Yamaha F150 Twins have different rpms at WOT

[hare2]

Hello,<br />just got my new boat with Twin F150s. Nothing to comlain so far (as expected) besides a different tach reading of 200rpm at WOT. Means 5700/5900.<br /><br />Some facts:<br />16h on motors.<br />New Yam black steel props (not specially matched or blueprinted)<br />Sparkplugs look absolutely identical (8x)<br />No obstructions at the hull in front of props.<br />Both intake throttle valve systems open simultaneously and completely (cables are adjusted)<br /><br />A Yamaha Rep told me, that a difference of 200rpm<br />is quite normal, they cannot match the engines.<br />This may be true, but 200rpm at WOT translate into a power difference of at least 10% (more likely 20%)<br />I would appreciate to hear, if others have simmilar experiences with this package.<br />I know, that no engine is absolutely identical to another one. But above 4000 rpm you really feel the difference, not to mention the trottle levers separating more and more, to get the motors synchronized.<br />I do not complain at all about the overall performance. The boat reaches the speed that Yamaha publishes at there Performance Bulletins.<br /><br />Hope for some hints.

 

[WillyBWright]

Re: Yamaha F150 Twins have different rpms at WOT

Welcome to iboats. <br /><br />The problem could be with your tachs. Digital tachs are usually quite accurate but analog (needle) tachs can vary. Wutcha got?

 

[andy6374]

Re: Yamaha F150 Twins have different rpms at WOT

Following on WillyBWright advice, try swapping the tach senders with the different gauges. See if the same problem persists.

 

[T.Z.]

Re: Yamaha F150 Twins have different rpms at WOT

I have twin f-150s mounted on my Parker. Same deal.200 rpms difference.They couldn't get exact.I would not worry about it. I dont think it affects the performance. But who knows?

 

[hare2]

Re: Yamaha F150 Twins have different rpms at WOT

Hello Willy B Wright,<br /><br />I have the new Command Link gauges. I think they work well--- you can hear if the twins are synchronized.<br /><br />Hi Parker 252,<br /><br />is port or starboard the weak side on yours ?<br />As you need at least 30 more ponies to rise the 200 rpms at WOT this is not a little thing.<br />Would like to get information, whether it's "quite normal" or not.

 

[rodbolt]

Re: Yamaha F150 Twins have different rpms at WOT

your calculations are all wet. a 200 RPM difference is quite normal. however you cn phsically verify the timing marks are in the sorrect poition then phsically verify that both engines have the same advance at wot and the same TPS reading, then physically verify that both have the ame fuel presure at WOT also mke sure that both props re tuned. last grady I did with that complaint had a prop that was out of spec, especially if they are not genuine yamaha props. at 5700 your 300 RPM off what I target it for. a quick session on a dyno or with a test wheel and an inductive tacometer will tell you if its an engine ,prop or hull issue. but the cost of doing this is rather high. unless someone finds an actual defective part its your nickel not yamahas unles you get the hull mnufacturer or rigger to pay. but do a run up on a dyno and you wont find much power difference with 200 RPM. however another trick is to swap the gearcases and props and see if the problem follows.

 

[hare2]

Re: Yamaha F150 Twins have different rpms at WOT

Hi rudbolt,<br />I'll try the gearcase swapping. <br />Would like to know what difference at WOT I have to tolerate and what you think is not "quite normal". There should be a threshold, or am I wrong ?<br />Did not know, that I have to prove that there could be something wrong with one engine. <br />The props are genuine Yamaha ones.

 

[rodbolt]

Re: Yamaha F150 Twins have different rpms at WOT

I think the HP tolerance is plus or minus 15% for an industry stndard. if you dyno the engines or run them on a test wheel and they fall into spec its no worries and is quite normal. however if both can pull the same on the test wheel or dyno you my have a mounting or hull issue, if its mounting or hull its not a yamaha issue. you may also ask to test another prop or style of props. I would like to see the speeds that YAMAHA published for a parker. most likly its published by parker. so far yamaha does not make outboard boats in the states but they do supply some hull manufactures with a product just like the manufacturer of your VHF and bilge pumps. parker installed them but did not mke them. its crazy sometimes but its not like buying an automobile. you would not belive the amount of gearcases and control boxes I see fail cause the rigging was done with the elcheapo super failure prone teleflex cables. then try to find out who is responsible for the warrenty. is it a yam issue, a rigging issue or a teleflex issue? in the end its the consumer that gets stuck about half the time. a lot of hull riggers tend to use the elcheapo stuff, especialy on smaller packages where the profit mrgine is low to start with, key switches are a good one and I have experience with that issue. we had a 7 month old hull come in with a 90 yamaha with a total meltdown of the engine harness due to a defective marineworks keyswitch. yamaha said it was not a yamaha failure, marine works said they only warrenteed the switch for 90 days, the hull manufactuere said their 10 year warrenty only coverd the hull and the only warrenty on rigging items was from the rigging component manufacturer. cost the poor customer close to 800 dollars but in the end yamaha did sell him a key switch assy at cost. marine works keyswitch 22 dollars the yamaha one is about 140.<br /> what my point is is that you have to first identify if there is an actual problem then identify where the problem,if any,lies and who is responsible for it.<br /> also recheck the commnd link setup to insure the trim gauges where set correctly. then verify the tachs with n inductive pickup shop tachometer.<br /> luckily my experience with Parker is mostly positive and they usually use quality rigging and materiels, if it was rigged by prker and not at someplace else.<br /> its the same with cars, if you bought two of the ame model from chevy and tested them at WOT and idle would they be identical or could mnufcturing tolerance allow ome differences. IROC cars are expensive because they have been blueprinted, they are stock but now identical.

 

[WillyBWright]

Re: Yamaha F150 Twins have different rpms at WOT

Do this before you swap gearcases. Just swap the props. If there's a difference in the props, the RPM difference shoud swap with them.

 

[hare2]

Re: Yamaha F150 Twins have different rpms at WOT

Hi WillyBWright,<br />that's impossible, because port side is counter rotating.<br />a.s.a.p. I'll try a different set of props.

 

[WillyBWright]

Re: Yamaha F150 Twins have different rpms at WOT

I was about to ask that. I wasn't aware they offered a counter yet. Hard to keep up on that stuff these days. But considering that, they're obviously made from different molds. So maybe just having one tweaked for a few more RPMs might be an option. It'd probably be the cheapest route. But will you have to pay or will the dealer?