1989 Force 125 on 89 Arriva 19.7 ft. bowrider

[Glenn Iverson]

Just picked this up last week. Tried it out for first time & noticed engine rpm would barely get to 4000 WOT & top speed was 30mph trimmed out. (two people in boat)
Motor seemed to run good but a little rich. Noticed the prop was a 19 pitch. It was really slow out of the hole & towing a tube was almost boring for the kids.It seemed to work hard & after running some prop pitch tools I found out it was over propped. Swapped out the prop for a 15 pitch & ran a can of seafoam through it. Motor is much fasterr out of the hole & sounds a lot happier & tops out around 5000 rpm trimmed out at 26 mph. Specs for this motor call for 5000-5500 WOT. I can now tow a skier no prob but for some reason the top speed seems low to me even though everything else seems to have improved.I am aware that I gave up about 5 mph for better holeshot but still seems low. I have not linked & synced carbs yet nor adjusted timing. The Arriva is a big boat for this motor so just wanted to find out if these readings are actually out of whack before I start to tinker. Boat is in good shape with new floor & upholstery & cant see any obvious signs of rot or foam saturation to weigh it down.

 

[Jiggz]

I have the same motor on a 19 ft ski boat with pylon. I have the,17P stainless prop and top speed with two people on board is around 38~40 MPH on gps at around 5000~5200 rpm. Things you might want to check before doing anything else:
1. I use NGK BUHW spark plugs. For some reasons I get more wot rpm using this plugs
2. Air-fuel idle mixture screw set at 1 turn out from lightly seated
3. Make sure the throttles goes horizontal at WOT position
4. Make sure you use 50:1 fuel oil mix ratio
5. Make sure you are trimmmed accordingly

 

[jerryjerry05]

Welcome.
Do a compression and spark test.
All cyl. need to be within 5-10# of each other.
All plugs burning the same?
​Check the fuel pump diaphragm.

Jiggz's 17p stainless is about the same as a 19p aluminum.

Your original setup is probably right just need to figure out the rpm problem??

 

[SkiDad]

You should be getting at least 35 mph with that 15p set up. Are you using a GPS to gather your speed or using the dash speedometer.

 

[Glenn Iverson]

Did a link & sync of the carbs. They were only 3/4 open. Now they are 8/10's open. Idle stop screw is all the way out so can't open the butterflies anymore without increasing the idle. New plugs. Old ones looked fine. Bottom 3 were a bit wet but not too bad. Top one was clean which is probably typical being closest to the thermostat. I'm also running a telltale if that makes a difference. By looking at the plugs I'm not worried about messing with the timing. I feel better if I'm a bit rich. No compression test yet. (Don't really want to know if u know what I mean) Idle mix screws are 1 full turn out. Top rpm is now around 5200 trimmed out at around 28 mph with my 15 pitch prop with 3 people in the boat. A bit of a shudder at mid rpm that also presents itself as a brief bog out of the hole. I understand this is where high speed jets try to take over from low speed jets. Not sure what to do about it but overall I am very happy with the results. The motor is pushing 30 years old so I am not expecting perfection. Again thanks a bunch for your wealth of info to this newbie to all those who posted.

 

[jerryjerry05]

High speed jets take over anywhere after the idle point is passed.
​The motor even at 30 should run as good as a new one.
The butterfly's can actually go past level.
Try the link and sinc again.

5200 is better but it should turn the 15p at 6000+
Do the comp test.

 

[Glenn Iverson]

OK will do. If I do the comp test is there someway I can jump the starter as I am by myself when doing it so I can still read the gauge?

 

[pnwboat]

I use a remote starter switch similar to the one shown. Just clip one lead to the small yellow wire on the starter solenoid. The other clip goes to the large battery cable that goes back to the battery (not the one that goes to the starter itself) on the starter solenoid. Just press the switch, and the starter will engage.

NOTE: Make sure the prop is clear of anything. If the throttle is in a position to engage forward or reverse, the propeller will turn. Attaching the remote starter switch directly to the starter solenoid, by-passes the neutral safety switch.

 

[Glenn Iverson]

Found the problem no wonder I couldn't tune the idle adjustment, looking at the terminal block on the left side of the engine the small #1 green trigger wirehad broken off. No wonder number one cylinder looks so clean it was never firing in the first place. Once it was repaired I now have RPM's beyond where I want to go with my 15-inch prop. I've had it up to 5500 RPM at 32 miles an hour I know it it'll go to 6000 if not more. Shudder and hesitation are gone and hole shot is amazing. Hopefully my gas consumption will improve now because it was smoking so bad now I understand all the gas that was dumping. That has greatly improved as well.

 

[SkiDad]

that really good to hear ! - if you are just pulling tubes a 17 is probably the best pitch. If you ski alot the 15 will really help. It depends which lower unit you have ?? Does it have any numbers like 3 or 4 stamped on the side by the vent hole ? is it dual exhuast or single ? There were 3 different gear ratios made.

You won't hurt anything to see what rpm you hit for a few seconds on the 15. I've had mine up to 6200 on a cold day with an aluminum prop. My current prop is a 15 stainless that turns 5400-5500 with my normal load. A 15p AL i had was hitting 5800 regularly so I gave it to someone.

 

[Glenn Iverson]

I agree 17 pitch would be a happy medium for that boat. The lake is not big so 40mph cruising is not realistic. But for waterskiing & tubing that 15 pitch prop is great on the holeshot & still more power than a average skier can handle. Probably just keep it at 5000 rpm to be safe & still plenty of power to tow. I still have my original 19 pitch prop that I will install if I wish to venture onto some nearby large lakes. I have the 1.73 lower end with the single exhaust.

 

[SkiDad]

Sounds like it's running really strong. I could never turn that much RPM with the 1.73

 

[jerryjerry05]

Welcome.
Do a compression and spark test.
All cyl. need to be within 5-10# of each other.
All plugs burning the same?
​Check the fuel pump diaphragm.

Jiggz's 17p stainless is about the same as a 19p aluminum.

Your original setup is probably right just need to figure out the rpm problem??

​Compression and spark test.
First step in any diagnosis.