Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

[MKT210SF]

Hey guys first time boat owner here and new to the forum, I have grown up on boats that my parents owned this is my first boat that I can say is mine she need a little work picked her up for 1100.

Curious what the idle RPM should be? I don't have an owners manual for the boat, my tach is reading a little above 1200 but it could be off shes shaky at idle but nothing abnormal. feels a lot smoother around 1500 rpm. But shouldn't idle be around 800 rpm?

According to a few specs I found the boat weighs between 3100 and 3500lbs the prop that came on it was a 15x17p aluminum she seemed to cruise around 3800-3900 which again seems to high, I'm going to try out a stainless prop I had in my garage which I know is 19p diameter is somewhere in the range of 15".
the speed at cruise was 20mph according to the speedo on the boat which seems fine but still the RPM was a bit high.
hoping the newer stainless prop will help.

I know the inherent problems with the 470 it already has an alternator as as well as 4in heat exchanger, ran her on the water at slow speed temp was solid 130 on cruise 150-155 never got over 160 even after taking her up high I was scared to so I didn't do it for long and I was afraid to over-rev her.

I have a hesitation with my shifter as well it likes to stay in gear unless i wiggle the shifter in the neutral position I would imagine I have to adjust the shifter cable?

So far I put a new impeller and gear oil in the lower unit as precautions the old impeller looked great as did the gear oil.
top end of motor was rebuilt in 06 with newer manifold and the outdrive rebuilt in 05.

all in all the boat is in decent shape when i started to run her harder I noticed a bit of coolant leaking from between the riser and manifold, tightened down the bolts a 1/4 turn or so each and it seemed to stop, any info on this? just a gasket?

Well thats most of my questions/info for now thanks in advance!

Paul.

 

[MKT210SF]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

Yikes I was hoping for a response to work on her today but there is always another I think I have this idle issue sorted but I wanted to check the accuracy of the Tach first.

 

[stonyloam]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

Tach should read between 650 and 700. Pick up a combo tach dwell meter (if you still have a points ignition you will need it) like this: Actron CP7605 Dwell/Tachometer/Voltmeter Analyzer : Amazon.com : Automotive If the boat is new to you you should do a compression check and a cooling system pressure check. That rough idle may indicate a weak cylinder. Pull the plugs and take a look at them. The insulator should be tan or brown, if it is white that may indicate coolant leaking into the combustion chamber. Does sound like the gasket needed tightning, but keep an eye on it and the coolant level. Good luck and welcome to the 470 club:facepalm:

 

[Eric 3.7LX Alpha 1]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

Welcome... I have attached the Tune up chart and a TSB for the 470 regarding timing.

You can check you tach against the dwell meter and some newer timing lights also display RPM's as well.

 

[MKT210SF]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

Thanks guys! found out my Tach was reading about 500 RPM high so my idle is in the range of 700 right now which seems right on!

this also means when i was at 4k on the water crusing it was 3500 rpm which is right where i would want her! now I'm nervous about moving from the 17p prop that was on her to the 19p stainless i just put on.

 

[nola mike]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

What are your rpms at WOT? That's what will tell you if your prop is properly sized...

 

[MKT210SF]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

Quite honestly afraid to open her up, as far as I know the bottom end of this motor was never rebuilt and its 30 years old my plan is to really baby her. but from this spec sheet in 2008 from a test run from a technician it says 4800 rpm. which is a bit high.

I opened her up a little probably took her to 4500 on the tach so about 4000k rpm as my tach when the boat is off is sitting right at 500rpm.

 

[stonyloam]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

About 4200 for WOT is where you want to be. As for the bottom end, this engine was designed specifically for marine use. The engine bottom end (and head) is based on Ford 460 V8 parts (rods and pistons), and the crank is pretty heavy duty, so I would not worry too much about the bottom end as long as you are running good oil (old recommendation: 40 wt or new recommendation: 25 W40) and show decent oil pressure. Above all watch that temperature and change the impeller often. I do mine every other year, yeah I know every year would be better, if I put more hours on I would do it every year LOL!

 

[MKT210SF]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

Yep I read up heavily on the motor especially the weep hole which I am going to have to address soon. I just wisgh my tach read accurately so I didn't have to guess what 4k on my tach meant. Oil press at idle was 20lbs when she was a lower on oil added some and it went to about 45 lbs when running above idle shes around 60 lbs which seems good!

Really for now I jsut want to address the getting stuck in forward and reverse issue which seems to be this interupt switch which I tested and it work killed the motor, it was loose though so I pushed it as far forward on its mounts and tightened it down hopefully that will fix it. if not I will adjust the shift cable.

All I'm hoping now is that rise doesn't leak anymore cause when I did take her up high the rise leaked out a bit of coolant, Hence why i tightened her down.

Also I have to double check the bellows when I put her in again, they dont have cracks or anything well the exhaust one did so I removed it but the others don't look bad, only issues was after an hour or so of running I think I had an extra 2-3 gallons in the boat. It may have come from when I washed the boat and it all came from the bow after I planed off but I am really not sure I looked at the outdrive housing hardcore for a stream of water none at all driveshaft area very dry but I will have to look a little lower next time.

Just worried now about the headaches that are to come I am quite handy when it comes to most things but have not worked on boat myself before mostly cars!

Over all I can't be too worried I picked up the boat mid season in NY for 1,100 sheckles it runs I can't really complain.


Paul.

 

[stonyloam]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

Could be the lower shift cable needs replacing, if your adjustment works you should be OK. Read this: http://forums.iboats.com/mercruiser...nterrupt-system-works-288089.html#post1930449
Here is the deal, you got a 25+ year old boat and motor, you better be handy (LOL), and I don't care what motor you have, if you get it running right and keep up with the maintenance that 470 is as reliable as any engine of that vintage. You know what to look for, keep an eye on that weep hole, do a compression check if you see any changes in performance and keep it cool. If the voltage regulator craps out, do an alternator conversion. The one big advantage you have is when it comes time to winterize. Make sure that your antifreeze is about 50/50 and just pull the transom plug and the aft plug on the heat exchanger and let er drain, I do it right on the ramp when I pull the boat for the winter. That's it, done in 5 min. You can even take it out in November on a nice day, just drain when you pull it out. Like a lot of guys that get 470's, you will read lots of bad stuff and start to worry, but I have had mine since "91" replaced the head gasket, cam seals, 3 starters who knows how many sets of points (the original coil still works BTW) and it has never left me stranded, even when #4 compression was 0, AND #3 was 35. So don't worry about it, enjoy the summer.

 

[MKT210SF]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

Hoping its I don;t need replacement it was last done in 07 and the boat sat for 2 years, but you never know. Alternator conversion was already done on her and I am quite handy so I am not afraid I will be keeping up with the maintenance on.

Gonna do the plugs today the wires seem good still so I will hold off on them for a little.

Cheers,
Paul.

 

[nola mike]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

Doesn't sound like the lower cable. That would cause your engine to stall if the sis is working correctly. Sounds more like an adjustment.

 

[MKT210SF]

Re: Mark Twain Sonic 210 SF Merc 470/Alpha 1 few questions.

Found a leak under my Y-Pipe curious if I can remove it without removing my engine? seems to be a little bit of space to work with, I'm hoping that the Engine can stay.