90 Prostar 351w performance question

[Pro351]

Hope all is well everyone. So I recently purchased my first boat this past July. First time boat owner. I'm hooked. Love it. I have posted pictures of it in prior threads.

Anyways... the previous owner pulled the engine, had it bored .30 over, new pistons, rings and cam. The rebuild has about 40 hours on it. Just before the winterizing process, I heard some lifter/rocker arm noise and realized he installed another flat tappet cam with solid lifters... so a re-torque of the rocker arms is common after a rebuild. The issue I have is, after all that work of rebuilding the bottom end, he kept it a solid motor and also reinstalled the stock heads, intake and carb. The bottom end is new, with a bigger cam, yet the top end isn't able to breathe anymore than a stock 351. I'm thinking about converting it to a roller motor, along with high performance heads, new intake and carb. If I decide to do this work... what would I see for performance gains? Acceleration? Top speed gain, etc? I would assume it would be about a 30-40hp increase. Would all of this time and money be worth it? I used to be a Ford technician, so the labor would be free. I know what all this would mean in a car as far as gains, but never owning a boat before, I'm not sure what to expect on the water.

Any and all recommendations are appreciated. Thanks.

[waterlogged882]

Hope all is well everyone. So I recently purchased my first boat this past July. First time boat owner. I'm hooked. Love it. I have posted pictures of it in prior threads.

Anyways... the previous owner pulled the engine, had it bored .30 over, new pistons, rings and cam. The rebuild has about 40 hours on it. Just before the winterizing process, I heard some lifter/rocker arm noise and realized he installed another flat tappet cam with solid lifters... so a re-torque of the rocker arms is common after a rebuild. The issue I have is, after all that work of rebuilding the bottom end, he kept it a solid motor and also reinstalled the stock heads, intake and carb. The bottom end is new, with a bigger cam, yet the top end isn't able to breathe anymore than a stock 351. I'm thinking about converting it to a roller motor, along with high performance heads, new intake and carb. If I decide to do this work... what would I see for performance gains? Acceleration? Top speed gain, etc? I would assume it would be about a 30-40hp increase. Would all of this time and money be worth it? I used to be a Ford technician, so the labor would be free. I know what all this would mean in a car as far as gains, but never owning a boat before, I'm not sure what to expect on the water.

Any and all recommendations are appreciated. Thanks.

Here's my take on this...there are so many options and others' opinions:

GT-40P heads from a 302 engine with TFS spring kit. They are out there...built to specs.
Edelbrock Performer intake for the 351W
New Holley 4160 600 cfm marine carburetor
New plug wires
New high output coil
New electronic ignition module

As for gain? Because you have an upgraded bottom end and with the above upgrades, my throttle-hand guess is 30-40 HP. Without the bottom end build and only the top end add-ons (very common) there is not much gain at all, really not worth the money for maybe 10 HP gain, if that.

For the above I have these upgrades on a 351W with an upgraded bottom. I like it but a stock engine will tow a skier just as well with the correct prop... hole and top end. The gain for me is not so much the HP but the throttle response capability when bare footing. One leads to the other but I am not about top end speed aside from a bare foot run in the lower 40s.

An Acme 541 12x12 prop will give you all you need on a stock 285 HP engine as well as the upgrade.

Proactively, (but not mandatory) new exhaust manifolds, new risers, and new exhaust hoses.

On the water, you'll get a stronger engine response throughout the RPM range with the Acme prop. Noticeable but again, skiing is skiing so top end results are not my appeal. Your engine RPM will stay within 4200 - 4800. Stock 1:1 is right at 4400 max.

US $0.02

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[h_2_o]

one thing to think about is if you are looking for a boat with top speed by doing this do yourself a favor, sell it to someone who will use it and get a gofast boat instead. I'm not trying to talk you out of anything just way to many people hear 351 windsor big v8 and think MPH. these boats are primarily tug boats first and foremost. then they do other things

[d2jp]

Would all of this time and money be worth it? If you are a skier, and use boat as a slalom tug, IMO it's not worth it.
But considering it's the "off season" and if you have extra time and money and want to mess with your boat (as usual) I agree with waterlogged's assessement on what gain you might see.
I also 100% agree that if you're not running an Acme 541 prop, that is the best bang-for-the-buck performance upgrade you can make.

[Pro351]

Here's my take on this...there are so many options and others' opinions:

GT-40P heads from a 302 engine with TFS spring kit. They are out there...built to specs.
Edelbrock Performer intake for the 351W
New Holley 4160 600 cfm marine carburetor
New plug wires
New high output coil
New electronic ignition module

As for gain? Because you have an upgraded bottom end and with the above upgrades, my throttle-hand guess is 30-40 HP. Without the bottom end build and only the top end add-ons (very common) there is not much gain at all, really not worth the money for maybe 10 HP gain, if that.

For the above I have these upgrades on a 351W with an upgraded bottom. I like it but a stock engine will tow a skier just as well with the correct prop... hole and top end. The gain for me is not so much the HP but the throttle response capability when bare footing. One leads to the other but I am not about top end speed aside from a bare foot run in the lower 40s.

An Acme 541 12x12 prop will give you all you need on a stock 285 HP engine as well as the upgrade.

Proactively, (but not mandatory) new exhaust manifolds, new risers, and new exhaust hoses.

On the water, you'll get a stronger engine response throughout the RPM range with the Acme prop. Noticeable but again, skiing is skiing so top end results are not my appeal. Your engine RPM will stay within 4200 - 4800. Stock 1:1 is right at 4400 max.

US $0.02

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Just to clarify... your boat has all the upgrades which you stated above? So with those upgrades and the 541 prop, what is your top speed? And is there a noticeable difference in acceleration and drivability?
I have no issue spending the money and doing the work if the gains are obvious. I just wanted some incite from someone who has first hand experience.... Basically... is the juice worth the squeeze?

I've looked into the GT40P heads. I've very familiar with them, as I've rebuild many 5.0's. Also I looked into high performance 351 heads.

I don't ski, but I have friends that do. I just like cruising around. I enjoy the acceleration more than top speed, but wouldn't mind getting another couple miles per hour out of her. I actually just did plugs, wires, cap, rotor, and coil a few weeks ago. So good to go there. Appreciate your expertise.

[Pro351]

one thing to think about is if you are looking for a boat with top speed by doing this do yourself a favor, sell it to someone who will use it and get a gofast boat instead. I'm not trying to talk you out of anything just way to many people hear 351 windsor big v8 and think MPH. these boats are primarily tug boats first and foremost. then they do other things

I love these boats. And I bought it knowing it wouldn't run 50mph. I don't need a go fast boat. I actually like the acceleration more than the speed... but like I stated previously, I would like another 2 or 3 miles per hour. My boat does 42mph (GPS verified) whether it's just me or or I have 6 people on the boat. The boat performs well... my train of thought is the bottom end is ready to go... and the top end is holding her back, so with a full day's work, she could be a different machine when back on the water. Plus I just had it wrapped in vinyl so she's looking good.

I've been asked many times why I like my boat, because I don't ski, fish or do anything water related sports. I tell them I enjoy cruising on the water... and more importantly, it allows me to get away from people and the craziness of daily life. People can't bother me on the water. It has become my outlet. My peace of mind. If that makes sense....

[Pro351]

Would all of this time and money be worth it? If you are a skier, and use boat as a slalom tug, IMO it's not worth it.
But considering it's the "off season" and if you have extra time and money and want to mess with your boat (as usual) I agree with waterlogged's assessement on what gain you might see.
I also 100% agree that if you're not running an Acme 541 prop, that is the best bang-for-the-buck performance upgrade you can make.

Not a skier... and actually right now is a good time financially for me to do the upgrades. Plus I enjoy working on it. It's become my new hobby. Appreciate your advice.

[waterlogged882]

Just to clarify... your boat has all the upgrades which you stated above? So with those upgrades and the 541 prop, what is your top speed? And is there a noticeable difference in acceleration and drivability?
I have no issue spending the money and doing the work if the gains are obvious. I just wanted some incite from someone who has first hand experience.... Basically... is the juice worth the squeeze?

I've looked into the GT40P heads. I've very familiar with them, as I've rebuild many 5.0's. Also I looked into high performance 351 heads.

I don't ski, but I have friends that do. I just like cruising around. I enjoy the acceleration more than top speed, but wouldn't mind getting another couple miles per hour out of her. I actually just did plugs, wires, cap, rotor, and coil a few weeks ago. So good to go there. Appreciate your expertise.

When I bought this boat from a dud (not dude) in FL (in November) we ran it in his driveway on a hose. All good. Fast forward, I worked on it all winter of that year and into Spring of the following year. Fired it up and saw a small droplet leak. Turned out that the sorry JB Weld material (that should be outlawed -- >SPIT<) was leaking on one of the heads (which was not disclosed at sale). I took the engine down and found it had cam/ bore, etc. Then I put new heads on it because of the aforementioned. He had sold me an engine with false information but it was recoverable so at that time I knew what was what about the engine. I had new 40P heads built to spec. (roller) so at that point (and now) I know what the engine is made of. I am on the verge of lifting the engine again to put in new seals and rebuild the transmission. This is a good engine at 450 hours but at this time I am going to re-do everything while the engine is out and refresh the overall components. I have everything new on it now as far as peripherals but it has a tiny rear seal leak, Can't stand it.

To your question; I have had the HO engine stock in another boat so that is the basis of my comparison. There is a noticeable difference in the engine throttle response as I stated earlier. It still runs right at 45 MPH and 4400 RPM with the 1:1 transmission and Acme 541. I might see a 46 on the digital GPS readout on my PerfectPass every now and then. Drive-ability not so much difference aside from power in a tight turn to push the boat through the turn but my 190 hull handles like a dream in all situations. I notice mostly the push through a turn on the 205 hulls. They require throttle to complete a tight turn.

If I were to do it from stock, it's just not worth the money for what small gain you get. I bought mine this way (unbeknownst at the time) and to do it again...? It would have to be a situation where that was the only resolution to a bad engine (the rebuild). As for an upgrade for fun?...probably not. I just don't see it from my point of view. As for an addiction to the hobby...? Sure thing. Engines look pretty, run great, top performing components, etc. but the daily use will not change much. I do like the HP for an immediate throttle response when I foot. As to slalom skiing (at 36 MPH for me), plenty of time to get up to speed so not so critical for the slalom skier unless you are in a short tight-as$ cove to get lined up for entry (and exit turns) with a course (been there too).

Your call on the final answer. Stock is right there with an upgraded engine as far as end-use deliverable. Aside from personal satisfaction and recreation, no one will know but you.

By the time you have the machine work done, new parts, etc, you can buy a nice new trailer and take the wife out to dinner.

Best on the results but if it isn't broken.... drive it like you stole it and enjoy. Invest that $5K in your future savings plan.

US $0.02
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[Pro351]

When I bought this boat from a dud (not dude) in FL (in November) we ran it in his driveway on a hose. All good. Fast forward, I worked on it all winter of that year and into Spring of the following year. Fired it up and saw a small droplet leak. Turned out that the sorry JB Weld material (that should be outlawed -- >SPIT<) was leaking on one of the heads (which was not disclosed at sale). I took the engine down and found it had cam/ bore, etc. Then I put new heads on it because of the aforementioned. He had sold me an engine with false information but it was recoverable so at that time I knew what was what about the engine. I had new 40P heads built to spec. (roller) so at that point (and now) I know what the engine is made of. I am on the verge of lifting the engine again to put in new seals and rebuild the transmission. This is a good engine at 450 hours but at this time I am going to re-do everything while the engine is out and refresh the overall components. I have everything new on it now as far as peripherals but it has a tiny rear seal leak, Can't stand it.

To your question; I have had the HO engine stock in another boat so that is the basis of my comparison. There is a noticeable difference in the engine throttle response as I stated earlier. It still runs right at 45 MPH and 4400 RPM with the 1:1 transmission and Acme 541. I might see a 46 on the digital GPS readout on my PerfectPass every now and then. Drive-ability not so much difference aside from power in a tight turn to push the boat through the turn but my 190 hull handles like a dream in all situations. I notice mostly the push through a turn on the 205 hulls. They require throttle to complete a tight turn.

If I were to do it from stock, it's just not worth the money for what small gain you get. I bought mine this way (unbeknownst at the time) and to do it again...? It would have to be a situation where that was the only resolution to a bad engine (the rebuild). As for an upgrade for fun?...probably not. I just don't see it from my point of view. As for an addiction to the hobby...? Sure thing. Engines look pretty, run great, top performing components, etc. but the daily use will not change much. I do like the HP for an immediate throttle response when I foot. As to slalom skiing (at 36 MPH for me), plenty of time to get up to speed so not so critical for the slalom skier unless you are in a short tight-as$ cove to get lined up for entry (and exit turns) with a course (been there too).

Your call on the final answer. Stock is right there with an upgraded engine as far as end-use deliverable. Aside from personal satisfaction and recreation, no one will know but you.

By the time you have the machine work done, new parts, etc, you can buy a nice new trailer and take the wife out to dinner.

Best on the results but if it isn't broken.... drive it like you stole it and enjoy. Invest that $5K in your future savings plan.

US $0.02
.

Appreciate your advice. Very helpful. Sorry to hear about the JB weld... that's awful. As a former Ford Technician, I hate stuff like that.

You make some solid points on why or why not to install the upgrades. But the longer I own this boat,, the more I enjoy it. It reminds me of a late 80's early 90's muscle car. I was actually amazed at how many compliments I got on the water (before it was wrapped in vinyl). There is a true appreciation for these machines.

With that being said... I'm leaning towards doing everything. Heads, cam, roller lifters, roller rockers, intake, carburetor and prop. Although I'm almost positive I have the 1:5 powerslot. I need to recheck the tag. Will the 541 still work well with the 1:5 trans? The reason I'm leaning this way is because of what you mentioned, this boat has become my hobby, plus I can do everything myself. Not to mention I love anything that accelerates fast. Top speed I'm ok with 45pmh. Because getting there fast is the adrenaline rush. And probably most importantly, I'm in a good financial situation right now. So now is ideal to sink a few bucks into the engine. I didn't didn't buy this boat as an investment... so I'm not looking to get my money back if I sell it. I enjoy it very much and it makes me happy. And that to me is priceless.

[waterlogged882]

Appreciate your advice. Very helpful. Sorry to hear about the JB weld... that's awful. As a former Ford Technician, I hate stuff like that.

All part of it.

You make some solid points on why or why not to install the upgrades. But the longer I own this boat,, the more I enjoy it. It reminds me of a late 80's early 90's muscle car. I was actually amazed at how many compliments I got on the water (before it was wrapped in vinyl). There is a true appreciation for these machines.

With that being said... I'm leaning towards doing everything. Heads, cam, roller lifters, roller rockers, intake, carburetor and prop. Although I'm almost positive I have the 1:5 powerslot. I need to recheck the tag. Will the 541 still work well with the 1:5 trans?

No. Your powerslot will have a 1-1/8" diameter drive shaft, therefore the 541 (model number) will not work. And I also presume your 1-1/8" shaft is keyed and not spline on your year make.

Within the Acme brand there are two props you should consider:
1) Acme 1749 - 3 blade 13.5" x 17.5" with a cup of 0.150" left hand rotation (harder bite in the hole with a tiny bit less top end performance)
2) Acme 801 - 3 blade 13.5" x 17.5" with a cup of 0.105" left hand rotation (softer bite in the hole but top end preference)

I personally prefer the #2 option. I don't think there is a hill of beans of difference in the two for me as a recreational boater at this point in time; 36 MPH and 42 MPH is all I am after. You make the final call.

The reason I'm leaning this way is because of what you mentioned, this boat has become my hobby, plus I can do everything myself. Not to mention I love anything that accelerates fast. Top speed I'm ok with 45pmh. Because getting there fast is the adrenaline rush. And probably most importantly, I'm in a good financial situation right now. So now is ideal to sink a few bucks into the engine. I didn't didn't buy this boat as an investment... so I'm not looking to get my money back if I sell it. I enjoy it very much and it makes me happy. And that to me is priceless.

Agree... your ball, your call...you do know these things are a never ending money pit...lol...

Glad to hear you have a passion and a direction. I say go for it all out. Best on the build. Keep this thread updated please.

Your powerslot will have a slight variation of RPM range but still comparable by ratio of the aforementioned specs for the 1:1. You'll see a little higher RPM and maybe am extra MPH climb.

You will love the PerfectPass.

.

[88 PS190]

Should still be a keyed shaft - MC used keyed shafts I think till around 2003?

[Pro351]

Glad to hear you have a passion and a direction. I say go for it all out. Best on the build. Keep this thread updated please.

Your powerslot will have a slight variation of RPM range but still comparable by ratio of the aforementioned specs for the 1:1. You'll see a little higher RPM and maybe am extra MPH climb.

You will love the PerfectPass.

.

Great to know. I will look into the Acme 801. And will for sure post updates as I progress.

[Pro351]

Should still be a keyed shaft - MC used keyed shafts I think till around 2003?

I honestly haven't looked at it closely... but I'm pretty sure it's keyed.

[h_2_o]

unless someone put an aftermarket splined shaft of it then yes it should be keyed.