Bravo II Prop Slipping, Bad Hub?

[mmwjr]

Ua punch and mark the nut thte prop hub to see if they stay aligned.

BTY the picture of he V6's show the raw water pump on the lower left front of he engine, a sure sign they aconnected to bravo's just doesn't say which ones BI, BII, or BIII.

[OceanStateTuning]

Originally Posted by mmwjr

Ua punch and mark the nut thte prop hub to see if they stay aligned.

BTY the picture of he V6's show the raw water pump on the lower left front of he engine, a sure sign they aconnected to bravo's just doesn't say which ones BI, BII, or BIII.

Boat deffinitally has Bravo II's on her.

I took her for a 100 mile round trip this past weekend (Around 2300-2800rpm) and she still slips about 3000rpm up when on the verge of trying to plane off, seems to be both engines actually. Just a slight 400rpm or so slip. I had a buddy in the engine bay while it was doing it and no rubber burning smells. We also marked the hub and prop and took it for a ride they were still lined up on the way back. I do not see any rubber on bottom of bilge.

[mmwjr]

OK coupler and prop hubs are OK. With only losing 400 rpm sounds like it may be the props slipping in the water, loosing their bite. Does this only happen under certain conditions or all the time? Sucking air into water flow causes this.

[OceanStateTuning]

I get barrnicals on my props, I scraped them all off good once and it still did it, not this time out but the last time. My old boat was straight inboard and it would get loaded with barrnicals but it would never slip just not be able to get past certain rpm so I don't think that would be the issue unless outdrives react differently with stuff on their props. But like I said I scraped them and it still did it.

Seems to always happen just over 3000rpm with the boat is trying to get on plane so pretty much a high load condition.

[mmwjr]

Sorry kind of forgot what all we discussed. Are the rpms increasing or decreasing? Do you hear a change in the engine pitch (noise level) and does the boat speed quickly change?

[OceanStateTuning]

RPM's increase and yes you can hear the engine physically changing RPM. It is not skipping or anything, seems like something is slipping/cavitation/or?

[mmwjr]

Well with only a 400 rpm increase and no rubber smeel in the engine compartment I don't think it's a coupler, plus you said both engines are doing it. I am going with cavitation the question is the cause. Once again forgot is this a new issue or did you just get the boat?

[mmwjr]

BTY you mentioned barrnicals on the drivers, how about the hull?

[OceanStateTuning]

Hull as far as I can reach under has nothing for growth... Usually when I pull my boats at the end of season I have nothing except on the metal parts.
I bought this boat back in April, Ran great at first, I had it close to 30mph once but usually I cruise at around 22mph or so until around July this stated

[OceanStateTuning]

Seas were a little rough one day and it was having probably a 750rpm fluctuation, but the other day on my way home from my trip it and I tried it, it was only about 400rpms - it was calm out.

[mmwjr]

And this is with both engines?

Not sure what a common source would be other than bad fuel (have you removed one of the water seperators and dumped the contents into a glass jar to look for water?) or common ground issue that is bad (loose), but I don't know where to look here as most twins have seperate battries,.... .

However I would expect either of these to result in a loose of rpms.

[OceanStateTuning]

Its not a skipping/cutting out issue, it is a slip or some sort.

I drained tanks when I bought boat and fill it up after every use, I've put about 6 fill ups this summer so far in her. Fuel Filters were changed once when I bought the boat and I did them before I left for this last trip.

It started out as just the port engine, both engines do it now. They are on seperate tanks. I have 4 batteries. I cleaned all grounds on engines & power/grounds on batteries when I bought the boat as it was having a starting issue but ended up being the soleniod. I rebuilt both carbs and did general tune up plugs/wires/cap/rotor when I bought it in April. Boat was launched May 9th and has been in water since. I have cleaned the props a few times to get growth off, bottom is clean as far as my hands can go under the boat when swimming around it.

[mmwjr]

Sounds like you have done all the right things. I am at a lose on what to tell you to do next. Sudden increase in rpms with no increase in speed sounds like caviatation. Maybe time to get a mechanic to go for a test ride with you.