What makes a marine engine a MARINE engine

[BigBoatinOkie]

Re: What makes a marine engine a MARINE engine

Sooo, are you looking to replace/rebuild your engine because it's tired or because of poor boat performance?

A little of both. I've been having trouble achieving the proper rpm range for the props I have. I've discussed props extensively in the prop forum. Based on the the prop I have now(18p alum 4 blade) I should be operating in the 4400-4600 rpm range. I'm only able to achieve about 3800-4000 rpm. Also the boat is quite slow to plane, and in my opinion a 4-blade 18p should get me outta the hole pretty quick. When I bought the boat, it was fitted with a ss 22p, which I would assume worked well for the PO at some time. It took forever to plane with that. Then I went to a ss 20p and it helped a bit. And now the 4-blade 18p. I could not reach recommended WOT RPM with any of the props. Like I said before, the trim tabs will help a lot, but I believe the engine is getting tired. I have not done any diagnostics on the current engine yet, and I figured if I was going to have to tear into it, I might as well swap to a better engine. But I'm still trying to listen to different angles and make my decision after some discussion with other boaters.

 

[BigBoatinOkie]

Re: What makes a marine engine a MARINE engine

270win
You seem to be giving a lot of advise for someone that really doesn't understand marine engines that well. You may know a lot about the automotive side and racing, but I don't see any knowledge showing through about the marine side of things. And that is what this forum is about. MARINE, not GTO's and race engines. So just be careful what you are saying. You haven't given any thought about reversion have you?

Don my man, we're just having a discussion here. I believe 270Win has given some quite good advice. Mostly he's advised me to play it safe and go with marine specific equipment. May not agree with everything, but that's why we discuss it. I appreciate any and all advice and ideas. I'm so glad there's a place where we can all learn from each other, even if sometimes someone may not have the right idea. Go easy on the guy, he's tryin to help, just like you've helped so many, including myself. As a matter of fact, in this thread about the differences between auto and marine engines, the majority has said that there is little difference in the two, so that must mean that GTO and race engine knowledge still applies.

 

[270win]

Re: What makes a marine engine a MARINE engine

A little of both. I've been having trouble achieving the proper rpm range for the props I have. I've discussed props extensively in the prop forum. Based on the the prop I have now(18p alum 4 blade) I should be operating in the 4400-4600 rpm range. I'm only able to achieve about 3800-4000 rpm. Also the boat is quite slow to plane, and in my opinion a 4-blade 18p should get me outta the hole pretty quick. When I bought the boat, it was fitted with a ss 22p, which I would assume worked well for the PO at some time. It took forever to plane with that. Then I went to a ss 20p and it helped a bit. And now the 4-blade 18p. I could not reach recommended WOT RPM with any of the props. Like I said before, the trim tabs will help a lot, but I believe the engine is getting tired. I have not done any diagnostics on the current engine yet, and I figured if I was going to have to tear into it, I might as well swap to a better engine. But I'm still trying to listen to different angles and make my decision after some discussion with other boaters.

Assuming this is in the 18' Wellcraft?

I would also check everything listed HERE.

A healthy and properly set up 305 should be pretty strong in a 18' runabout.

We had a Chaparral 198XLC with a 5.7 Merc (260) that ran 58mph and would pull two skiers with no problem...IIRC we ran a 19P 3 blade aluminum prop.

 

[270win]

Re: What makes a marine engine a MARINE engine

Don my man, we're just having a discussion here. I believe 270Win has given some quite good advice. Mostly he's advised me to play it safe and go with marine specific equipment. May not agree with everything, but that's why we discuss it. I appreciate any and all advice and ideas. I'm so glad there's a place where we can all learn from each other, even if sometimes someone may not have the right idea. Go easy on the guy, he's tryin to help, just like you've helped so many, including myself. As a matter of fact, in this thread about the differences between auto and marine engines, the majority has said that there is little difference in the two, so that must mean that GTO and race engine knowledge still applies.

Thank you...

 

[BigBoatinOkie]

Re: What makes a marine engine a MARINE engine

quite welcome. it is indeed an 18' bowrider. I think I need to slow down a bit and give my 305 a good once over and get the trim tabs fixed and run it for another season. Wish I would have done a compression test while it was still in the boat.

 

[270win]

Re: What makes a marine engine a MARINE engine

quite welcome. it is indeed an 18' bowrider. I think I need to slow down a bit and give my 305 a good once over and get the trim tabs fixed and run it for another season. Wish I would have done a compression test while it was still in the boat.

I think that's a good plan of action. Is it on an engine stand now? If you haven't already torn it apart, you could still do a compression and leak-down test to determine the health of the cylinders and the valve-train.

 

[BigBoatinOkie]

Re: What makes a marine engine a MARINE engine

I have not torn it apart yet. It's sitting on a little dolly that I made.

Here's what I've got going on right now. Got my hands full, but this is in the restoration forum.

 

[bruceb58]

Re: What makes a marine engine a MARINE engine

If you don't know what "reversion" is in a marine engine, you shouldn't be giving advice about what types of cams to use.

You use a cam like 270win says to use and you are going to be sucking water big time.

 

[4bait]

Re: What makes a marine engine a MARINE engine

Pretty much any engine can become a marine engine.

The main difference will be the cooling system in Particular the water cooled exhaust manifolds.

i'm currently converting a series 2 fuel injected buick V6 which can be good for 300 plus Hp

cheers Andy

 

[270win]

Re: What makes a marine engine a MARINE engine

You use a cam like 270win says to use and you are going to be sucking water big time.

What is it about that grind that will cause the motor we were discussing at the time to "suck water big time"??? It's basically a MerCruiser 5.7 grind...maybe they could learn something from you.

 

[270win]

Re: What makes a marine engine a MARINE engine

I have not torn it apart yet. It's sitting on a little dolly that I made.

Here's what I've got going on right now. Got my hands full, but this is in the restoration forum.

wow! That's an area I need help with when I get my engine out next month...

Is the dolly your engine is sitting on stable enough to turn it over with a wrench on crank bolt with the plugs out? If so, you can do a compression and leakdown check. Have you ever done that befor?

 

[Alpheus]

Re: What makes a marine engine a MARINE engine

I bought one of these and welded a couple more gussets on it and use it as a run up stand.

http://www.northerntool.com/webapp/...88_406688?cm_sp=RVC-_-Product Page-_-Products

 

[bruceb58]

Re: What makes a marine engine a MARINE engine

What is it about that grind that will cause the motor we were discussing at the time to "suck water big time"??? It's basically a MerCruiser 5.7 grind...maybe they could learn something from you.

Well in one post you are talking automotive cams in GTOs and another post you are talking something else. Since you don't know about the hazards of reversion and how certain cam profiles can cause this to occur, you need to be careful giving advice to people who may take your advice and wipe out their motor.

If you have too much overlap and the exhaust valve is still slightly open as you start the intake stroke, you can suck water in. This will basically happen at idle.

 

[Alpheus]

Re: What makes a marine engine a MARINE engine

Reversion can also happen with just the resonant frequency of the engine at certain RPM's causing the water to travel upstream through the exhaust valves and into the combustion chamber. This is one of the reasons you should stay away from the "el-cheapo" risers...

 

[270win]

Re: What makes a marine engine a MARINE engine

Well in one post you are talking automotive cams in GTOs and another post you are talking something else. Since you don't know about the hazards of reversion and how certain cam profiles can cause this to occur, you need to be careful giving advice to people who may take your advice and wipe out their motor.

If you have too much overlap and the exhaust valve is still slightly open as you start the intake stroke, you can suck water in. This will basically happen at idle.

We've already covered this...I know how this works and I think that's been shown. The entire conversation and the comments I'm making are relevant to the topic. If you can't understand how my examples from street engines can be applied to marine engines then that is not MY shortcoming. Do you have anything to add or do you just want to parrot Don or someone else here?

I was asked about reversions, I answered...You made a statement about a cam I recommended that, quite frankly, shows that you have no idea what you're talking about. So, please explain to me what specific aspect of the cam profiles I mentioned would cause water to be drawn into the exhaust port? What would you change about that grind to make it perfect for the application?

This is the second time I've asked you to qualify your challenge to my recommendation...

 

[270win]

Re: What makes a marine engine a MARINE engine

I bought one of these and welded a couple more gussets on it and use it as a run up stand.

http://www.northerntool.com/webapp/...88_406688?cm_sp=RVC-_-Product Page-_-Products

Got any pics of the finished product? I'd like a stand to break in engines on but the ones I find are pretty expensive...

 

[mkast]

Re: What makes a marine engine a MARINE engine

Why is my advice is being scrutinized like this???

Some of your responses (or lack of) raise some eyebrows in a room full of mechanics.
You stated, "I don't buy used engines, is that so hard for you to understand?"
What was in the used boat you purchased?
If you spend some time at: http://www.mortec.com/ you will find auto, truck and one "industrial" engine. Wonder where the marine, generator, forklift and countless other special application engines come from?
I get a lot of mileage out of this one.
What is the minimum number of hours the FAA requires for a pilot to take someone on a flight, not for hire? 40
What is the minimum number of hours the FAA requires for a mechanic to turn a wrench on a certificated aircraft? 1900
You do the math.
You won't be the last individual to have questionable opinions fall out of a keyboard.

 

[270win]

Re: What makes a marine engine a MARINE engine

Some of your responses (or lack of) raise some eyebrows in a room full of mechanics.
You stated, "I don't buy used engines, is that so hard for you to understand?"
What was in the used boat you purchased?
If you spend some time at: http://www.mortec.com/ you will find auto, truck and one "industrial" engine. Wonder where the marine, generator, forklift and countless other special application engines come from?
I get a lot of mileage out of this one.
What is the minimum number of hours the FAA requires for a pilot to take someone on a flight, not for hire? 40
What is the minimum number of hours the FAA requires for a mechanic to turn a wrench on a certificated aircraft? 1900
You do the math.
You won't be the last individual to have questionable opinions fall out of a keyboard.

First, hats off on the A&P...that's an underpaid job no matter how well you're paid...the liability you expose yourself to everytime you sign a log book is a serious thing. So is the fact that when you make a mistake, people can easily be killed by it. Props given...

With that in mind the responses you are leaving are pretty disappointing...

Your comments regarding the time required (FAA minimum) to attain a pilot's license vs. the time required to become an A&P has almost zero contextual
value in this conversation...

The comment about my used boat having a used motor is almost too juvenile to address...let me clarify for those who want to revert to rediculous arguments, when I buy engines (ie just an engine, complete and ready to run) I buy remaned or new...unless i'm buying a core to build my own. I asked you, rhetorically, if that was too difficult for you to understand, but your response seems to verifying that is was...

I'm not sure what you're trying to say about Mortec, but I'm very familiar with the site. You may want to re-read my comments and advice before you come back with more of this....like I said, disappointing...

 

[BigBoatinOkie]

Re: What makes a marine engine a MARINE engine

I'm no mechanic, but instead of wasting time questioning 270Win's knowledge, spend that time telling us specifically what he's wrong about. I'm sure it's true that using the wrong parts can cause damage to the engine, but has he suggested anything to me that is inappropriate or harmful to the engine. If he has, tell us what it was. Complaining about someones knowledge is not helpful in this thread unless you can tell everyone where he's wrong and suggest a more appropriate alternative. So far, all I've heard is complaining. So read all his posts, and please tell us if he has suggested something that's inappropriate for use in a marine engine. I didn't start this thread to get everybody in an arguement.

 

[270win]

Re: What makes a marine engine a MARINE engine

I'm no mechanic, but instead of wasting time questioning 270Win's knowledge, spend that time telling us specifically what he's wrong about. I'm sure it's true that using the wrong parts can cause damage to the engine, but has he suggested anything to me that is inappropriate or harmful to the engine. If he has, tell us what it was. Complaining about someones knowledge is not helpful in this thread unless you can tell everyone where he's wrong and suggest a more appropriate alternative. So far, all I've heard is complaining. So read all his posts, and please tell us if he has suggested something that's inappropriate for use in a marine engine. I didn't start this thread to get everybody in an arguement.

I agree, if I can learn more about some of the differences in marine engine and combine that with what I do know about engines in general that would be great.

Honestly, most of the nay-sayers seem to be more threatened by someone stepping on their "turf" (ie this forum) than getting the best advice to the OP and anyone else who reads this thread.

I can tell you this much, if you guys came over to a car forum and tried to share some of your experience...I wouldn't treat you like this. I says alot about the "experts" here. Some of you have some great knowledge on marine engines, but a few of these responses make me question the kind of people you are...