: Why is my 99 620 so slow?
09-02-2008, 08:56 PM
My '99 Ranger 620 only goes low 40's with a full tank and two guys. Motor is a 225 Opti and is in the 3rd. hole from the top. 21 Tempest Plus blows out in 2-3 footers. Trophy Plus 4-blade does not blow out but only does 40mph.
09-03-2008, 05:13 AM
How many rpm's are you running with these setups at WOT?
unlogged Eric Olson
09-03-2008, 06:11 AM
THe issue you're having is from the boat transom height. On that year it was 23 1/2" your engine is a 20" shaft. Since the transom is taller the engine can't get a good bit, two things that will help
drop the engine as low sa it will go. This will let the prop bite and get lift. That blow out you feel and hear is at a very low trim angle, not good at all since that hull needs bow lift. Mainly because the gas tank was towards the bow in that series of boats.
The other option is to install either a manual jackplate (6") or hydraulic. this will significantly help the performance on this boat.
lowering the motor should get it to 50. With a plate it should run in the mid 50's of course assuming the engine isn't down on power.
I haven't seen your rpms but will wait for further info till you post them.
Hope this helps!
09-03-2008, 01:00 PM
You are so knowledgeable on these types of issues, just wondering if you might be to make a suggestion or two on my situation. This isn't a Ranger but I'm sure the same concepts apply.
I run a 1997 Lund 1775 Pro-V single console, 2003 Johnson 150 hp 2-stroke with a 21 Viper stainless steel prop. Currently, I have it mounted all the way down on the transom.
Performance is 47-48 mph top end at 4900 rpms (fully loaded, half to 3/4 tank of gas) If I trim a little higher the rpms can increase to 5100 but the speed goes down. I've also tried moving the motor up one hole, but that didn't increase performance.
When I first had this motor mounted at the dealer, I ran it on the Mississippi in early spring, downstream, and it hit 52.5 mph (I can't achieve this any longer). I think I understand that weather, humidity, heat, current, etc. are going to impact speed downward; however, I think I should be able to hit over 50 mph consistently.
Are there things I can try to improve my performance? Mounting up additional holes? New sparkplugs? or do I need to go back to the drawing board and look at alternate props?
09-03-2008, 05:41 PM
I can get about 5300-5400 with the 4-blade (13 1/4x21). I have never seen 5700-5800 rpms since I bought the boat. The center of the nose cone is 3 1/2 below the bottom of the boat. I haven't been running the 3 blade since the slight blow out gets annoying. I change the plugs every two years and run quickclean every couple of tanks. The boat would not fit in my garage if I put a jack-plate on the boat.
I would suggest that you take your boat into your dealer and have them put a test prop on your engine.
The test prop is a water dyno and by its use, can calculate the hp being generated by your engine.
For your boat, your performance sounds like you have a 150 hp on your rig, not a 225.
Before doing anything with the motor height, props or anything else - have the motor checked to see if it is developing its rated power. If it isn't - fix it so it is.
If it is developing rated power, have the boat checked for a hook in the hull or some other defect that is causing drag.
You should be doing at least another 15 mph - with that much rated power on the boat.
Once you have verified, that you have a properly performing motor, and once you have verified that you don't have a hull defect - you can start working on other things.
One of the first things that I would do - if the motor is putting out the right power, and if the hull is straight, is to empty the boat of everything.
Take out everything, so that the only thing you have left in your boat is the hull, 225hp motor, one starting battery, and 5 gallons of gas.
No water, tools, livewell water, spare anything and no other passengers or gear.
I would guess that you will likely unload 1000-2000 lbs of weight out of the boat.
Then, take the boat out for some engine rpm tests and gps speed tests.
If you have your prop wrench in your tow vehicle and a half dozen or dozen different props - so much the better.
Without doing anything else to your motor height or other things - simply test every prop - with only you in the boat for top engine rpm, and top - 2 way (up wind and down wind) top speed.
When you are all though - with the correct hp, straight hull, right prop in the right location, you should be able to have increased your speed from where you are to the upper 50s or low 60s.
unlogged Eric Olson
09-04-2008, 10:18 PM
On that boat the engine must be as low as it can get. The 3.5" below pad is not enough to get the prop bite you need to lift the bow. Unfortunately with that setup I believe the lowest you can get the engine is on the 2nd hole. One key thing to look for once you move the engine down-----Hydraulic steering cyl clearance when the engine is tilted. You'll just need to be careful when tilting for launching and retrieving the boat.
If you are somewhat mechanically inclined you can lower the engine yourself. If you like I can fill you in on how to do it.
THe Tempest prop was also a good performer on that boat as it is a bow lift type prop with good speed characteristics.
Just a little reference for you, with an 8" jackplate on the new 620's boats 3.5" below pad will get you best performance and that hull needs much less lift. That's with the fuel tank to the rear, different hull etc.
Drop the engine, get a demo prop to play with it. No cost to you, lets you get the base set-up correct, then proceed from there.
unlogged Eric Olson
09-04-2008, 10:21 PM
SHoot me an email and we can cover most of the details of your set-up then.
09-05-2008, 12:52 PM
I run a 1997 Lund 1775 Pro-V single console, 2003 Johnson 150 hp 2-stroke with a 21 Viper stainless steel prop.
There's your problem.
Too much prop and not a good model prop for your boat.
Try it in 19...or try a 20 Raker.
And after that...move it up a hole
I'm not Eric... but I sold Lunds ...some just like you have, for many years.Your problem is your Prop
09-05-2008, 03:17 PM
TMac, thanks for the response and information.
09-06-2008, 07:53 PM
Thanks for all the great advice. I'm going to take it up to Cabales next week and get the motor lowered and then try the 21 Tempest + on Lake Erie.