new engine

#1 07-16-2006, 03:00 AM

i have a 1989 v20 steplift with a new 225 h/p jasper i/o that i am not very happy with because it does not preform as well as my origanal merc 165 h/p i/o i used to get about 42 m.p.h. with the old engine but now with just 2 people i can get max 31 m.p.h the old one through a rod and cracked the block one day or else i would have kept it. i did not choose this engine my mechanic said was a great engine and to trust him. It is a reliable engine but not a powerful engine. is somthing wrong with the engine or is there a way to get more power out of the engine.

p.s. this is my first time posting

rb437 · #2 07-16-2006, 11:21 AM

You sure about that 41 mph? Best I've ever done is about 36. Anything else change? prop? outdrive? are you getting max rpm's

reelapeelin · #3 07-16-2006, 01:37 PM

Jasper has a pretty good warranty if I'm not mistaken...If you feel like you're gettin' the straight scoop from your mechanic, have him check out the motor thoroughly, including compression testing all cylinders...If you feel the need, take it to another mechanic and have him test same (or you can get your own compression gauge and bone-up on how to test)...w/more HP, there also may be a need to change props, but to tell you the truth, you'll have to get that from someone more knowlegeable of I/O drives...

You're postin' speed comparisons, but are you gettin' the same, better or worse RPMs from the new motor as the old?...

Seacrets · #4 07-16-2006, 08:22 PM

Start at the prop. What's your wide open throttle rpms?

captbent · #5 07-16-2006, 11:02 PM

I REBUILT MY 470 AND ON FLAT WATER 45 MPH 2 MEN AND GEAR AND A 3/4 FUEL. SLOWER IN A CHOP OUT ON THE OCEAN 35-40 MPH THATS WHAT MY GARMIN GPS SAYS IM DOING BUT I LIKE TO RUN ABOUT 30 MPH SMOOTH AS CAN BE

captbent · #6 07-16-2006, 11:03 PM

AND A STOCK PROP AND NEW OUT DRIVE

Skools Out · #7 07-17-2006, 01:13 AM

first thing check the timing. make sure it's advancing. Timing is usually set at 36* advanced.

#8 07-17-2006, 02:26 AM

my r.p.m. would top out a 4500 with the merc but now i am lucky to get 3800 (i am not sure about the max rpm on the jasper) and when ever i do the temp rises from 155 (which is how hot my old engine would get at top speed) to about 190 F. i have never changed the prop with the new engine i changed it about 2 years ago with the old engine. I dont know if this makes any difference but the lower unit has about a 4 inch crach in it that i noticed after the new engine was installed would this make any preformance differences. i would use another mechanic but i keep my boat a a marina and they are right at the marina and because of that they are much cheeper for labor other wise i would have had sombody else replace my engine. My g.p.s. said 36 knots i think if my math is correct that should be 41 42 mph.

#9 07-17-2006, 02:38 AM

I had a 165 I/O years ago in an old v-20 and I was lucky to get 30 mph on a flat day with two guys and I thought that was about par for that engine and weight combination.... Frank

reelapeelin · #10 07-17-2006, 04:22 PM

fishbone, find out what max rpm for your new motor is as recommended by Jasper...that's what you're shootin' for when "proppin" your motor...

...a 4'' crack in your lower-unit could be VERY signifigant...do what you gotta(repair or replace) on that issue and while you're at it, you probably wanna put new water-pump in it...

You may also need a thermostat that allows more water flow, too...