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View Full Version : Need more holeshot power


lhkrueger
11-30-2012, 11:32 PM
This is an 83 S+S PS 351/240 Hp and the engine performs flawlessly. Beautiful restored old-school boat. Engine is out for winter. Customer wants to add power for multiple person deep water slalom starts. We are familiar with hot-rod engines ( power band 3000 to 7000 rpm) but not marine ( power band 500 to 4000 ). Looking for specific guidelines...comp. ratio, cam lift/duration, flat or roller, head selection, valve size, carburation etc. Cost is not an issue but we don't want experimentaion, rather proven performance. Need to know what actually works real world. Thank you all in advance for your help.

east tx skier
12-01-2012, 12:36 AM
Modern CNC Prop, Heads, Intake, Cam from research cams. Should get at or above 300 hp with plenty of torque. Can go higher, but that always seemed like enough for me.

wheelerd
12-01-2012, 12:46 AM
Assume you are running stock 13 x 13 prop? If so, re-propring may be the cheapest way to go for increased hole shot. You may lose a bit of top end, but with the new CNC'd cupped props, it's not as big a difference as in the old days. Unless you are footing the 40+ mph top end isn't that important anyway.

As for engine mods -- there are quite a few threads here on TT. Recommendations include:
- GT40p heads -- quite readily available on Ebay or elsewhere
- Edelbrock Performer manifold (or equivalent)
- cam - check out www.camresearchcorp.com/ -- they specialize in Fords (JEGS or Summit also have similarly configured cams)

I was planning to do this whole treatment to the engine in my TriStar and had purchased the heads and manifold, but ended up selling the boat before I ever did it. Cam specs I came up with after extensive research were:

int/exh
.450/.480 lift
260/275 duration
112 separation
1800-4800 power range

thatsmrmastercraft
12-01-2012, 11:25 AM
Have a conversation with Eric at OJ Props. He has been around the block once or twice and will give you some great prop recommendations. 865-458-5205 http://www.ojprops.com/

I agree with east tx skier, getting in the area of 300-325 hp with the right prop will do exactly what you want.

lhkrueger
12-02-2012, 12:46 AM
Thanks all. Is powerslot so has big prop 14/18 with gear reduction. Cam specs are great and 300-325 hp with gobs of low range torque is the prime objective. THANKS

thatsmrmastercraft
12-02-2012, 01:07 AM
Please keep us in the loop on how this turns out.

northof52
12-02-2012, 06:25 PM
.....if you we're only to recommend one of those upgrades.....which would it be? I have a'90 prostar...and have been tossing the idea of the head upgrade

j.mccreight@hotmail.com
12-02-2012, 07:00 PM
.....if you we're only to recommend one of those upgrades.....which would it be? I have a'90 prostar...and have been tossing the idea of the head upgrade

Cylinder heads alone are not worth doing.

I did all these engine mods (1989 TS190 351W 1:1) over the summer and from MY experience the best single mod for your money will be an acme cnc prop, you will gain hole shot and top end with just a prop change. While I gained about 400 rpm from the top end kit (aftermarket heads, roller rockers, intake manifold and camshaft) and had very good hole shot but was not any faster with the original OJ legend 13x13 4-blade. I was left feeling there was still more on the table, after the prop change, Acme #541 13x12 cnc 3-blade it had even more hole shot and was even faster (47mph@5000rpm)

east tx skier
12-02-2012, 08:03 PM
Cylinder heads alone are not worth doing.

I did all these engine mods (1989 TS190 351W 1:1) over the summer and from MY experience the best single mod for your money will be an acme cnc prop, you will gain hole shot and top end with just a prop change. While I gained about 400 rpm from the top end kit (aftermarket heads, roller rockers, intake manifold and camshaft) and had very good hole shot but was not any faster with the original OJ legend 13x13 4-blade. I was left feeling there was still more on the table, after the prop change, Acme #541 13x12 cnc 3-blade it had even more hole shot and was even faster (47mph@5000rpm)

Agree 100%. The intake and heads are a great combo upgrade after the prop. But since you already have gear reduction, you already have plenty of grunt out of the hole.

thatsmrmastercraft
12-02-2012, 09:49 PM
Also agree that if one change is to be made it should be a new prop. I would also look at the ignition system and upgrade to electronic (if it isn't already) and confirm that you are getting all the advance you are supposed to. I would also go through the carb as well.

j.mccreight@hotmail.com
12-02-2012, 10:12 PM
Also agree that if one change is to be made it should be a new prop. I would also look at the ignition system and upgrade to electronic (if it isn't already) and confirm that you are getting all the advance you are supposed to. I would also go through the carb as well.

I wouldn't worry to much with total timing advance. I would just ensure that its working as designed. On my original point distributor with EI it was 29 @ 3000 rpm and I "thought" it needed more timing so I bought the high dollar adjustable unilite marine distributor ($350) and set it at 36 and did some tuning and I actually picked up 100 rpm by bringing the timing back to 29. Oh well at least I have a good spare...

thatsmrmastercraft
12-02-2012, 10:16 PM
I wouldn't worry to much with total timing advance. I would just ensure that its working as designed. On my original point distributor with EI it was 29 @ 3000 rpm and I "thought" it needed more timing so I bought the high dollar adjustable unilite marine distributor ($350) and set it at 36 and did some tuning and I actually picked up 100 rpm by bringing the timing back to 29. Oh well at least I have a good spare...

I guess I could have been more clear by saying to check for proper distributor operation, as it is going on 30 years old and probably untouched.

northof52
12-05-2012, 09:11 PM
....so acme over oj.....

thatsmrmastercraft
12-05-2012, 10:57 PM
....so acme over oj.....

Eric from OJ Props is an active member here, so many of us choose to send business his way. I have no experience with Acme (other than watching Road Runner cartoons) and people seem to be plenty happy with quality and service from both companies.

DooSPX
12-10-2012, 02:11 PM
Personally, I choose OJ Props, Eric has been extremely helpful and just a great guy to talk to. I would call him up and see what he recommends. Their number is in my signature.

So, as said here before, go with a new prop first. If you feel you still need more, then start looking into engine mods.

east tx skier
12-10-2012, 03:25 PM
....so acme over oj.....

If they are both running a 30 day try and send it back if you don't like it program like they used to, you should try one from each. If you don't, you'll never know if the prop you got was the best choice for your application. It matters not a bit what my opinion is versus anyone else's on here about prop brand. And I say that as one of the people on here who has done a critical comparison test between the Acme 541 and comparable OJ XMP 13x12.

Prop Comparison (www.tylerskiclub.com/proptest.pdf)

Note: These are not the props applicable to your boat. But it will give you an idea of how different two similarly sized props can be.

EJ OJPROP
12-10-2012, 03:53 PM
Give me a call and I can get you a prop to try.

Kevin 89MC
12-10-2012, 05:41 PM
FWIW, I did upgrade only my heads, out of necessity. Cracked one a few years back, posted the whole ordeal on here. Still running old school 4 blade prop, original intake. Didn't have the cash to upgrade either when doing the heads, plus I was curious to see what the increase would be for heads alone. Found some GT40 heads in a junkyard for cheap, got them cleaned up and installed, and gained about 4-5 mph of top end speed. Boat has quite a bit more oomph. Not sure how much HP, but it has to be significant to gain 4-5 mph. Had to re-calibrate all the pefect pass slalom speeds in the course, as expected. I do agree that prop changes can be significant as well, and if I ever get the cash, or have a need for more speed, that will be my next upgrade.
Kevin