3600rpms?? 44mph. Should be 44-4800rpms

[WAVENBYE2]

Some of you already know what I have, it's a 91 Bayliner Capri 2050CX,mercury mercruiser V-6, mercarb 2bbl,Thunderbolt IV, alpha drive. prop 19p 3bld. I changed the plugs,oil & filter. OK I took her out yesterday, first time since last season, winterization AOK. cooling sys AOK, Temp 140 all day, she ran great, I am getting 3600rpms max, But shouldn't I be getting between 44-4800rpms? If I can get her up to 4400rpms I feel I should be getting at least 50-55mph not just 44mph top out speed, What is the best way to increase the rpms with out me doing some thing wrong and messing up the engine?? I learn every day so I feel its best to ask first before I just do it and find out the hard way later what I did was wrong, Wanting to increase rpms to increase speed. Could it be as some thing as simple as the prop.19p 3bld quicksilver?? has been slightly damaged before, just buggered a little , I smoothed it back out. Thats every thing...Or can I adjust prob. from the engine,what would you do or check??? THANKS PAT

 

[Don S]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

You won't get 55 mph, but you should get more rpm. You need a good prop to test with, not a patched up one. And you need to verify the tach is accurate, and you do need a LOT higher WOT rpm.

 

[WAVENBYE2]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

OK I will start with the prop first, Don I would like to ask one YOU thing before taking this to another forum, I have asked in props forum with out a straight answer, its a (j)533 quicksilver 48 16318 A4, this is what has me messed up it looks like 19 stamped over the top of 21p, I really value your opinion on this Don, I spent 2 hrs trying to find it ,with no luck >>THANKS AGAIN PAT

 

[ziggy]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

OK I took her out yesterday, first time since last season, winterization AOK. cooling sys AOK, Temp 140 all day, she ran great, I am getting 3600rpms max, But shouldn't I be getting between 44-4800rpms?

so were ya able to obtain 44-4800 last year? did you change props from last year? to me if ya could get yer rpms last year, and ya didn't change props. i'd look at the engine for proper operation before switching props to get the rpms back.

my ol boat is much different than yer new one. but i could barely reach my wot with a 21p aluminum. a 19p aluminim brought me right up to the top of my wot.

it'd be better to not have a slightly buggered up prop.....better to have them pristine.

 

[Don S]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

so were ya able to obtain 44-4800 last year? did you change props from last year? to me if ya could get yer rpms last year, and ya didn't change props. i'd look at the engine for proper operation before switching props to get the rpms back.

Ziggy has the question that has to be answered before you change anything.
Props are only going to change your rpm between 100 and 150 rpm per inch of pitch or diameter. You are missing close to 1000 rpm.

 

[WAVENBYE2]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

To be honest with you, I believe the rpms are the same as last year, I say this because the mph is the same as last season, I bought her last season from a good guy, he wasn't even selling it, just had a baby and didn't use it much so I asked if he wanted to sell it, he took very good care of it. So let me ask this would a 21p cause my prob.

 

[Don S]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

No easy answer, here are some possibilities.

 

[WAVENBYE2]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

PROPER operation?? would you start with adjusting the linkage on carb, or throttle linkage????

 

[WAVENBYE2]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

OK Thank you I will start going down the check list, first with the fuel filters,I haven't changed them yetrolleyes Thanks Again Guys, I haven't honestly given it 100% tune up,don't know when the last time it has been properly done, I will definitly use the manuals you gave me DON, I have every thing you gave me under BOAT MANUAL(S) file on PC. I just don't have everything to do it yet($$$) timing light ETC>> She did run great yesterday,sounded beutiful with what I have done with all your help so far. at least I do have a good foundation to work with. At least I was able to take her out yesterday and see how she does, On to the next step.Thanks guys>>>PAT OH, Thanks for the check list too!!

 

[Don S]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

I just don't have everything to do it yet($$$) timing light ETC>>

Funny you should mention that. I just quit my job and gave up being a boat tech. Took 2 full pickup truck loads of tools to get it all my "stuff" home.
To work on a boat properly, you need the proper tools, the knowhow to use them and an OEM service manual. If you are missing one of those items, it will make the job a bit difficult and time consuming. IF you are missing two items in the list. The job will be almost impossible, in many instances. If you lack all three, your chances are slim to none in finding your problems without throwing parts (aka $$$$$) at the problem and hopeing for the best.

 

[WAVENBYE2]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

Well I am working on that Don I really hope you are staying in that field though, You really know your stuff, I hope your going into business for your self, You got a good head on your shoulder, I don't believe you would quit with out a good back up plan..Pat

 

[mcleaves]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

Don's too cranky to work on boats anymore. He's used up everyone in that field.. He needs to move on to something else . Beer making comes to mind!

Get an induction tach on your engine and verify the tach as Don mentioned. I ran into a similar problem and chased my tail for longer than I'll care to admit (although Don will GLADLY let you know how long). Turns out my dash is off by 550 RPMS at WOT. It's exact at idle, so it scales.


M

 

[QC]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

verify the tach as Don mentioned.

Numero uno! And how are you getting your MPH number? 44 is not far off.

 

[WAVENBYE2]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

I am using the mph tach, along with my rpms. tach. on the dash. Ther are times were I thought the mph tach wasn't perfect, I was boating thurs, First time this season. there was a boat in front of me (good size) they were @WOT ,I got up behind them @WOT caught up with them and jumped there wake, boat completely out of water,It was beutiful I was a good 1/4ml ahead of them in no time. What do I need an watt meter to test the tach???

 

[freddyray21]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

get a shop tach and check it against the dash tach. Hook the shop tach up and have a buddy read the numbers on it while you are looking at the dash tach. If you are doing 44 mph my guess is the tach is off.

 

[WAVENBYE2]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

Shop Tach ??? where auto zone,anvanced auto?? Where do I hook it up? Is there a shop rpms tach too? Thanks Pat

 

[bruceb58]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

One thing you should never do is run a prop that was damaged and then "touched up". The pitch gets changed and the balance gets thrown off. For the comparatively few dollars it takes to get it repaired properly, you are gambling bigger dollars with your lower unit. Don't run a damaged prop!

In addition, the fuel savings alone will pay for your prop repair.

 

[freddyray21]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

pick up a tach you can hook to the coil Autozone whatever. That way you can compare tach readings. I know my tach on the dash is a few hundred off from doing this.

 

[WAVENBYE2]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

OK, Thanks guys, I am going to do everything all you guys told me starting with DON S' check list,the prop does vibrate a little(I can feel it in the boat) and a tach meter, Every day I learn more and more THANKS ALL>>>PAT

 

[ricksrster]

Re: 3600rpms?? 44mph. Should be 44-4800rpms

Just to be sure of something, Check the little switch on th back of the tach and make SURE it is set at 6C.