hey guys looking for some advice here. i bundled both of these together motor BBC and SBC because im having the same issue on both style motors in diff boats that are about the same.


20' welcraft nova has rebuild SBC .30 over but everything else is stock expect the cam. 4 barrel carb.regualr exhaust manifolds this motor came this way from when i bought it.

cam number is ( comp cam 12-236-3) i will explain my issue in a second


23' welcraft nova has BBC gen 6 this motor is worked. stroked, .30 piston 10:1, factory heads( will get replaced in time), 4 barrel carb, EMT exhaust manifolds, had a xtreme marine cam flat tappet SK11-232-3 in it before then motor lost oil pressure and blew up so when i rebuilt this set up got talked into a diff cam ( hp500 PN: 169611 its a mhp-300 roller) i can post specs on it. gotta get them from my notes out in the pole barn.


to start i hate the cam in the BBC now. loved the old one.



reason i put both boats and motors in same post is because i now have the same issue between both boats so its all related.


when i first bought the 20' it ran good. i had issue with 21p 3 bad prop fighting me out of the water with more then 2 people. with 2 my rpms wot are about 5200 little high meaning i need bigger prop. I've gone to 23p 3 blade with 2 people fights me slightly getting out of the water rpms are 4800 and runs good. BUT if i have any wind, tide or anything along those lines i can't get it up out of the water with the 23p. so if i have more then 2 people i got to 19p gets up but rpms are high. from day 1 getting the boat I've said the cam isn't right but wasn't 100% sure. I've reached out and everyone don't really give me good answers. they all tell me that the prop pitch is to high or small. i don't think they really understand my issue. I've even reached out and found people with the same boat as me( but i never knew the cam i had in the boat until this past weekend when i pulled the motor to compare) and they all use 21p 3 blade with no issues. again this boat has SBC.


when i got the 23' nova had stroked BBC same set up i just redid it to but had xtreme marine cam. boat has 24p 4 blade would get out the water 3-4 people no problem and ran good( rpms would be about 5200 didn't get that far to try bigger props. don't really care to much yet) boat would run 75 and sound great. till the day i los oil pressure cause it had a high volume oil pump with regular factory pan. motor blew up took out the flat tappet cam and everything else. so then i got new block built a stroked BBC again but this time i reached out and was told the cam i have is to small for my set up go bigger, so i got roller cam this time and went bigger to cam i was suggested. the hp 500. i hate it. not sure if the cam is my problem but that the only thing diff from set up to set up. motor don't sound as good with the lope like the other cam, fights me out of the water i even went to a 21 p prop and runs like ****. only gets to about 4200 rpm with tells me the prop is to big, and im only doing 45ish. so i think the cam is the problem.


with that being said brings me to the 20' nova the cam isn't right. so im looking for suggestion on both boats. 23' nova clearly is the worked set up. the 20 isn't. i just want it to run right. let me know what you guys come up with



23' nova cam specs

comp cam i had rpm rang is 1-5k

comp cam that i found close to the flat tappet but its roller rpm rang is 1600-5400

cam i have in it right now rpm range is 2500-6000


i will do more reading. just trying to get some input maybe someone had this issue before and changed cam to something better. or maybe someone out there has the same set up or close with diff cam and is happy. i am not with either boats.


thanks guys. if this is in the wrong section i am sorry. i don't know my way fully around the page. im trying.

Nothing wrong with running WOT at higher rpm. Going above 5500 unless required or 6000 as my no crossing line...unless serious race level requirement.

The engines need to be setup for these rpm. SBV will take 5500 no problem, as long as the valvetrain is (springs) are compatible.

Mercruiser gives low rpm max specs from the small cams and power bands with how it sets up the engines.

If you overprop with larger cams...the engine may not produce the required HP to get past a certain rpm. Thr load and HP prodiced equalize.

my rpms being higher like that isn't so much my concern. i know to stay under my limits. im always watching out for it. its more the not getting out of water and fighting me. both motors do it. and with the 23' now with the diff cam it runs worse then it did with the other cam. that's why im comparing both motor and cams, im having the same issue with both motors when the BBC i didn't have the issue till this new cam. im thinking about going with the comp cam that matches what i had before was flat tappet to a roller. the rpm rang in the roller is 1600 vs the flat tappet is 1000. guess its not that bad. first cam flat tappet was 1000 and the cam i got now is 2500 so that's 1500 diff. think im gonna go with the 1600 rpm rang cam for the bbc


now the sbc not sure if i should go smaller cam. it fights me out of the water and i hate it. the 23' gets up and goes. the 20' with the sb shouldn't fight me this much. id like if someone else who has this same cam as me would chim in. or same motor and diff cam that they like.

my rpms being higher like that isn't so much my concern. i know to stay under my limits. im always watching out for it. its more the not getting out of water and fighting me. both motors do it. and with the 23' now with the diff cam it runs worse then it did with the other cam. that's why im comparing both motor and cams, im having the same issue with both motors when the BBC i didn't have the issue till this new cam. im thinking about going with the comp cam that matches what i had before was flat tappet to a roller. the rpm rang in the roller is 1600 vs the flat tappet is 1000. guess its not that bad. first cam flat tappet was 1000 and the cam i got now is 2500 so that's 1500 diff. think im gonna go with the 1600 rpm rang cam for the bbc

now the sbc not sure if i should go smaller cam. it fights me out of the water and i hate it. the 23' gets up and goes. the 20' with the sb shouldn't fight me this much. id like if someone else who has this same cam as me would chim in. or same motor and diff cam that they like.

Just curious if either of your replacement cams were degreed when installed.

This is exactly what I was thinking. Sounds like someone just lined up the dots, more or less, and bolted it in. I really don't think the cams are the problem. I think tuning is needed and maybe opening those engines up and checking the degree install on the cams. Going over the lash, setting timing properly, etc. can make a heck of a difference.

Where abouts is the OP located. May be able to recommend a competent person that would be willing to help out.