"f3 is a 17P, f4 19P, f5 21P, with the duo prop its about a 300-400 rpm change, $1500 a set or $750 used on ebay. hope that helped"

"It turns out I have F7 props,

"It turns out I have F7 props, which on the volvo prop chart linked above for my motors equates to approx 52-58mph. I'm not sure how this chart is meant to be read, because every boat will have slip somewhat different than the next model. Anyway, last time I spoke with another 280BR owner at the lake he was easily able to do what mine runs with a single 454, and as he understood it the twin 350s were supposed to be faster than his at 46 maybe.

Does anyone actually understand the volvo chart as it relates to RPM? I'm thinking that relates to 0% slip at rated RPM (in my case 4600-5000), thus it gives you a range of speeds. Then you would have to take into account the weight of the boat and other factors to include slip, which would reduce your speed. I think I've read and it seems true that with twins your slip is reduced as compared to with a single drive."

"Testing out duo-props may be

"Testing out duo-props may be tricky. The reason is you have a very limited speed range compared to single props where you get the maximum speed. You may in fact test up to 3 different sizes that all may land you within the max range for your engine, but with different speed. What happens is that the two props starts working against each other as soon as you get out of the designed speed-range, and thus 'consuming' the power.
A single prop is more like a rubber band with much more flexibility depending on load, power, boat etc.
Bottom line, the Volvo chart gives you the speed range each set are designed to operate within. You will hardly ever manage to get outside that range and over rev your engine. You simply have to test 'one to big' to know where your limit is."

"Re:" equates to approx 52

"Re:" equates to approx 52-58mph. I'm not sure how this chart is meant to be read"

It not really about slip. That speed range for that prop size with that particular reduction ASSUMES that the engine will rev up to somewhere within the 4600 to 5000 rpm range. If the props are "too steep". i.e. too much pitch and the engine won't get to the rated RPMS, then you won't get that speed...
Some folks assume (quite wrongly)... "OOH look! If I change from prop x to prop y, then I'll go z mph faster!!!" Not necessarily. If your present engine/prop combination is gettin you within the recommended RPM range, then changing props will rarely make your boat go faster.

Slip isn't really reduced per se with twins. It's just that doubling the HP (while increasing the weight of the boat by almost half a ton) results in the boat being able to go faster, and that "go faster" is implemented by having a higher pitch."

"RE: "the engine will rev

"RE: "the engine will rev up to somewhere within the 4600 to 5000 rpm range."

Obviously getting higher RPMs would net you a higher speed - no problmes understanding that.

RE: "Some folks assume (quite wrongly)... "OOH look! If I change from prop x to prop y, then I'll go z mph faster!!!" Not necessarily. If your present engine/prop combination is gettin you within the recommended RPM range, then changing props will rarely make your boat go faster."

I'm not trying to be challenging, but why does Volvo put a chart together for different prop sizes based on specific engines with expected hp/tourqe that based on the assumption that going too high in F# will drop you out of the max RPM range? This seems a bit counter intuitive to me, unless the factor missing is the wieght of the boat and the slip/grip of the prop and not being allowed to get any higher in RPMs. It seems that they should limit the F# on engine/prop combinations that shouldn't be made.

Does anyone know instances of other boats regarding weight, HP, propellor F#, mph/rpm? I just curious what other similar boats are doing; I agree my boat is not a feather at ~8300lbs dry, but have a supposed total of 560HP (at some RPM)."

"That chart is supposed to cov

"That chart is supposed to cover the range of boats from small runabouts to heavy cruisers.
For any given "line (i.e. engine) one could have a boat from an 18 ft runabout to a 28 or 30 ft cruiser or..... a houseboat.

If going too high in F# drops you out of the rev range, then you reduce your boat size to stay in the rev range "

"So aside from the possibility

"So aside from the possibility of too high a pitch on the propellor, does anyone have any other ideas for not getting full RPM? Fuel, timing, sensors?"

"I'm not familiar with the

"I'm not familiar with the setup on the GSi versions, but many "electronic" ignition setups have a lead that you ground in order to set base timing. If the lead is left grounded, then your ignition won't "advance" properly (actually, at all) and you won't run very well.

Also...V8 engines will run apparently well with "minor" errors in the firing order. Check (and double check) the firing order, i.e., spark plug connections.

Turn ignition off and remove the flame arrestors. Open throttle all the way. Make sure that the throttle plate is straight up, i.e. all the way open.

Check timing per manual."