RPMs/Speed

ckuppens · Post by **ckuppens** » Mon Jun 21, 2010 8:19 pm

I am getting all the bugs out of the new boat. I was wondering what some other gas powered 35's get for speed at Wide Open Throttle??? Before buying the boat I had it compression tested. When I ran it on Sunday I decided to open it up. I brought the RPM's up slowly. The throttles hit the wall at 3350. I left it open for about 45 seconds. and the tachs climbed to 3400. At this point with a full tank of fuel/water. 4 adults and 4 kids on board with a slight tide and 15kt wind at my back I was doing over 20kts. I have reason to think the gauges may not be correct (some other gauges are not accurate and the BY thinks the wires are old and have resistance) Could also be old fuel. Anyway on older 454's does 3400 rpms seem right to get 20.5 Kts?

Mike_Lenz · Post by **Mike_Lenz** » Tue Jun 22, 2010 1:52 am

Chris, I have a 1973 B 35 with 8.1 Crusaders, they turn up to 4600 RMP I can get anywhere from 36 - 40 MPH depending on the wind and load. I changed my props to 4 bladed ones I don't think they helped my top end any but the boat will easily plan at 3000 RPM without having to push the throttles any higher. I hope this helps. Mike.

Post by **dougl33** » Tue Jun 22, 2010 8:11 am

Chris, I would think you should be getting a minimum of 4000rpms and probably close to 25 knots on the pins. Can you refresh my memory as to the trans ratio and prop size you're running. You mentioned full fuel and water, but what else does the boat have? Hardtop, 200 feet of anchor chain, 500lbs of tools and spare parts, etc... Even when I had my hard top installed I could still get 4000rpms and 25 knots on my 33 FBC. The 2 are pretty close in deadrise and weight. Although the 35 is 9 inches wider, I think the 35's extra length makes up for some of that to keep the performance numbers fairly close.

Buy2ls · Post by **Buy2ls** » Tue Jun 22, 2010 10:58 am

If those motors are original from 1979, I would imagine that they are close to the end. Run a comprssion test, If they are all close but a bit low, that indicates that the engines are tired/worn-out. Is this the gas 35 from the Cape that was for sale on YW last winter into this spring?

ckuppens · Post by **ckuppens** » Wed Jun 23, 2010 2:57 pm

Yes.. One engine is a 79 (not original... replaced under original Bertram warranty) the other is new in 1996. The newer engine has 500 hours. The older one has 1400. Late in life but the compression was good 2 months ago. Props are 21x19. the gear ratio is 1.91:1. Yes there is a hard top. The previous owner said they always turned up to 3900 for him so there is some issue. We are hooking up a digital tach to verify the accuracy on the one on the bridge. Checking the spark etc. and going from there. Just wanted to make sure it was also running slow. Sounds like my top end should higher in terms of speed. Compression Readings: Port All 150 psi. Starb. 1-150, 2-125, 3-140, 4-140, 5-140, 6-140, 7-130, 8-140.

ckuppens · Post by **ckuppens** » Wed Jun 23, 2010 4:25 pm

The props were never repitched after the hard top was put on. I felt that was why they only turned at 3900. 3400 is a whole new development

Buy2ls · Post by **Buy2ls** » Wed Jun 23, 2010 4:27 pm

Where you able to seatrial the boat before purchase? if so what did it turn up then? It is possible that your cam or cams could be worn. Thus not allowing the valves fully open. This could explain the lack of speed and rpm. Also cylinder 2 is out of spec. 125/150, the older and more tired engine could be holding the newer one back. I would do a new compression test as well as cylinder leak down test. You can pin point the weak spot better with a leak down test, be it rings, valves or head gaskets.

Buy2ls · Post by **Buy2ls** » Wed Jun 23, 2010 4:41 pm

Hey Ckuppens I have an email from the previous owner that you might like to read. Shoot me your email and I will forward it to you.

ckuppens · Post by **ckuppens** » Wed Jun 23, 2010 6:50 pm

Buy2ls · Post by **Buy2ls** » Thu Jun 24, 2010 2:27 am

from what I am told the email from this site does not work all the time. email me at Buy2Ls@yahoo.com Jeff

Buy2ls · Post by **Buy2ls** » Thu Jun 24, 2010 4:22 pm

Email sent Chris

ckuppens · Post by **ckuppens** » Thu Jul 01, 2010 12:47 pm

I figured I would update you all with the end result. The mechanic looked over the engines and thought the cap and rotor looked old and changed them out. Took a test run. He toped out at 3200 RPMs. I went down to the Marina today and they asked me to pull the boat into the travel lift. At thins point I was saying goodbye to my 4th of July boat weekend! They hauled the boat looking for growth (apparently the river where this particular marina is located in has major issues with barnacle growth..) the props looked pretty clean but they sanded them up anyway. Splashed the boat and took it for a test run. At WOT 4050 on the port and 3900 on the stb. 25 Kts against the tide! My last boat was over powered … this one is under powered (in my opinion) and I will have to keep a close eye on prop growth… something I have never paid much attention to…

Post by **dougl33** » Thu Jul 01, 2010 12:58 pm

Looks like a nailed the rpm and the speed! Glad to hear you're back in business.

Buy2ls · Post by **Buy2ls** » Thu Jul 01, 2010 1:11 pm

Try "Propspeed" it works and lasts multi seasons

ckuppens · Post by **ckuppens** » Thu Jul 01, 2010 2:35 pm

That is what the yard told me. Never heard of the stuff but I will give it a shot next year. Thanks Jeff