Cruising vibration

[Steeldieman]

Today I went out on a short cruise on the Chicago lakefront.
After puttering around for a half hour at 7 knots I bumped it up to 2000 rpm and experienced quite a vibration and shutter . I limped back in and checked to see if I fouled the prop or struck something. I eliminated those two possible causes. I ran throttle only and it ran smoothly but only at 1500 rpm ( I assumed this feature is limited to 1500 rpm )Later on ,about an hour or so I got a hold of a more experienced hand and went back out . In a two foot Lake Michigan chop
I ran wot at 17.5 knots but only achieved 3150 rpms without the troubling shutter and vibration. Normally I’m able to get 3350 rpm and 22/24 knots at wot. I want to be clear that I don’t run wot often or for longer than a few minutes.
One other issue is that my engine hatch will not articulate and I’m not sure how to add fluid. What could this be and does Volvo need to look at this ?

 

[BradOwens]

For the hatch, make sure the trim tabs are all the way up. They use the same reservoir as the hatch, so if they're down the reservoir will not have enough fluid to raise the hatch.
The vibration could be from a number of causes. I would suggest having a diver inspect the running gear.

 

[BB marine]

Today I went out on a short cruise on the Chicago lakefront.
After puttering around for a half hour at 7 knots I bumped it up to 2000 rpm and experienced quite a vibration and shutter . I limped back in and checked to see if I fouled the prop or struck something. I eliminated those two possible causes. I ran throttle only and it ran smoothly but only at 1500 rpm ( I assumed this feature is limited to 1500 rpm )Later on ,about an hour or so I got a hold of a more experienced hand and went back out . In a two foot Lake Michigan chop
I ran wot at 17.5 knots but only achieved 3150 rpms without the troubling shutter and vibration. Normally I’m able to get 3350 rpm and 22/24 knots at wot. I want to be clear that I don’t run wot often or for longer than a few minutes.
One other issue is that my engine hatch will not articulate and I’m not sure how to add fluid. What could this be and does Volvo need to look at this ?

The vibration could be from many things. From reading the post it seems as the vibration went away. I assume from your post you checked the props condition and found no damage. If the vibration issue went away when on your second run I would suspect you have have picked up something in the prop and fouled it. (a line, weeds, large garbage bag) I know the weeds in Racine harbor are starting to reach the surface of the water are the Chicago harbors too? I had a fouled prop from weeds when cruising on the Tennessee River. A couple of times shifting into reverse cleared the prop of weeds.

The RPM issue (3150 WOT) is too low, (3350 WOT) is really too low too. Is this the first time you noticed 3150 RPM this year? Were your trim tabs activated? You indicated that the engine hatch would not go up. Are you stating it didn't go up at all or not all the way? As stated by BradOwens if the tabs are all the way down there isn't enough fluid in the reservoir to have tabs fully extended and lift the hatch all the way. But the hatch should lift partially. Do you hear the pump running when you are trying to lift the hatch? If you hear the pump running but there is no movement I would first retract the tabs all the way. I would check the fluid level. The pump/reservoir is located under the aft seat. To inspect the level you remove both beckson plates under the seat, flash light thru one and look though the other to see level. To fill the reservoir the seat needs to be removed and plastic storage box.

This shows the location of the trim pump in my C26. Your boat doesn't have the waste tank there I believe your generator is there. The pump is just below the steering cylinder. I think it is in the same location on the C28.


RPM issue, Basic, how many people on board, extra gear on board, water tank, fuel tank and waste tank levels, sea conditions all will effect RPM. Trim tab operation, fuel filters fouled, Prop damaged will also. I would check all the basics before getting a Volvo Tech involved.

When you resolve RPM issue and you find that your normal running WOT is back to 3350RPM I would log WOT speed and rpm, log it several times this season in different sea conditions, Gear, passengers, fuel ,water and waste tank levels. Keep a log rpm and speed. During the off season I would take the prop to a good prop shop with log information and have them tune the prop so that Max rpm is a minimum of 3500RPM and max is 3600RPM based on the way the boat is normally equipped. I have used Air Marine on Ashland Avenue by the Airport. He is an Acme prop dealer. Acme props is what Fluid Motion uses.

 

[trailertrawlerkismet]

The lower rpm’s could be from a slight growth on your hull. It doesn’t take much to slow down the rpm’s.

Jim

 

[Steeldieman]

Thank you everyone for replying to my post. I’ve scheduled a diver to clean and inspect the bottom. Once he’s completed that work I will go out and see what the results are . Brian
Thank you so much for the information and reference, I never know who to use for this stuff. I don’t mind paying I just want it done well fluid motion should be paying you for the service you provide on this site and I’m personally grateful to you. I’m going to have the prop tuned in the off-season. Oh , I was running in a sloppy 2 ft chop that I almost described as 2-3 foot. 3 160 lb men full full & water , ten gallons of waste. Prior to the issue I had pushed the rpm up without the issue. The guy I use for help around the harbor has been reminding me to use reverse if I feel like the props been fouled. I have to admit it’s a bit disconcerting when you get that vibration, it rattled me a little.

 

[Steeldieman]

Diver found a bent prop. I didn’t see or hear anything and was in 40 feet of water. Any idea on cost of new prop ?

 

[baz]

Cost for a new prop would in the region of $3,000.

I just had my damaged prop (two slightly adjacent blades bent about 1/2") repaired for a cost of $333 and this included a static balance.

I did feel a slight vibration at over 8 mph at the helm wheel with the two bent prop blades. I had hit 3 logs prior to the collision.

I had my diver serviced pull the prop off and sent to my local prop shop a few miles away. They took 3 days to return the prop to me and it will be re-installed tomorrow for me by diver service.

 

[Steeldieman]

Yeah, it gonna be a repair only job I think. I posted a picture of the damage in my album. I never saw anything or heard a strike.

 

[BB marine]

Wow bumped some hard water on Lake Michigan. I gave you wrong information about Air Marine.It is on Central avenue. A fellow TugNut messaged me. If you have a shop straighten the prop I would give him your engine specs and max rpm they may be able to tune the prop at the same time it is straightened and balanced . I know of another Cut owner C28 max rpm just below 3400. He had the pitch reduced. I don't know how much. Now he turns 3550 with no loss in speed. Less load on the engine.

 

[Steeldieman]

Thanks Brian, I drive by that shop like 5 times a week, I have a customer right there. The diver is going get it in to them tomorrow. I’m going to stop in and go over the repair and pitch with them sometime this week.