Good morning, new to the forum and first post on here. Bought a 1996 28TE with the Cummins 6bt. Boat ran great when I bought it last fall, gave about 15 kts at 2000 rpm. Since about may I noticed the speed dropping off while cruising at 2000 rpm to about 11 to 12 knots. Figured the bottom was pretty dirty so had a diver do a bottom cleaning a couple weeks ago. Yesterday I go out with a very clean bottom and was getting 9 knots at 2000 rpm with a good bit of black smoke. Even 2400 rpm only gave about 11 knots.
Seems to run normally at low throttle, about 14-1500 rpm, no smoke and 7-8 knots.
Can an inboard prop slip? The engine seems to be running fine, Temps, fluids, all good. Totally at a loss on this and any insight would be appreciated.
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28TE High RPM, low speed
Moderator: Jeremyvmd
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rjhpilot91
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- Home Port: Elizabeth City
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RobS
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Re: 28TE High RPM, low speed
What exact engine?
6BT or 6BTA? JWAC or SWAC?
I would start by checking your charge air hoses and clamps.
Post some engine pics.
6BT or 6BTA? JWAC or SWAC?
I would start by checking your charge air hoses and clamps.
Post some engine pics.
Rob S.
"TENACIOUS"
1974 Chris Craft 36' Commander Tournament
Cummins 6BTA 330B's
(Former Owner)
"TOY-RIFIC" 2000 28TE, 6LP, Hull 408
Luck is the residue of good design.
"TENACIOUS"
1974 Chris Craft 36' Commander Tournament
Cummins 6BTA 330B's
(Former Owner)
"TOY-RIFIC" 2000 28TE, 6LP, Hull 408
Luck is the residue of good design.
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rjhpilot91
- Swabby
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- Joined: Thu Sep 23, 2021 5:48 pm
- Home Port: Elizabeth City
Re: 28TE High RPM, low speed
It's the 6bta. I'll get some pics today, headed over to do some troubleshooting.
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dkirsop
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Re: 28TE High RPM, low speed
A missing shear key at either end of the shaft could be your problem.
Hull No. 1013, 1971
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irishwake
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Re: 28TE High RPM, low speed
Have you checked and cleaned your turbo air filter?
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RobS
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Re: 28TE High RPM, low speed
It's not a prop or shaft slip issue, it's the opposite effect, the engine can not handle the load or you would not have the black smoke you noted. You haven't added prop load and you say the bottom is clean. That leaves you with an air issue. Clogged aftercooler (which you have not stated what model you have or posted any pics), leaking air hose or broken clamp (boost leak), a clogged/damaged air filter as mention above, blocked engine room ventilation. If it started coming on gradually over time you could have a failing (corroding) turbo that is not making rated boost. Ever pull the exhaust elbow off for a turbo inspection?
Last edited by RobS on Mon Jul 25, 2022 9:28 am, edited 1 time in total.
Rob S.
"TENACIOUS"
1974 Chris Craft 36' Commander Tournament
Cummins 6BTA 330B's
(Former Owner)
"TOY-RIFIC" 2000 28TE, 6LP, Hull 408
Luck is the residue of good design.
"TENACIOUS"
1974 Chris Craft 36' Commander Tournament
Cummins 6BTA 330B's
(Former Owner)
"TOY-RIFIC" 2000 28TE, 6LP, Hull 408
Luck is the residue of good design.
-
rjhpilot91
- Swabby
- Posts: 3
- Joined: Thu Sep 23, 2021 5:48 pm
- Home Port: Elizabeth City
Re: 28TE High RPM, low speed
Thanks for all of that insight. The boat being new to me last fall, and then getting slapped with a messy divorce in the new year has made it difficult to go through the boat like I wanted to. I will look into all of those suggestions asap