Max Rpm and prop size

[terrymiller1973]

Hi I am new to the forum but not to boating. I recently bought a 1990 238 Pro line WA. It has a 1990 Yamaha 200 on it. The boat runs good and at full throttle it is around 32.4 mph at 4600 rpm. This seems a little low on the rpm to me. Right off hand I don't know the size of the prop. The other thing that concerns me is that if the throttle is reduced back from max the speed drops significantly like at 4200 I am now running 25 and the boat is squatting a lot. If someone could let me know what the recommended propeller size is it would be greatly appreciated. I can check the size that I have tomorrow morning.

 

[99yam40]

Re: Max Rpm and prop size

see if you can get the info you are looking for from this site.
http://www.yamaha-motor.com/outboard/products/perfbull.aspx

 

[terrymiller1973]

Re: Max Rpm and prop size

Thanks for the link I checked it out and cant find a boat that is comparable size and weight with the same HP as mine. I was told by the previous owner that the boat loaded with fuel and standard fishing outfit weighed close to 9000, I really need to find a scale to drag it across to really find out for sure since the guy was oh so honest about everything else. I cant imagine it weighing that much like I said earlier it is a 238 Pro line WA with a cobia tower and not much else except outriggers and a three battery setup.

 

[rodbolt]

Re: Max Rpm and prop size

have the motor run up with test wheel YB 1626.
should turn it 5300 to 5500.
if it can your way over propped if it cannot you have engine issues.

 

[v12mac]

Re: Max Rpm and prop size

have the motor run up with test wheel YB 1626.
should turn it 5300 to 5500.
if it can your way over propped if it cannot you have engine issues.

Take Rodbolts advice, make sure the motor is running 100% right first or you are about to waste money on a prop.

 

[terrymiller1973]

Re: Max Rpm and prop size

I went to the local prop shop this morning and he said the right prop for my needs is a 13 1/4 x15 and said they don't make that for my size engine. He then gave me a 14 something x 17 to try and see if the rpms would climb or if I have an engine problem. I spoke with my mechanic because the guy tried telling me the linkage on the carbs was not adjusted correctly. I just had the carbs cleaned and the throttle and shift cable replaced and the mechanic said the carbs open all the way to full throttle. He also said that the tachometer may not be working properly, but the engine does not sound like it is whining or close to max rpm it is more humming not whining. I plan on trying the prop today.

 

[rodbolt]

Re: Max Rpm and prop size

if all your concerned about is RPM toss the prop in the creek and have a beer.
if you wish not to chase ghosts simply run it up on the test wheel.
if it turns up motor is good prop/hull issues.
if it CANNOT turn the test wheel go find the engine issue.
its that dang simple.

 

[boben2830]

Re: Max Rpm and prop size

Hey you have gotten alot of info here. This boat 238 is this a 24ft boat? If so not much motor for this heavy of a hull. You can make it run good though. I agree you should try a test prop. If you reach the max RPM ( 5500 ) you definatley have too much pitch. Does the motor set on a jack plate? If not you may try having the cup taken out of the prop. Good luck...

 

[terrymiller1973]

Re: Max Rpm and prop size

Rodbolt not trying to cause grief or anything but the gentleman at the prop place did not have the test wheel so he gave me the other prop to try and see if the engine would spin up correctly. Unfortunately the engine did not perform correctly.

I got home today put the prop that was given to me to try and the engine would only turn 4700 rpm. So even with the 17 pitch versus the 19 I only gained 100 rpm at most.

I have my mechanic coming out the first part of the week to look at the boat but would like to have some idea of what may be wrong prior to him arriving. From reading other posts it seems a common problem may be a losing a power pack is this correct or what else might I be looking at.

 

[rodbolt]

Re: Max Rpm and prop size

CDI units rarely fail.
fuel system issues are common.
its your rig waste money as you wish.
my advice ,again, find a dealership with yamaha test wheel part number YB 1626, have them install the test wheel.
back it down the ramp.
start the engine,warm it up for 5 to 10 min then place the motor in gear,accelerate to full throttle. look at the tach.
if the tach reads between 5200 and 5500 all is well with the motor.
if it wont you MUST fix engine issues before wasting money on propellers.
yamaha engineering took the guess work out of testing engine output.
in 30 minutes or so you will know what needs to be done.

 

[terrymiller1973]

Re: Max Rpm and prop size

I will try to locate a dealer with the test wheel that you have stated. The only problem is I am in Key West area and only one authorized yamaha dealer and to say the least they are very expensive. The next closest is Miami and that is about a 2.5 hour tow at best.

 

[terrymiller1973]

Re: Max Rpm and prop size

One other question real quick, the oil alarm keeps going off around 4000 rpms could this have anything to do with the rpms not reaching max. This is the reason that the mechanic was originally coming the beginning of the week to look at this and since he was there I was going to have him look at the other problem.

 

[rodbolt]

Re: Max Rpm and prop size

most likly the filter at the remote tank is clogged.
has nothing to do with the low RPM issue.
but trust me, gotta use that test wheel as no one knows did the engine ever turn the correct RPM or not.
wont be the first time I ever saw folks spend 600 dollars on props before the engine got fixed and another prop purchased.

 

[terrymiller1973]

Re: Max Rpm and prop size

Rodbolt thanks for the advice and I am going to try and locate the test wheel. So far the props have not cost anything the prop shop gave me the other one to try and kept my original kind of as collateral.

Given what we do know already about dropping the pitch and only gaining 100 rpm, would you think it probably is an engine issue. If so you mentioned most likely a fuel issue. What should I be looking at first. I have already had the carbs cleaned.

I also must say the boat when tested was also not loaded with my standard load, it was only me and my son with no fishing load.

 

[rodbolt]

Re: Max Rpm and prop size

first ya simply gotta get a test wheel.
maybe your local dealer will loan it to you with a deposit.
if it spins up then the engine is ok,if not now you have a way to load the engine while the fuel and ign system are tested.
the test wheel is a known engine load and the engineers at yamaha developed them for specific engines and publish what each engine with the correct test wheel will turn.
yours happens to be 5300 to 5500 with test wheel YB 1626.