Cummins b or not

[Raymond Slingerland]

Engines are in a Bayliner 3870 which is a 1000 miles away and I am trying to decide if I want to make an offer, fly up there, sea trial and survey. Listed as 1988 250hp Cummins. Unfortunately the boat is 17,000 displacement dry and I want to run 20 knots. The Hino was the favorite engine for them up to 220hp, but with the 250 hp thought I might be able to run 20 knots. To do so however would probably have to run 2200 at least, and maybe up to 2400rpm. Assume it is a 2600 rated engine, hence in the later model engines assume could run 200 under. Appears this maybe a bad idea with this setup. Comments?? Thanks

Topic

[Raymond Slingerland]

early 250

I have already given up on the boat, but Mr. Athens confirms by reasons for my decision. I want to make use of the available power that is in a later model 250hp and have decided for this boat model really need the 315 or more hp engines. Thanks

[Tony Athens]

Have really not followed this thread, but for sure the pics in the first post are of the very first 6BTA 250’s Cummins produced (1987-88 vintage) .. Totally inadequate cooling among other issues.. Think of it a a decent 210-220 HP engine……….Far from enough engine for this sized vessel if you want to cruise on plane..

Tony

[Rob Schepis]

Yup, and better aftercooling and better cooling circuit…

[Raymond Slingerland]

6b

I searched their forum and found one where he had repowered with the 330hp. That did move the boat, but the discussion if they had the 250s in them convinced me I should hold out for more power. Search continues. Thanks

[Rob Schepis]

Ray, any 6BTA repowers on that forum for feedback?

[Raymond Slingerland]

b or not

Yes, I joined the bayliners forum some time back so as to benefit from their knowledge, however, Cummins engines weren’t used in most of their boats I am considering, hence I sought that information from the experts. In this case the boat was a repower. Now the 3788 in later years did use the Cummins. Thanks

[Rob Schepis]

Have you been on the Bayliners Owners Club forum? Seems pretty active..

[Raymond Slingerland]

b or not

Another forum indicates they were pre-b series engines and tend to run hot if pushed. So guess they aren’t a b series engine and can’t be run at 200 rpm under like the b series 250 can. Interesting that the 3870 was less displacement than the 3780 I had been searching, 17500 versus 20,000 even though about the same length. I guess the coring constructions explains that difference. Back to the search and looking for one with the 315/330 Cummins in it. Thanks for the advice.

[Chris Dahl]

Those are affordable roomy boats, but as stated 17Klbs dry and on the first day of ownership….

They tend to squat the more HP you give them. Many in the NW have hull mods such as molded hard chines added and I have seen some with a fairy nice molded swim step hull extension. These mods help this hull a lot with the squat, but as Rob says, you will need more ponies to cruise 20 knots.

[Rob Schepis]

I think you already know the answer – too much boat and not enough engine for what you are looking to do..

An online boat test stated she did 17-20 mph (mph, not knots) on the pins with 175hp Mitsubishi diesels. You’d need to run the 250’s at ~2,400 just to do that same 16 knots…

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