98 180 WOT RPMs, Speed
 

Just got my 180 on the water today for the first time this season and got a quick one. I've lost about 10/12mph since last season.

Boat went in for its normal check out. Nothing found - fluid change. Prop was sent off and redone. Gas from last season (filled last part of Oct)

14-19 prop - merc 4.3 4500rpm (does go higher) = 35mph max.

thoughts?

Re: 98 180 WOT RPMs, Speed
 

I say prop. You say it went in for repair, what did it look like?

Re: 98 180 WOT RPMs, Speed
 

not bad some rolled edges small nic or two.
cap, rotor, wires, plugs where also changed at the end of last season

Re: 98 180 WOT RPMs, Speed
 

hmm.. with that prop/motor combo you should be very close to 4800rpm at WOT and 48 - 49mph. I wonder if the hub is slipping a little bit? Or possibly the timing isn't set correctly.

Re: 98 180 WOT RPMs, Speed
 

dead on, last season 48 at 4800 no problem. so i was very surprised today when i couldn't get above 35. it also felt like the "pull" wasnt there as well

is there a way i could check the hub myself or will i need to send it back in. wouldnt the prop shop normally check this?

Re: 98 180 WOT RPMs, Speed
 

Yes, they should have checked the hub at time of rebuild. I just figured out what you said was the prop has already been rebuilt, so I guess I would not suspect that after a professional rebuild.

Do you have a second one to try though as a testl?

Re: 98 180 WOT RPMs, Speed
 

nope dont have 2nd prop. i was going to double check wires and plugs and see if one is out of order or a bad plug. dont make much since with rpms still able to get up there 4500-4800

Re: 98 180 WOT RPMs, Speed
 

I'm just gonna throw this out there as a possibility as well. Since your RPM's are the same what's the chance your speedo is wrong? Too many people view their speedos as the gospel when in fact most of them are wrong. Some are WAY wrong.

Re: 98 180 WOT RPMs, Speed
 

nope verified with GPS about a mile of two difference

Re: 98 180 WOT RPMs, Speed
 

My brain keeps saying PROP? Is there a chance you have the wrong one? Or a different pitch than before?

Re: 98 180 WOT RPMs, Speed
 

Well if your GPS is confirming now that it is indeed slower I will jump on the spun hub possibility bandwagon. Do you have a friend who can let your borrow a prop? If not maybe consider buying a cheap aluminum prop as a backup and test with it.

Re: 98 180 WOT RPMs, Speed
 

going to give the prop shop a call and see if maybe they changed the pitch for some reason or swapped it with a different one. I know the guts are mine they were as nasty when i pulled it off.

talked to my tech today and he's thinking old gas and a loss of octane. His suggestion was to run it almost empty and fill with fresh gas.

37 gal - 4/5 hr run time i'm guessing to empty the tank. i would think low octane would cause a lean condition and maybe burn a piston. maybe hes looking to create some work :)

couple of pics of the prop and hub

Re: 98 180 WOT RPMs, Speed
 

If you are turning the same RPM's as before then its not going to be a pitch change or old gas/octane issues. Your RPM's would change if either of those were the cause. How is your hole shot?

Re: 98 180 WOT RPMs, Speed
 

I dont buy the gas idea either, throw in some fuel additive for the old gas. I hope you figure it out though its got me scratching my head.

I would go to the prop shop and they likely will give you a couple loaners to try a couple different pitches and do your investigation that way. You will need to buy a second anyway, thats something you should have as a backup. And with a couple to compare info on you can really come up with some solid info.

Re: 98 180 WOT RPMs, Speed
 

WOT = throttle all the way down, no more room to more it forward, correct?

Reason, I can reach 4800 RPM with more room to go. I've been real careful not to go any higher but hit 5000/5100 a couple of times by mistake. (Hand on throttle, hit wake, jammed forward).

Re: 98 180 WOT RPMs, Speed
 

Yes WOT is all the way and trimmed up. I believe 4800 is the proper RPM's for the 4.3 at WOT. If you are getting more than that you need to change your prop to a different pitch. If you have a 19 now you would probably need a 21. With changing pitch its give and take. By going up you will lose a touch of hole shot but gain top end speed. The reverse is true for going down in pitch. None of this addresses a different speed this year from last year though.

Re: 98 180 WOT RPMs, Speed
 

You might have the wrong prop reinstalled by accident or old fuel. Bad hubs or slipping hubs will show up just when the boat is planing off. That is the biggest strain on the prop. Within a few hours the hub will slip more and more.

Re: 98 180 WOT RPMs, Speed
 

Well an update. Bad weather has slowed getting to check out at few things. Had the prop checked by the guys that rebuilt it and everything checked good. 14-19" is what I have, Hub in working order. so one thing out of the way.

Next check cap, rotor = good
trace wires = good
checked oil = looks good, no water
pull plugs = cylinders 1-5 good

cylinder 6 plug had some water on the plug. cranked engine a few times no water came out of the plug hole. going to hook it up to the hose later and let it run for a little bit an recheck the plug.

any thoughts?

Re: 98 180 WOT RPMs, Speed
 

Ok so I cleaned and dried the plug. Cranked the motor a few times, very little water came out. Hooked up the hose and run it for about 20 min. Let it cool down. Rechecked oil no water, pulled plug no sign of water......so I guess ill try and get her on the lake this weekend and see what happens

Re: 98 180 WOT RPMs, Speed
 

I am kind of in the same situation... Just got my Z222 out this weekend and can only hit 40 with a good tail wind but really only around 38. I do have a SS 21p prop on the 5.7. Any ideas? Not sure of the last time this boat had a tune up as I just bought it earlier this year. It seems to start normally, acceleration is decent but tops out at 38.:confused:

Re: 98 180 WOT RPMs, Speed
 

Brewfixer what RPM's are you getting at WOT?

Re: 98 180 WOT RPMs, Speed
 

well got it on the water today and all is well. 44mph at 4600 rpm. amazing what a dead cylinder with do. the loss in of the last couple of mph im sure is due to the older gas i still have in the tank.

ran pretty hard today (3 hrs) and burnt maybe a 1/8-1/4 tank. whats the normal burn rate?

Re: 98 180 WOT RPMs, Speed
 

Good to hear you solved your speed issue. I also managed to figure mine out... Seems I was a little conservitive on the trim so i trimmed way up and finally got my boat to hit 54 mph on speedometer @ 4400 rpm's / ~51.3 on GPS. However, umong a few issues i noted... The speedometer does not start working until i almost hit 30 mph. Does anyone know if this would be an indication that it will need replacement or rebuilt? out of the water the paddle wheel does spin freely.

Re: 98 180 WOT RPMs, Speed
 

Good to hear you both have solved the issues, now I have similar to same. I just got her out this weekend and couldn't get the rpm's above 3800 and speed of 42! Just had my SS 21P rebuilt and is perfect, just put half tank fresh fuel in, trimmed it to the point where it would start to porpoise a bit, which was not very much at all.

I was wondering Brewfixer, how much would you bring the trim up? Maybe I am just not adjusting correctly?

And I only had 2 adults and a kid. I am wondering if the fuel we are using is just poor this year, there sure are alot of posts with this same issue. Although you both found actual solution other than that, so not real sure, but I was dissapointed that my buddies Blue Water, with a 5.0, beat me out there today.

Re: 98 180 WOT RPMs, Speed
 

Darn I didn't take a photo of the trim meter but it was just on the high side of the mid point.

Re: 98 180 WOT RPMs, Speed
 

Same boat, similar issue. I have a '98 180 with 4.3 merc. I had to get the Faria tach replaced on warranty beginning of season. The tach seems to read fine low end, but it is either reading low on the top end (WOT around 3800) or I am having an issue. I took a look at the prop yesterday and no identifiers of pitch, but when I purchased in March believe I recall the prior owner had a 23P and I have not changed. As seen above plug/wire issue could be causing loss of one cylinder, but I have a hard time believing that is the case as the boat idles steady and runs smooth. I know some tachs have 4/6/8 cylinder settings and have not had the opportunity to investigate if mine is incorrect. Does anyone know if the Faria's have these settings? Any other thoughts? I know WOT RPM will be lower with 23P, but 3800 seems too low.

I need to get a GPS speed. Based on my prior 20" Chaparral with 4.3 this boat gets up on plane as quick or quicker.

Re: 98 180 WOT RPMs, Speed
 

Duke:

Yes, the Faria tach has a dial on the back that can be set to 4 - 6 - 8cyl. I would suggest spinning it a couple of times before dialing in to the correct setting.

A 21" pitch should run around 4300-4400rpms at WOT so a 23" could be down as low as 3800-4000. I only know one other person on this site that can run a 23" prop on a 4.3L - 180 where most of us run 19" 3 blade or 20" 4 blade props on similar boats.

Brewfixer: You could have a little bit of crud in the speedo line or it might be slightly pinched somewhere. That would cause it to not kick in until there is a bit of pressure built up.

Re: 98 180 WOT RPMs, Speed
 

Mikey, how would one go about cleaning up crud in the speedo line?

Re: 98 180 WOT RPMs, Speed
 

Compressed air after disconnecting the line at both ends.