Logo
FULL SITE MENU

I got it

E

ejbtech1

Regular Contributor
"I took my boat out today, and

"I took my boat out today, and goofed around with it.
I just got to the point that I realized that my boat won't do over maybe 10 mph. 4 cylinder in a 21 foot boat......
NOT TRUE!!!!!! I retarded my timing to the fullest extent and gave her full throttle!! BAM!
I am off on the timing! This boat picked up to 4500 rpm and did at least 35 mph!
The prop did most of the trick, but I have been off on my timing all along. Go figure. unfortunately I chewed part of my new prop up on the ramp when I pulled my boat out of the water.(Left my outdrive down) DUH!!!
But, I just wanted all to know that this little 4 banger pushed my 21 footer up on plane and to about 35 mph!!!!! I am exstatic!!!!"
 
"Well, Eric. I'm glad you

"Well, Eric. I'm glad you finally got it running and well (I guess you finally decided to get hold of a timing light)
wink.gif
. But now you are making me feel guilty for having a 307 HP engine installed on a 22' boat and doing marginally more speed than you do. Oh well.
biggrin.gif


Don't feel bad about your new prop, I must have left 3 or 4 at the ramp during the last few years for not litfing my VP outdrives due to CRAFT (Can't Remember A Frigging Thing) disease.
wink.gif


And now that you are getting things under control, is perhaps the time to try a 15 x 15" and see ow it goes?"
 
"I think I need to save my pen

"I think I need to save my pennies for another 14x 15 the way its going......
What do you think a 15x15 will do for my performance?
I was actually shocked.
I put this boat in and just expected to do about 10 mph, which I did, to a local restaurant on the lake! Had some lunch......(And a few drinks)
When I got back out, the boat acted weird, so I messed around with the timing, and then BOOM!!!! There it was.
Unfortunately, I did have a timing light, but forgot to get a white paint pen to mark my crank pulley. So I couldn't actually use the light. I just moved it all the way advanced, that made it worse. Then, I said screw it and retarded it all the way. That was the trick.
I intend on timing it right, but obviously I am a tooth off. Or close to it. Retarding it made it close to where irt should be. My boat came alive!!!!!!
I stuck at around 4000 rpm and I did about 30-35!!!! She never got over 210 in temp and planed out!! I did move the trim pin to the closest hole to the transom.
Funny, cause I was actually thinking of selling this boat on my way to the restaurant.
biggrin.gif
"
 
"A 15 x 15" (if your e

"A 15 x 15" (if your engine can handle it) will not give your boat more speed but will give more thrust, which you will likely need when going on the plane and when in rough weather or strong wind against.

I find it interesting that you had a misbehaving boat and, once you thought of selling it, it started acting nicely. I wonder if your boat could actually read your mind. (just kidding)
biggrin.gif
"
 
"A pscho, um psychic boat?!?!?

"A pscho, um psychic boat?!?!?!? HMMMMM.
Kinda like the movie christine!!!!
rofl.gif

I think I had a combination of the wrong prop and ignition timing. Both seem to make a boat slow if they are wrong. I knew that timing could be an issue, but the prop thing was definately off. Thanks for the help. This boat would have been scrap if it weren't for your advice!!!!"
 
"Sorry, but a little 'salt

"Sorry, but a little 'salt' seems to be needed.
4000rpm and gear ratio of 2,15;1 (if correct drive), should give around 23knots without 'slip' or 18-20 at the best 'true', or some 23+mph with a 15" pitch prop. I suggest You not only do an ignition timing check, but a rev-counter check as well.
If You want to keep it running a timing belt replacement/check is also recomended for those engines, and take special notice of the condition of the crank-shaft timingbelt gear when it comes to corrosion."
 
"'I stuck at around 4000 r

"'I stuck at around 4000 rpm and I did about 30-35!!!! She never got over 210 in temp and planed out!! I did move the trim pin to the closest hole to the transom.
Funny, cause I was actually thinking of selling this boat on my way to the restaurant.'

Did I?"
 
"Eric, I don't think that

"Eric, I don't think that Morten has gotten the wrong post. He is just saying that it is physically impossible that your boat did 30-35 miles with your engine, outdrive and prop. And I have to say that both math and physics support Morten's statements, unless you had both a 10 knots current and a strong wind in favour at the time. Oh well, the important thing is that the boat planes and that you are happy with the results.
biggrin.gif
"
 
any chance thats a volvo 4 cyl

any chance thats a volvo 4 cyl because i found that timing can be a little more triky than that. if not enjoy
 
"ok whatever. Weird that a neg

"ok whatever. Weird that a negative post can come from such a positive website. But that is ok. I am happy with the results, and I will continue to post here.
Yes Alan, it is a volvo 4 banger. I have been messing with it for over a year and finally made the boat come alive after sitting for six years out of the salt water.
I installed an electric fuel pump with a pressure reg. and electronic ignition, took the old marine engine out, and installed an automotive engine with marine head and intake/exhaust. Been a trick, but she runs and now I can say she runs well.....
sun.gif
"
 
"I do not quite understand wha

"I do not quite understand what You find negative.
One of the reasons for the post was to even inform others that lurks around and have prop/speed questions an idea of what kind of speed is obtainable with which prop and which engine at what rpm.
we, on the 'advicing' end of this board, does our best to give as correct info as possible."
 
"I JUST KNOW WHAT I KNOW......

"I JUST KNOW WHAT I KNOW......... I DID WHAT I DID AND GOT WHAT I GOT. I AM GIVING CORRECT INFO. TOOK ME A WHILE, BUT I AM PROOF THAT THESE THINGS CAN BE ACHIEVED. NO FALSE INFO ON THIS END."
 
"No one is accusing you of &#3

"No one is accusing you of 'FALSE INFO' but simple mathematics states clear that someting is 'wrong'.

IF You are getting 30-35 miles at nowind-no current situation = Your tach is wrong.


IF You were running '4000RPM'= Your 'speedometer' is wrong.

I normally uses below formula:


<u>RPM x PITCH" x 60(min) x 0,0254</u>
Gear.ratio x 1852
= Speed in knots (theoretical).

If You want it in mph, replace 1852 with 1650 (conversion from meter/kmh).
The prop slip percentage is normally between 10 - 25% depending on boat, speed, prop type etc. To get the estimated TRUE speed, multiply the therortical by 75 - 90%. For Your boat and relitive small blade area and 'low' speed I would estimate the slip percentage to be around 15-18%.

PS: Drop Your 'caps lock', not very polite."
 
"Morten Ringvold - Thanks for

"Morten Ringvold - Thanks for the formula. I've been looking for one to estimate mine. However, I'm wondering why there is not a mention of blade dia / # of blades (cup %, aspect ratio, ?). Or, does this become to complex for estimating.

Thank you"
 
Back
Top