Heavy Boat, need advice

[hblair]

Hi guys, here's the pertinent info for my situation here. Any help would be appreciated...

1) Boat is slow to plane, have to roll onto throttle. I want more hole shot for sure.
2) Current prop is a well worn michigan wheel 217 cup aluminum
3) Current prop 15" diameter 17 pitch
4) Wide open throttle 4700 RPM at 32 mph (keep in mind, prop is well worn, one blade has 1/2" of tip bent
5) Engine is a ford 302 producing 280-300hp, out drive is an 898 (chev unit), which I believe has a 1.65 to 1 ratio
6) Boat is a 1988 Glasstream Seaquest 26'. I'm not exactly sure about the weight, but it is heavy.

I was thinking of going to a 15 pitch prop, but am having a hard time finding what I need.

 

[Lyle29464]

Re: Heavy Boat, need advice

Hate to say it but I think you doing about all it will do. Of course you need a new prop but I dont see anything you can change. If you do a 15 prop you will have a better low end but the 302 does not like 5000 rpm.

 

[Flysfloatsor]

Re: Heavy Boat, need advice

Ive never heard of a naturally asperated 302 making 280-300 hp. Stock your between 180 and 200 hp at the flywheel.

That being the case, if its pushing 26' of anything in water to 32mph is not just good, its great!

 

[hblair]

Re: Heavy Boat, need advice

My 302 isn't stock. 300 hp out of a 302 is not a big deal. Hot rodders get as much as 500hp at which point the blocks like to break. Before I bent the prop I was getting 35mph+ out of it. I think I'm gonna order a 15 pitch prop. I found some on here for sale. I figure this damaged prop has some big time slip at top speed. I wouldn't be surprised if a clean 15 pitch prop would push the boat 30mph+

 

[Mac525]

Re: Heavy Boat, need advice

5000 rpm is nothing for a 302 niether is 300hp they came stock in 71 with 190 on a points ignition. I have one questions ,1 what is the red line of your 302

 

[QC]

Re: Heavy Boat, need advice

Careful about comparing hot rod performance to marine. Do not assume they are the same, they are not. The cams used for street performance will often cause reversion in boats. Do a search in the I/O sections. VERY IMPORTANT to understand

To the OP, why is hole shot so important in a cruiser? If it is, then I understand your plan, but it almost sounds good with the 17. Why not add trim tabs to improve planing sped? That's why you see them on larger boats. And why "roll onto throttle"? Hammer it.

 

[rrhodes]

Re: Heavy Boat, need advice

You said your motor is not stock but you haven't given us any idea of what has been done to it. The 15p prop is going to over-rev your motor and you said you were getting 35mph before so replacing your current beat up prop with a better quality and maybe even a stainless prop will get you back to 35-37mph. Dropping to 15p will drive your rpms up but only gain you 1 or 2 mph IMO. as far as comparing Hot rods to boats. I have never seen a 302 run high RPMs up hill for 30 minutes without shifting into a lower gear and dropping RPMs. A boat motor is ALWAYS under Load.... That is why they slow down so fast when you come off the throttle. Run that motor over the recommended WOT RPM range too long and your next post will be an engine rebuild.

Like QC said look into TRIM tabs, they will allow you to plane at slower speeds.

 

[Robbabob]

Re: Heavy Boat, need advice

I like going with SS and and maybe dropping to the 15P. You'll eliminate the slip of the damaged blade (which will reduce RPM) and also the added flex the AL gives under the load you're giving it (also reducing RPM). Good chance you'll wind up in the 4,800 to 4,900 range with the new prop; oh, hole shot and top speed will both improve.

Enjoy!

 

[rrhodes]

Re: Heavy Boat, need advice

If he is getting 4700 with a damaged prop a 15p would more than likely throw him over 5200rpm... If you go that route make sure you buy from someone that has a prop exchange program just in case.

 

[hblair]

Re: Heavy Boat, need advice

I want better hole shot to pull tubes, skiers, etc.

rrhodes, what would be the point of listing the engine modifications? So you can critique as to whether my hp estimation is correct? I don't have time for that. The boat has about 280-300hp.

Guys, all I said is that a 302 is capable of much more than 300hp, easy. I didn't say "hotrod engines in boats are a great idea" I know the difference between a hotrod engine and a truck/boat engine.

My boat HAS trim tabs. I use them too.

When I said my prop is beat up, I thought somebody might pay attention to that and understand that this prop is slipping to some degree. I think a large degree. I think with a new, clean 17 pitch prop, it would be too much gear on the engine.

Look at this thing...
http://www.blairautobody.com/Heaths stuff/seaquest/100_0041.JPG
Big, heavy boat...
http://www.blairautobody.com/Heaths stuff/seaquest/100_0042.JPG


I ordered a 15 pitch last night. We'll see what happens here in a few days.

 

[Robbabob]

Re: Heavy Boat, need advice

If he is getting 4700 with a damaged prop a 15p would more than likely throw him over 5200rpm... If you go that route make sure you buy from someone that has a prop exchange program just in case.

Good input.... My logic is as follows:

Damage prop will slip and create higher RPM.

AL prop will flex under the given load and HP causing higher RPM

New SS prop will dig more water, now lowering RPM.

Going with a lower pitch to increase the rpm loss described above seems right to me.

If future prop damage is likely, go with a new AL 17P.

Good luck!

 

[rrhodes]

Re: Heavy Boat, need advice

rrhodes, what would be the point of listing the engine modifications? So you can critique as to whether my hp estimation is correct? I don't have time for that. The boat has about 280-300hp.

No reason to get defensive, I simply asked for details on the build because a properly built performance marine 302 could easily exceed the stock 5000 rpm that a stock motor is designed to run. The 15p will definitely increase your hole shot, Just not sure what it will do on the top end. I never said I did not believe you.....

Good input.... My logic is as follows:

Damage prop will slip and create higher RPM.

Thank you, I was thinking a damaged prop would spin slower but I guess that would depend on the type of damage. Learn something new every day.

 

[dazk14]

Re: Heavy Boat, need advice

Seems to me a 15 pitch 4 blade would be a good place to start. Better hole shot, lower planing speed. An Amita 4 blade Al. is short money and has a quality blade geometry . I have a hard time seeing a 3 blade maintaining a low enough planing speed, and attitude to make it useful for many watersports.

Gorgeous boat!!

 

[QC]

Re: Heavy Boat, need advice

I want better hole shot to pull tubes, skiers, etc.

Thank you.

rrhodes, what would be the point of listing the engine modifications? So you can critique as to whether my hp estimation is correct? I don't have time for that. The boat has about 280-300hp

But you expect us to have time to figure out that you don't expect too much from an otherwise barely 200 hp engine combo? Sorry, but we're skeptics that also want to help. Seems reasonable for us to ask questions.

Guys, all I said is that a 302 is capable of much more than 300hp, easy. I didn't say "hotrod engines in boats are a great idea" I know the difference between a hotrod engine and a truck/boat engine.

But . . . how in all that is reasonable did you expect us to know that?

My boat HAS trim tabs. I use them too.

But . . . how in all that is reasonable did you expect us to know that? If all you wanted was hole shot, and you don't want to have "too (little) gear" then we need to ask/confirm right?

When I said my prop is beat up, I thought somebody might pay attention to that and understand that this prop is slipping to some degree. I think a large degree. I think with a new, clean 17 pitch prop, it would be too much gear on the engine.

You see this is why engine performance and configuration is important. It is not "too much gear" if we have an engine that was built as a Marine engine, and since you know better then you should also know that a 15 is going to lead to overspeed at WOT, so how in heck could we in good conscience recommend that regardless of your need for better hole shot.

I ordered a 15 pitch last night. We'll see what happens here in a few days.

It will have better hole shot . . .

If I approached every thread I responded to here assuming what you left out was unimportant I would give bad advice 99% of the time. I'm not looking at you, I don't know your background, I can't read your face, I can't see your prop, I can't assume you have trim tabs or even know what they are for. Trust me, we get a lot of those here. We also get 100s of street rodders telling us that they can run street specs in a boat all year long. Literally 100s . . . We have to ask. Not to help ourselves, but to responsibly help those who post here. It's just part of the deal.

Rant off. Love you. No really See the smiley right there . . .

 

[hblair]

Re: Heavy Boat, need advice

I thought I'd be sure and give you guys all the info you'd need by reading the "read this first" topic and digging up and including every bit of info it said I should give, in exactly the order it said I should give it. Here's your list...

1) Performance issue you are trying to correct.
2) Current prop manufacturer, model, aluminum or stainless as a minimum.
3) Current prop diameter and pitch (required).
4) Wide open throttle RPM and speed with an average load (very helpful)
5) Engine/drive make, model, year, and HP
6) Boat make model, year, length and weight

Here's what I gave you...

1) Boat is slow to plane, have to roll onto throttle. I want more hole shot for sure.
2) Current prop is a well worn michigan wheel 217 cup aluminum
3) Current prop 15" diameter 17 pitch
4) Wide open throttle 4700 RPM at 32 mph (keep in mind, prop is well worn, one blade has 1/2" of tip bent
5) Engine is a ford 302 producing 280-300hp, out drive is an 898 (chev unit), which I believe has a 1.65 to 1 ratio
6) Boat is a 1988 Glasstream Seaquest 26'. I'm not exactly sure about the weight, but it is heavy.


Apparently, the list needs to be updated.
I updated the list for you guys,to go along with the spirit of the forum. Just get the admin to cut/paste this for you...

1) Performance issue you are trying to correct, and why the heck you want to correct it!? Also, DL#, SS# of all potential skiers, tubers.
2) Current prop manufacturer, model, aluminum or stainless as a minimum. (if you're to poor to afford a titanium unit)
3) Current prop diameter and pitch (required) & your mothers maiden name.
4) Wide open throttle RPM and speed with an average load (very helpful), how much does your wife weigh? (photo of wife on scale required)
5) Engine/drive make, model, year, and HP, and what makes you think you are qualified to know the HP anyway!?
6) Boat make model, year, length and weight (photo of title and bill of sale required)
7) Do not get short with us or we'll be required to tell you how we have to deal with crazy unreasonable people all the time.



There you go

 

[emoney]

Re: Heavy Boat, need advice

You tend to make lots of friends easily, don't you?

 

[Mac525]

Re: Heavy Boat, need advice

OK stock wot for an 1988 marine 302 is 4000-4400 so your 17p is at the very high end for "stock" red line. If this is when the boat is unloaded and almost out of gas then the 17p is looking fine. As stated above more info is needed to help with your setup and useage. Tabs are a great tool when used for the right reson in the right way, they can also have some adverse affects when wake boarding of this is why you want a faster hole shot. The 302 is a great motor that can be made to put up some impressive numbers in the rpm ranges for marine use.

OK for some reason the last four posts did not show up when I posted this wierd ...
we stilll need to know what wot rpm you are trying to get its the big question that you have not answered. Is it balancned and blue printed. does it have roller rockers and lifters.

 

[hblair]

Re: Heavy Boat, need advice

Don't shoot the messenger. I'm here to help.

 

[hblair]

Re: Heavy Boat, need advice

Ok guys, sorry for coming across the way I did. I went back and read this thread and I WAS overly defensive. My bad.:redface:

Anyway, I got the boat out yesterday with the new prop 15 pitch x 15" diameter. I had 9 people in the boat, about 1325 lbs worth. Full tank of gas (65 gallons).

I was surprised with the results.The boat planed effortlessly and at full throttle ran 37mph downstream at 4700rpm. Upstream and into a headwind full throttle, 32mph at about 4700. The boat cruised 28-30mph at 4200rpm.

The old prop apparently was slipping as bad as I thought.

I am very happy with where I'm at here performance wise. I'm glad I took a chance powering the boat with the 302. The boat originally had a 350 chev in it. I bought this boat almost two years ago for less than a thousand dollars. It had no engine or outdrive in the boat. The guy threw in this boat-anchor 302 (seized beyond comprehension) and an 898 outdrive. I've been learning all about mercruisers and 302's ever since. :facepalm:

To answer about the engine modifications, the engine was bored .030, has a cast iron 4 bbl intake, edelbrock 1409 carb, lunati voodoo cam(don't have the specs here) engine builder wasn't keen on going roller rockers as far as the bang for the buck. He said I was at 280-300 hp. I'm thinking I'm prolly at 280hp, I'm still running the points ignition. I'll prolly be addressing that soon. Anybody got an ingition system they'd recommend to me?

Thanks again for the help.