Marine Diesel Questions

[Chris]

Hi all, long time boat ownerI but new to diesel boat ownership and was wondering if I could pick your brains on a few things. My boat is a 1970 Bertram Bahia Mar that went through a full restoration in 2016. It was repowered at that time by a pair of Perkins T6.354’s at 185hp that were rebuilt from Trans Atlantic Diesel And as of today have about 250 hours on them (I know they are on the small side but I cruise at 16-17 knots and sip fuel so I’m ok with that). They turn up to the max rated rpm’s of 2800 and I’m running 18×23 nibral props with an 060 cup. Transmissions are 2.0:1 ZF’s and shafts are 1 3/8”.
My questions are how far off the max rpm should I run them? I’ve been running 2500-2600 rpms.
Do you think a set of trim tabs would help with my low horsepower application?
What do you think of my current prop/transmission set-up? Any improvements you can think that might give me more cruise speed?
Thank you so much for time.

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[Chris]

Thank you Tony for the information.

[Tony Athens]

The Perkins you have is a “good ol” engine at that HP rating.. Trans Atlantic does a good job bringing them up to their “original spec”.. But realize that “spec” is from the 60-70’s when the engine was developed.. Asking 2500-2600 RPM out of it when you are just making rated is asking all it has to give.. Total operating weight & bottom condition will be the long tern key and to less or more load on the engine from here forward.

Trim tabs–You have to try then to see if they make it easier on the engine to get on , and stay on plane..

Improvement in cruise speed = More engine .. You’d be at 19-21 with a 6BT 210..

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Chris

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