1983 36 CONVERTIBLE II,440 Yanmars .What are your numbers?

[Hatt-Trick]

Was wondering what others performance numbers with same boat were.With the twin 6ly2am 440 hp I cruise @2600RPM,19 KTS=30 GPH swinging 24square 4 blades,Peter

[34Hatt]

Was wondering what others performance numbers with same boat were.With the twin 6ly2am 440 hp I cruise @2600RPM,19 KTS=30 GPH swinging 24square 4 blades,Peter

I would have thought better than that what does yanmar show at 2600 rpm?
My 34C with cummins 330bs is 23 kts cruise 20 gallons total.

[madhatter1]

I would have thought better than that what does yanmar show at 2600 rpm?
My 34C with cummins 330bs is 23 kts cruise 20 gallons total.

That's what I get at the same cruise speed with my 270,s. What's your top end? I always wondered what I am missing by not getting the 330's. The 83 36C it a much wider and I think heavier boat than the series 1 36C which is what the 34C became.

[jim rosenthal]

True. It weighs more and it is not a particularly speedy boat. There was a 36 Series I in Virginia Beach a few years ago which had been fitted with Yanmars, I think the 440s, and it was very fast. Like mid-thirties on top end, I think. Probably not very stable, but very quick. Series I 36s are flatter, have more planing surface aft, and weigh a lot less.

Drifting a bit, there are a pair of Series I 36s undergoing refit which are probably going to get the latest iteration of the Cummins QSB engines, at 420 hp each. These boats are likely to leave everyone else in the dust. Well, not the dust, but you know what I mean.

[saltshaker]

Hard to say since there aren't many/any with the same power to compare to. Your performance does seem a bit low. You're running close to what a factory boat with 390HP 671TI's runs. What's the top end, max rpm, factory recommended cruise rpm/speed for your engines? What gear ratio, are you propped right? Repowers can vary greatly with regard to performance. You may need to dial it in a bit or maybe you're cruising too slow? Again, not familiar with your engines but it does seem slow based on what you posted.

[Avenger]

That's what I get at the same cruise speed with my 270,s. What's your top end? I always wondered what I am missing by not getting the 330's.

Are you saying 23 MPH or kts? I've got 260 CATs in mine and it will cruise around 20 kts. I'm having trouble imagining that an extra 20 HP gains 3 kts.

[madhatter1]

27 MPH which is about 23 KTS. 34C. Is yours a 36? That would make a difference. My friend has a 36 and his is longer wider and may or not weigh more. Also max RPM is 2600 and I run 2400 cruise. Maybe I cruise closer to top RPM.

[Avenger]

It's a Series I 36C and my top end is at 2800. That may be the difference. Thanks.

[Hatt-Trick]

I would have thought better than that what does yanmar show at 2600 rpm?
My 34C with cummins 330bs is 23 kts cruise 20 gallons total.

I top out at 3300 rpm,never left it there to see what my top end speed was.It used to swing 24x26 3blades which were paired up to her when she had the Detroits.When I bought her the running gear was beat so I had the shafts trued,changed out all the cutlass bearings& on the advise of H&H propeller,Salem ,Mass opted for 24''x24'' 4 blade.Much smoother ride but lost a bit of speed.I'm going to check the red gear ratio on my ZFs.She is heavy,last haul she weighed 29,750 lbs all topped off.I was curious to what other size props were on the same boat although knowing it should co-incide with power plant and red gear.I'm just trying to see where she stacks up with others preferebly with the same power,Thanks,Pete

[Hatt-Trick]

Hard to say since there aren't many/any with the same power to compare to. Your performance does seem a bit low. You're running close to what a factory boat with 390HP 671TI's runs. What's the top end, max rpm, factory recommended cruise rpm/speed for your engines? What gear ratio, are you propped right? Repowers can vary greatly with regard to performance. You may need to dial it in a bit or maybe you're cruising too slow? Again, not familiar with your engines but it does seem slow based on what you posted.

I'm cruising at what I think is good for the boat at 3/4 throttle.I top out at 3300rpm,Yanmar has them at a continuous throttle at 3,000rpm.I think swapping out the 24x26 cupped 3 blades for the 24 sq lite cup 4 blades might have dropped her speed .I might launch her with another set of three blades and re-run the numbers including the red gear,see what you guys think,thanks,Pete