The main lake we go it is at 892' lol.They spin opposite of each other. Not sure how you would "sync" something like that.
@Capt Ron I doubt he is much above 1000 feet.
The main lake we go it is at 892' lol.They spin opposite of each other. Not sure how you would "sync" something like that.
@Capt Ron I doubt he is much above 1000 feet.
The main lake we go it is at 892' lol.
Something I have not seen mentioned and as I do not know the science behind it I could be wrong, but doesn't altitude have something to do with prop selection? I know here in Colorado guys use different props depending on what lake they're going to.
They spin opposite of each other. Not sure how you would "sync" something like that.
@Capt Ron I doubt he is much above 1000 feet.
So I'll be updating this thread here soon, but for now a short update on both boats.
The restored 1996 20ft:
The Big Block 1997 23ft:
- The boat is still at the upholstery shop. Supposedly they are still working on it. The plan is to run it a little bit this season to make sure there are no hidden issues before selling it. Don't want to sell it and plague the new owner with issues. I do have a coworker very interested in it.
I'll be updating this thread with pictures and progress of the maint. that I performed and the results. Headed out this Friday for a week of camping and boating. My dad and brother will be there, so plenty of time to test and tune while on the water to see what we can come up with.
- Got back on Sunday the weekend we picked up the boat. Took it out for a maiden voyage, and was greatly disappointed at the performance. The boat would only go about 43mph. Decided to start checking maint. items to see where it needed improved. Sand in the carb. Spark plugs black and fouled. Plug wires crossed and not timed. Both props bent and out of balance. Lower unit fluid was black. Long story short, the owner lied a lot about recent maint. items done by a local shop. I have spent the last couple of months fixing these issues, while still taking it out on the weekends to test run and enjoy the boat. I've got the boat running a lot smoother, but still about 1k rpms short of the top end that's available.
Hey @Bent77 how much do you know about the Carter AFB carbs?
The boat is now timed and runs pretty good, but once it gets to 3800rpms it just kind of sits there and doesn't rev any higher. Factory specs show it can run as high as 4800rpms. What am I missing?
I rebuilt the carb after I found the sand. I also readjusted the floats as they were way out of speck. Fuel pressure shows a solid 7psi. Plug wires were pulled off and inspected, and reinstalled and double checked. Timed it with a timing light and no longer having hard/long starting issues.
As for props, it has 24P props on it. I know that helps with the hole shot more than top speed, but the fact I am missing 1000rpms tells me there is a little more left in it to get more top end.
Yes correct the dual props do help, but it does seem a little on the slower end to plain out.
The boat was equipped with the Thunderbolt IV system. I installed a new distributor due to the old one being super crusty.
I did not do a prop change. I just had them redone. They were bent and out of balance.
This is the gist of it @ryokenDid a compression test on the cylinders yesterday just to ease my mind.
Odd side:
135
135
130
125
Even side:
135
135
120
140
So I have basically narrowed it down to either fuel or spark. Leaving tomorrow for a week at the lake, so plenty of time to tinker with the carb to see if I can narrow it down.
and make sure your trimming the boat out good, you can lose 500 rpms from that alone....When I first pulled the plugs, a few of them were pretty black. I threw them back in for a test run, and they actually cleaned up a bit during that test run. I do have a fresh set of plugs in, so i'll do a test run and pull the plugs to see what they look like.just some immediate thoughts for you.... plug readings usually tell the story if there's a mill issue, so be checking them often.... make certain you aren't swinging a dead hole.... fresh plug readings will tell you pretty quick.. but you can also set up some slip pliers with a grd wire and pull cap wires while under load to verify.. it'll show quick with Thunderbolt and a carb.... unlike EFI stuff...
another we'll do to eliminate the carb is to take a small squeeze bottle of fuel on a test run, when shes got no more, give her a little squirt and see if it picks up a bit... usually if you are swinging too big a blade, you can almost feel it, the motor will sound smooth and perfect, it just "don't wanna go no more".. we generally cheat and steal another prop from another boat to verify.and make sure your trimming the boat out good, you can lose 500 rpms from that alone....
but we often get boats that are improperly propped at some point... but they are usually inboards..
oh, also... most carbed BB's we come across generally spin 43 to maybe 45, 46 if you are lucky... MPFI stuff is where you see 4600 to 5200 type #'s...
Nah, it would get an 8.1 with motor work before I went that route lol.
That's not even super charged WTF
Correct MR43T'syou're running MR43T 's in that right? plugs are cheap diagnostics, especially those.. be grateful your not running 993's like the 496's at like $18 a plug....![]()
one of the first things I generally do, gives me a fresh slate to see what's going on...
Correct MR43T's

oh, throw in 2 exhaust jobs and an oil pan..... 
That's hilarious, my buddy just asked me about those engines today. I told him I don't know much about them lol. Now I do!only IMO.... NGK's run ok, but don't hold up as well... good luck...
my yr has been nuts... 2 head jobs and 4 repowers in the last 6 wks.. everybody blowing chit up.....oh, throw in 2 exhaust jobs and an oil pan.....
* Ryoken marine tip O' the Day *
don't ever buy something with raw cooled 6.2 mercs....... man, I hate that motor...
That's hilarious, my buddy just asked me about those engines today. I told him I don't know much about them lol. Now I do!
I'll take the 496's all day long... but the worst part about em is the lousy oiling... they run no oil cooler, so the oil gets piss thin... did one last week in a 33 Dancer.. I had done it 10 yrs ago, it was a Jasper.. ingested water from exhaust neglect......
fug that, as an old gearhead, I see #'s that low, I get nervous. 