Trojan Boat Forum

Pretty much done. Just a few loose ends like carpet and installing the upper helm instruments.

Sea trials went perfectly. Not single glitch. Prop size (17 x 16) is perfect, allowing engines to reach mandated RPM (4100) exactly. Recommended cruise RPM 3600 results in 24 knots speed (see image), exactly where she cruises best. I'm a happy guy.

Sweet ! Do you know what your load is @ wot and 3600 ? ( not sure iF Yanmar shows that on the display ) It looks great Very clean install .

Beautiful job. Interesting I thought that most diesels did best around 2350 rpm. I am no expert but seems 4100 is in gasser territory?

prowlersfish wrote:Sweet ! Do you know what your load is @ wot and 3600 ? ( not sure iF Yanmar shows that on the display ) It looks great Very clean install .

Lots of other data like percent throttle, turbo boosts, various temps, but I haven't seen load. I'll look.

larryeddington wrote:Beautiful job. Interesting I thought that most diesels did best around 2350 rpm. I am no expert but seems 4100 is in gasser territory?

Higher RPM diesels are becoming more common. These are rated at 4,000 RPM WOT, but you are supposed to check and make sure you are propped to actually exceed that and reach about 4100. The Yanmar dealer cannot certify them for warranty unless that condition is met.

DAVIDLOFLAND wrote:

larryeddington wrote:Beautiful job. Interesting I thought that most diesels did best around 2350 rpm. I am no expert but seems 4100 is in gasser territory?

Higher RPM diesels are becoming more common. These are rated at 4,000 RPM WOT, but you are supposed to check and make sure you are propped to actually exceed that and reach about 4100. The Yanmar dealer cannot certify them for warranty unless that condition is met.

Same for Cummins mine are rated @2800 but should be prop to 2900 . Diesel rpm rating are all over the place a DD 671 low hp is 1900rpm one at 485 is 2500rpm , a Cat I worked on was 900 rpm max . Many Yanmars and Volvos are in the 3800-4000 range

prowlersfish wrote:Sweet ! Do you know what your load is @ wot and 3600 ? ( not sure iF Yanmar shows that on the display ) It looks great Very clean install .

Ran the boat again yesterday. It does read the load, but I did not note the reading at 3600 RPM. I'll try to remember to take that reading today.

Load is 85% at 3600 RPM. Is that good or bad or about right? I have no idea.

Great project! I am about to start to repower a 77' F-321. She presently has twin 350 Gas Crusaders. I want to repower to Yanmar diesels. Where did you start to find what Yanmar engines best fit your boat model? Thanks. I look forward to your feedback.

Regards

TT

lumbo wrote:Great project! I am about to start to repower a 77' F-321. She presently has twin 350 Gas Crusaders. I want to repower to Yanmar diesels. Where did you start to find what Yanmar engines best fit your boat model? Thanks. I look forward to your feedback.

Regards

TT

The Yanmar 6BY3-260 (BMW marinized by Yanmar) is the PERFECT replacement for a 350 Chevy. Almost identical footprint, 260 hp, 3600 RPM cruise (4000 WOT), and 350 pounds lighter. Most of the other specs and data are in this topic stream.

DAVIDLOFLAND wrote:

lumbo wrote:Great project! I am about to start to repower a 77' F-321. She presently has twin 350 Gas Crusaders. I want to repower to Yanmar diesels. Where did you start to find what Yanmar engines best fit your boat model? Thanks. I look forward to your feedback.

Regards

TT

The Yanmar 6BY3-260 (BMW marinized by Yanmar) is the PERFECT replacement for a 350 Chevy. Almost identical footprint, 260 hp, 3600 RPM cruise (4000 WOT), and 350 pounds lighter. Most of the other specs and data are in this topic stream.

Is it any taller than the 350?

DAVIDLOFLAND wrote:Load is 85% at 3600 RPM. Is that good or bad or about right? I have no idea.

My limited thoughts

That info has been hard to find from Yanmar . I had in mind 80% as the happy number . But remember my mind is Cummins based . I did find some generic Yanmar info saying cruse rpm should be 85% of rated rpm that would put you at 3400 rpm , BUT this was very generic and maybe pre Common rail /BMW base .

Remember factory rating info tends to be near the max limits . Mine for example tells you can run 1 or 2 hour at WOT or every 8 hours . I would never ever do that . It mabe in the rated use (max) but if you want max life out of the engine running easier is the key .

Was the 3600 rpm cruse in the Yanmar info you have ? I am trying to do more research on Yanmar loading .

I do have a few more questions for you on your numbers ( load/gph/MPG ) at 4000 and 3400 and at 7-8 knots ( what ever rpm that is )

Your sure have done a great job . this engine/boat combo seems like a perfect match

Data that comes with the engines says 3600 is optimum cruise RPM.

3600 yields 24 - 24.5 knots and 1.2 NMPG.

Both engines running at 1200 yields about 6.8 knots and 3.5 NMPG.

Those economy numbers are double what my tired old carbureted 350's gave me.

I haven't yet tried single engine running hull speed, but that was where my best long range economy was found with the 350 Chevy's. I'm hoping for over 4 NMPG.

I bet you will get that 4 mpg , I also bet you may find even better MPG then the 1.2 at different rpms . Got to love diesels

Its like getting a new better boat

Very, very nice.