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whats wrong with my convincor?

D

daigostang

Member
hi everyone this is my first post, i just got my first checkmate, it is a 1988 251 convincor, 454 magnum carb motor, it has an edelbrock torker 2 intake and holley 750 carb other than that it is completely stock. The previous owner told me it runs 65 on gps, i took it out for the first time yesterday trimmed out with just me on the boat with only a 1/4 tank of fuel it only went 57 on my gps, the prop is a dinged up quicksilver 23p. seeing as this is my first checkmate im not sure what it is supposed to run, it was turning 5300 rpms and i still had a little more trim to go is this normal or do i need to fix somthing? thanks!
 
Did it run 65 when you water tested it? If you didn't water test:shakehead: then it might have run that when the motor was fresh and the prop wasn't bad. Water conditions on this hull play a big part. I don't think he was not being true but theres alot of factors and seat time to see 65. It is possible but on the high side.

:welcome:Good luck!
 
actually i never water tested the boat. just sort of an impulse buy. when i did get the boat home i put it into the water ( lake ontario) completly flat windless day no chop to the water. i figured the prop was going to be an issue seeing as its got a bent blade, and some other chips,
 
Your gonna run slow on flat water. That hull likes a 1-2ft chop. The props not helping. If you get a prop try a 24 bravo 1. they work good on this hull and will help bbring down your rpms a little.
 
My 92 251 when it had a 502 mag in it on a good day with good water conditions it would do 65mph. I also spun a 3 blade 23p prop at 5100RPM. Like the previous post water conditions plays a huge role on how this boat runs, likes 1' + chop is usually when I get my best numbers. And it does take some seat time to find out where to trim her out to.
 
well its good knowing my boat is roughly where it should be, since my prop is shot and needs a new one, any suggestions? i was thinking a 23p mirage plus labb finish, does that sound about right? or maybe a 25p?
 
also, i noticed my intake manifold has the carb sitting off to an angle is this normal? i did some reading up on the intake and apparently its mostly used on older corvetts with hood clearance problems, i was thinking about going with the power package combo from cp performance its a hp500 style intake and holley 800cfm carb would this be a good deal or a waste of money?
 
daigostang said:
also, i noticed my intake manifold has the carb sitting off to an angle is this normal? i did some reading up on the intake and apparently its mostly used on older corvetts with hood clearance problems, i was thinking about going with the power package combo from cp performance its a hp500 style intake and holley 800cfm carb would this be a good deal or a waste of money?
Click to expand...

May need a picture to see what you mean about sitting on an angle, or more explaining.
I will say that a single plenum Torker 2 intake is not the best intake for a all stock motor. I think, if you look it up, you will find it's designed for a RPM range of something like 2500-6500rpm. You would be better with something that provides max power in the 1500-5000rpm range if your going to leave that motor mostly stock.
I don't think you would see any benifit changing the carb unless there is something wrong with it.
 
Don't bother with the lab finish. 23 mirage or 24 bravo props. A link to the cp stuff would help. Don't know your budget but some headers and m3 procharger will be badazz. Tell my wife thats what I'm getting for christmas. lol
 
with my 251, 24 bravo best all around, but a 23 mirage + will run about 2 mph faster on top end...all the planets better be strait to run 65 with a 454 unless making close 450hp
 
thanks for all of the info guys, i started out a week ago with a $4000 dollar budget to work on this boat over the winter but i decided to get the interior re done before any motor work so 2300 of that money went poof. so now i have between $1500-$1700 to tinker with the motor, i was thinking
new prop, new intake, and some emi exhaust?
 
keep your eyes open for used intake and carb, i bought an hp500 carb and intake for my 502 for 250 bucks. it was in good shape, i spent some money rebuilding the carb but still a good budget. check out boatfreaks.org to find some parts now and then.
 
would buying a set of dana headers be a good investment? i was thinking the headers and the right prop and i would be set for this season, maybe do a bigger motor next winter
 
If the motor is a real 454 Magnum, the internals are all forged steel and the motor can be super charged or turbo charged if you're willing to spend the $$$. The 251 is a big boat..with the right prop you shoud be right at 60 MPH GPS turning 5200 rpm and 365/385 hp. I would be looking for a good Bravo One prop, stainless marine headers, intake/carb off of an HP 500 carb motor and a drive shower.
 
I am happy all of the other convincor owners chimed in, at first i was worried something could be wrong, now i see the boat is right where it should be and i am relieved. i cant believe the ride quality of this boat it is amazing compared to my old baja and pachanga. As for headers i have narrowed it down to EMI thunders, Dana Marine, Or stainless marine manifolds. anyone care to chime in and make that choice for me?
 
I have the EMI Thunder aluminum manifolds with the long tail stainless risers. They are good looking, sound great, flow some good power, and with the long tails I am able to run a dry header cam with no reversion issues. I also have an oxygen sensor welded into my tails......works great for tuning.
 
i have factory silent choice, how do the tails work with that do i need special ones? i have to keep the silent choice or get another season of tickets from the coast guard and sheriff leaving the dock. once im on the lake no one cares but comming out of the river is another story.
 
You wouldnt be able to use the long tails with the silent choice. You would use the standard risers or the short stainless ones. Should have no issues with keeping the choice. Mine is quite loud with the new cam now and I am going to add switchable mufflers to my tips to mitigate the problem with jonny rotten law that you described.....they are gettin bad around here.
 
i had reversion issues with my emis and silent choice, also with long risers....may have been the cam.
however, a friends 502 mag with the emis and aluminum risers with 02 bungs welded in would revert water with the stock cam. we noticed it when having the bungs open and silent choice off (above water exhaust). we would actually have water spitting out of the hole for the 02, now switch it to below water (quiet) and the water would stop spitting. not sure what was going on there!
the thunders are popular and seem to be fine in many applications. I personally wouldnt run them again based on the problems i have seen so far. IMHO
 
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