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SUBJECT: # 27651: 150 HP Johnson- Can't get up to WOT
Submitted by TimL (71.235.220.165) from CONNECTICUT on 8/3/2006 9:29:00 PM
I am thinking of selling my boat package, HydraSport 1850 Vector with 1994 Johnson 150HP. Took fellow for ride last night, 90 degrees, high humidity and couldn't get motor over 4700 rpm's. Normally I can't get past 5100 rpm's. I am running an OMC stainless prop, 14 3/4 x 17. What is my next step prop wise to get closer to the WOT of 5500, Defenitely need help with the hole shot. We did a compression test and it was 110,105,105,103,105,105, That seemed in line for a motor with 800 hours that's been decarbed regularly. Any help would be appreciated. Fellow backed out because he thought engine was tired. Any help would be appreciated.
- 8/4/2006 7:58:00 AM
Submitted by
Dwight (68.45.241.239) from PA says Lower RPMs
First thoughts are: Was there H20 in the bilge, is your hull clean? Relpace your plugs just in case. If not then maybe the ETOH in the gas has led to a partially plugged carbs or fuel line/filter so check them. Good luck
- 8/5/2006 6:01:00 PM
Submitted by
Alex from GA (66.168.200.77) from AL says RPMs
Boats really hurt, in the speed department, when you add weight. Did you take a big guy and do you fish alone when you're running 5100? Usually there's about 200 rpm difference per inch of prop so a 15" prop will bring you up to 5100 rpm and get you on plane much faster. A 15" prop seems pretty short to me with a 150 that's running good so I would make sure the engine is up to snuff first.
- 8/5/2006 9:24:00 PM
Submitted by
Sal (71.159.217.193) from CA says Not the prop.
That 150 on that boat should have no problem at all twisting a 17p prop to 5500 trimmed out. Something else is wrong there. I would raise the engine up 1 set of holes & see where the rpms go. Did you trim the engine out when testing rpms ? If not, you need to. If trimming out & raising the engine dosen't get you up to 5200 rpms you need to bring it in & have a tech test it because a 150 hp on an 18' hydrasport should get much better than that. Do you have a large cabin or "T" top? Sal
- 8/6/2006 3:16:00 PM
Submitted by
TimL (71.235.220.165) from CT says RPM's
This is the Vector series which is a deep V and heavy for a 18.5'. I probably could come up another set of holes on the transom. I am going tonight with my wife for a quick fishing trip. I'll see if it does much better with less weight. Thansk for the input.
- 8/6/2006 4:00:00 PM
Submitted by
TimL (71.235.220.165) from CT says Sorry Sal, No T top
Any comment on the compression readings? I didn't think those were too bad for an engine that is 12 years old with 800 hours. One fellow that looked at the boat said it was way too low and my motor could die any moment. Of course, he said that right before throwing a low ball offer.
- 8/7/2006 7:52:00 PM
Submitted by
Dunk79 (69.249.201.219) from NJ says Heat....
Last week was brutal with heat and humidity and that can take 3-400rpms off any engine.. Thing is I agree with Sal that engine on a 18ft HSP Vector should twisting a 19" wheel at those rpm's.Need to hear some honest speed numbers??
The compression numbers sound fine to me.
Tim, a buddy of mine in Fl has the 17ft version with a 90' GT150 Johnson crossflow and it's runs 56-58mph all day long at 5800. Of course he did work at the OMC test center in Stuart and no doubt the engine was "tuned".... But on the flip side your engine is a 60 degree looper Eagle block and they put out their best power at 52-5300 and have lots more punch than the old crossflows.
Speed? If I wasn't seeing a solid 48-50mph out of that rig...and the engine running right I'd be looking at the bottom of the boat for serious problems. Maybe a major hook?? Does she trim up? You should be able to fly that boat with a V6 prop and that engine..
- 8/9/2006 11:48:00 AM
Submitted by
TimL (64.252.95.57) from CT says Speed
Dunk, Thanks for the response. Remember this is the Vector hull and it runs real deep. At WOT which is 5200 on a good day, 17P gives me 36-38 on the GPS by myself with a 1/4 tank of fuel. The boat has a 82 gallon tank and I never fill it up beyond 1/2. A couple nights later with my little wife on the boat I was able to get it back up over 5000 rpms and of course this time the temp was in the low 80's instead of the 90's. Should I be looking at anything else. I didn't think my compression numbers were too bad for the year and hours. I can trim up abit but end up cavitating. Not sure how much I should be using the trim tabs in this equation.
- 8/11/2006 11:36:00 AM
Submitted by
beachblitz (205.148.53.200) from NJ says for comparison
I am not an expect or very knowledgable, but for comparison, I'm running a '99 150 hp Johnson with the same prop on a 20'6" wac, hull weight 2400# dry no motor, 18 degree deadrise, 8'9" beam, with 50 gals. fuel, two adults and alittle more gear than I need and my WOT numbers are around 42-44 gps mph @ 5200 rpm, motor trim up to almost cavitate, no tabs on glassy water. That's a summer day in Joisey with 80-90 degrees and higher humidity. I don't think I can get much better. Maybe you give up alittle speed to greater deadrise, weight or tabs.
